Patent Publication Number: US-8528564-B2

Title: Devices, systems and methods using magnetic force systems affecting both the tongue and the soft palate/uvula in the upper airway

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 11/397,744, filed Apr. 4, 2006 now U.S. Pat. No. 7,721,740 entitled “Devices, Systems, and Methods Using Magnetic Force Systems In or On Tissue,” which is a continuation-in-part of U.S. patent application Ser. No. 10/806,372, filed Mar. 22, 2004 now U.S. Pat. No. 7,441,559 entitled “Devices, Systems, and Methods to Fixate Tissue Within the Regions of the Body, Such as the Pharyngeal Conduit,” which is a continuation-in-part of U.S. patent application Ser. No. 10/718,254, filed Nov. 20, 2003 now U.S. Pat. No. 7,360,542, entitled “Devices, Systems, and Methods to Fixate Tissue Within the Regions of the Body, Such as the Pharyngeal Conduit,” which is a continuation-in-part of U.S. patent application Ser. No. 10/656,861, filed Sep. 6, 2003 now U.S. Pat. No. 7,188,627 entitled “Magnetic Force Devices, Systems, and Methods for Resisting Tissue Collapse within the Pharyngeal Conduit,” which further claims the benefit of U.S. Provisional Patent Application Ser. No. 60/441,639, filed Jan. 22, 2003, now abandoned, and U.S. Provisional Patent Application Ser. No. 60/456,164, filed Mar. 20, 2003, now abandoned, and which is a continuation-in-part of U.S. patent application Ser. No. 10,236,455, filed Sep. 6, 2002 now U.S. Pat. No. 7,216,648 and entitled “System and Method for Moving and/or Restraining Tissue in the Upper Respiratory System.” This application also claims the benefit of U.S. Provisional Patent Application Ser. No. 60/739,519, filed Nov. 23, 2005, now abandoned, and U.S. Provisional Patent Application Ser. No. 60/754,839, filed Dec. 29, 2005, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed to devices, systems, and methods for the treatment of sleep disordered breathing including obstructive sleep apnea and snoring. 
     BACKGROUND OF THE INVENTION 
     I. Characteristics of Sleep Apnea 
     First described in 1965, sleep apnea is a breathing disorder characterized by brief interruptions (10 seconds or more) of breathing during sleep. Sleep apnea is a common but serious, potentially life-threatening condition, affecting as many as 18 million Americans. 
     There are two types of sleep apnea: central and obstructive. Central sleep apnea, which is relatively rare, occurs when the brain fails to send the appropriate signal to the breathing muscles to initiate respirations, e.g., as a result of brain stem injury or damage. Mechanical ventilation is the only treatment available to ensure continued breathing. 
     Obstructive sleep apnea (OSA) is far more common. Normally, the muscles of the upper part of the throat keep the airway open to permit air flow into the lungs. When the muscles of the soft palate, the base of the tongue, and the uvula (the small fleshy tissue hanging from the center of the back of the throat) relax and sag, the relaxed tissues may vibrate as air flows past the tissues during breathing, resulting in snoring. Snoring affects about half of men and 25 percent of women—most of whom are age 50 or older. 
     In more serious cases, the airway becomes blocked, making breathing labored, or even stopping it altogether. In a given night, the number of involuntary breathing pauses or “apneic events” may be as high as 20 to 30 or more per hour. These breathing pauses are almost always accompanied by snoring between apnea episodes, although not everyone who snores has the condition. Sleep apnea can also be characterized by choking sensations. 
     Lack of air intake into the lungs results in lower levels of oxygen and increased levels of carbon dioxide in the blood. Upon an apneic event, the sleeping person is unable to continue normal respiratory function and the level of oxygen saturation in the blood is reduced. The brain will sense the condition and cause the sleeper to struggle and gasp for air. Breathing will then resume, often followed by continued apneic events. There are potentially damaging effects to the heart and blood vessels due to abrupt compensatory swings in blood pressure. Upon each event, the sleeping person will be partially aroused from sleep, resulting in a greatly reduced quality of sleep and associated daytime fatigue. The frequent interruptions of deep, restorative sleep often lead to early morning headaches, excessive daytime sleepiness, depression, irritability, and learning and memory difficulties. 
     The medical community has become aware of the increased incidence of heart attacks, hypertension and strokes in people with moderate or severe obstructive sleep apnea. It is estimated that up to 50 percent of sleep apnea patients have high blood pressure. 
     Although some apneic events are normal in all persons and mammals, the frequency of blockages will determine the seriousness of the disease and potential for health damage. When the incidence of blockage is frequent, corrective action should be taken. 
     II. The Anatomy of the Upper Airway 
     As  FIG. 1  shows, the upper airway consists of a conduit that begins at the nasal valve, situated in the tip of the nose, and extends to the larynx, which is also called the voice box because it houses the vocal cords. The pharynx (which, in Greek, means “throat”) is a cone-shaped passageway in the upper airway that leads from the oral and nasal cavities in the head to the esophagus and larynx. The pharynx serves both respiratory and digestive functions. Both circular and longitudinal muscles are present in the walls of this organ, which are called the pharyngeal walls. The circular muscles form constrictions that help push food to the esophagus and prevent air from being swallowed, while the longitudinal muscles lift the walls of the pharynx during swallowing. 
     The pharynx consists of three main divisions. The anterior portion is the nasal pharynx, the back section of the nasal cavity. The nasal pharynx connects to the second region, the oral pharynx, by means of a passage called an isthmus. The oral pharynx begins at the back of the mouth cavity and continues down the throat to the epiglottis, a flap of tissue that covers the air passage to the lungs and that channels food to the esophagus. The isthmus connecting the oral and nasal regions allows humans to breathe through either the nose or the mouth. The third region is the laryngeal pharynx, which begins at the epiglottis and leads down to the esophagus. Its function is to regulate the passage of air to the lungs and food to the esophagus. Air from the nasal cavity flows into the larynx, and food from the oral cavity is routed to the esophagus directly behind the larynx. The epiglottis, a cartilaginous, leaf-shaped flap, functions as a lid to the larynx and, during the act of swallowing, controls the traffic of air and food. 
     The mouth cavity marks the start of the digestive tube. Oval in shape, it consists of two parts: the vestibule and the mouth cavity proper. 
     The vestibule is the smaller outer portion, delimited externally by the lips and cheeks and internally by the gums and teeth. It connects with the body surface through the rima or orifice of the mouth. The vestibule receives the secretion of the parotid salivary glands and connects when the jaws are closed with the mouth cavity proper by an aperture on both sides behind the wisdom teeth, and by narrow clefts between opposing teeth. 
     The mouth cavity proper contains the tongue and is delimited laterally and in the front by the alveolar arches with the teeth therein contained. It receives the secretion from the submaxillary and sublingual salivary glands. The mouth cavity proper connects with the pharynx by a constricted aperture called isthmus faucium. 
     The tongue is a mobile muscular organ that can assume a variety of shapes and positions. The tongue has a relatively fixed inferior part that is attached to the hyoid bone and mandible. The rest of the tongue is called the body of the tongue. It is essentially a mass of muscles that is mostly covered by mucous membrane. The muscles in the tongue do not act in isolation. Some muscles perform multiple actions with parts of one muscle acting independently producing different, sometimes antagonistic, actions. 
     The tongue is partly in the mouth or oral cavity and partly in the pharynx. At rest, it occupies essentially all of the oral cavity. The posterior part of the tongue demarcates the posterior boundary of the oral cavity. Its mucous membrane is thick and freely movable. 
     The tongue is involved with mastication, taste, articulation, and oral cleansing. Its two main functions are forming words during speaking and squeezing food into the pharynx when swallowing. 
     The palate forms the arched roof of the oral or mouth cavity (the mouth) and the floor of the nasal cavities (the nose). It separates the oral cavity from the nasal cavities and the nasal pharynx. The palate consists of two regions—the hard palate anteriorly and the soft palate posteriorly. 
     The hard palate is vaulted and defines the space filled by the tongue when it is at rest. The hard palate has a hard bony skeleton, hence its name. 
     The soft palate has no bony skeleton, hence its name. The soft palate is suspended from the posterior border of the hard palate. It extends posteriorly and inferiorly as a curved free margin from which hangs a conical process, called the uvula. Muscles arise from the base of the cranium and descend into the soft palate. The muscles allow the soft palate to be elevated during swallowing into contact with the posterior pharyngeal wall. The muscles also allow the soft palate to be drawn inferiorly during swallowing into contact with the posterior part of the tongue. 
     The soft palate is thereby very dynamic and movable. When a person swallows, the soft palate initially is tensed to allow the tongue to press against it, to squeeze the bolus of food to the back of the mouth. The soft palate is then elevated posteriorly and superiorly against the pharyngeal wall, acting as a valve which closes and prevents passage of food into the nasal cavity. 
     III. Sleep and the Anatomy of the Upper Airway 
     Although all tissue along this conduit is dynamic and responsive to the respiratory cycle, only the pharynx, in particular the nasopharynx (the area at the soft palate and the pharyngeal walls) and the oropharynx (the area at the tongue base and the pharyngeal walls), is totally collapsible. The pharyngeal structures and individual anatomic components within this region include the pharyngeal walls, the base of the tongue, the soft palate with uvula, and the epiglottis. 
     The cross sectional area of the upper airway varies with the phases of the respiratory cycle. At the initiation of inspiration (Phase I), the airway begins to dilate and then to remain relatively constant through the remainder of inspiration (Phase II). At the onset of expiration (Phase III) the airway begins to dilate, reaching maximum diameter and then diminishing in size so that at the end of expiration (Phase IV), it is at its narrowest, corresponding to the time when the upper airway dilator muscles are least active, and positive intraluminal pressure is lowest. The upper airway, therefore, has the greatest potential for collapse and closure at end-expiration [ref: Schwab R J, Goldberg A N. Upper airway assessment: radiographic and other imaging techniques. Otolaryngol Clin North Am 1998: 31:931-968]. 
     Sleep is characterized by a reduction in upper airway dilator muscle activity. For the individual with obstructive sleep apnea (OSA) and perhaps the other disorders which comprise much of the group of entities called obstructive sleep-disordered breathing (SDB), it is believed that this change in muscle function causes pharyngeal narrowing and collapse. Two possible etiologies for this phenomenon in OSA patients have been theorized. One is that these individuals reduce the airway dilator muscle tone more than non-apneics during sleep (the neural theory). The other is that all individuals experience the same reduction in dilator activity in sleep, but that the apneic has a pharynx that is structurally less stable (the anatomic theory). Both theories may in fact be contributors to OSA, but current studies seem to support that OSA patients have an intrinsically structurally narrowed and more collapsible pharynx [ref: Isono S. Remmers J, Tanaka A Sho Y, Sato J, Nishino T. Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects. J Appl Physiol 1997:82:1319-1326.] Although this phenomenon is often accentuated at specific sites, such as the velopharyngeal level [Isono], studies of closing pressures [Isono] supports dynamic fast MRI imaging that shows narrowing and collapse usually occurs along the entire length of the pharynx [ref: Shellock F G, Schatz C J, Julien P, Silverman J M, Steinberg F, Foo T K F, Hopp M L, Westbrook P R. Occlusion and narrowing of the pharyngeal airway in obstructive sleep apnea: evaluation by ultrafast spoiled GRASS MR imaging. Am J of Roentgenology 1992:158:1019-1024]. 
     IV. Treatment Options 
     To date, the only modality that addresses collapse along the entire upper airway is mechanical positive pressure breathing devices, such as continuous positive airway pressure (CPAP) machines. All other modalities, such as various surgical procedures and oral appliances, by their nature, address specific sectors of the airway (such as palate, tongue base and hyoid levels), but leave portions of pharyngeal wall untreated. This may account for the considerably higher success rate of CPAP over surgery and appliances in controlling OSA. Although CPAP, which in essence acts as an airway splint for the respiratory cycle, is highly successful, it has some very significant shortcomings. It can be cumbersome to wear and travel with, difficult to accept on a social level, and not tolerated by many (for reasons such as claustrophobia, facial and nasal mask pressure sores, airway irritation). These factors have lead to a relatively poor long-term compliance rate. One study has shown that 65% of patients abandon their CPAP treatment in 6 months. 
     Other current treatments for OSA include genioglossal advancement (GA) and maxillomandibular advancement (MMA). These treatments involve highly invasive surgical procedures and a long recovery time, and therefore have relatively low patient appeal. 
     The need remains for simple, cost-effective devices, systems, and methods for reducing or preventing sleep disordered breathing events. 
     SUMMARY OF THE INVENTION 
     The present invention provides systems and methods for resisting posterior movement of both the tongue and the soft palate/uvula during sleep, thereby keeping an airway open. 
     One aspect of the invention provides systems and methods that include a first structure sized and configured for placement in or on a tongue and a second structure sized and configured for placement in or on a region of a soft palate or uvula. The first and second structures each includes a ferromagnetic material. The systems and methods include a third structure sized and configured for placement in or on tissue in a desired relationship anterior of the first and second structures. The third structure includes a magnetic material that magnetically interacts with both the first and second ferromagnetic materials by attracting both the first and second ferromagnetic materials. 
     In one embodiment, the third structure is sized and configured for placement in an oral cavity anterior of the tongue and region of the soft palate or uvula. In this arrangement, the third structure can comprise, e.g., an appliance sized and configured to be fitted on one or more teeth. In this arrangement, the third structure can be selectively released when magnetic interaction with the first and second ferromagnetic materials is not desired and worn when the magnetic interaction is desired. 
     In one embodiment, the third structure is sized and configured for placement in or on tissue outside an oral cavity anterior to the tongue and soft palate. In this arrangement, the third structure can be is sized and configured, e.g., to be worn on a neck and/or a jaw and/or a chin. In this arrangement, the third structure can be selectively released when magnetic interaction with the first and second ferromagnetic materials is not desired and worn when the magnetic interaction is desired. 
     In one embodiment, the first and second ferromagnetic materials comprise magnetized materials. In this arrangement, the systems and methods can further include at least one additional structure. The additional structure is sized and configured for placement in or on a posterior pharyngeal wall across from at least one of the first and second structures. The additional structure includes a magnetic material that magnetically interacts with the magnetized materials of the at least one first and second structures by repelling the magnetized material of the at least one first and second structures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck. 
         FIG. 2  is an anatomical anterior view of the oral cavity, where the tongue has been pulled towards the front to show the roof of the mouth comprising the hard palate (in the front) and the soft palate (in the back). 
         FIG. 3  is an anatomical side view, with sections partly broken away and in section, of a human suffering from one form of sleep apnea involving the soft palate, showing how the tongue base, the soft palate, and the uvula lean against the pharyngeal wall, effectively closing off the airway, resulting in an apneic event. 
         FIGS. 4A to 4D  show in a diagrammatic way representative embodiments of a magnetic force system that resists occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall, with  FIGS. 4A and 4C  showing magnetic interaction of a ferromagnetic structure implanted in regions of a tongue with a magnetic structure carried outside an airway (e.g., on a chin and/or jaw), and with  FIGS. 4B and 4D  showing magnetic interaction of a ferromagnetic structure implanted in regions of a tongue with a magnetic structure carried inside an airway (e.g., in an oral cavity).  FIGS. 4E and 4F  show alternative embodiments of the Tongue System that provide an additional repelling force to resist the collapse of the tongue. 
         FIGS. 5A and 5B  show in a diagrammatic way representative embodiments of a magnetic force system that resists occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a soft palate/uvula against the pharyngeal wall, with  FIG. 5A  showing magnetic interaction of a ferromagnetic structure implanted in a soft palate/uvula with a magnetic structure carried outside an airway (e.g., on a chin and/or jaw), and with  FIG. 5B  showing magnetic interaction of a ferromagnetic structure implanted in a soft palate/uvula with a magnetic structure carried inside an airway (e.g., in an oral cavity).  FIGS. 5C and 5D  show alternative embodiments of the Soft Palate System that provide an additional repelling force to resist the collapse of the soft palate/uvula. 
         FIGS. 6A and 6B  show in a diagrammatic way representative embodiments of a magnetic force system that resists occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of both a tongue and a soft palate/uvula against the pharyngeal wall, with  FIG. 6A  showing magnetic interaction of ferromagnetic structures implanted in a tongue and a soft palate/uvula with a magnetic structure carried outside an airway (e.g., on a chin and/or jaw), and with  FIG. 6B  showing magnetic interaction of ferromagnetic structures implanted in a tongue and a soft palate/uvula with a magnetic structure carried inside an airway (e.g., in an oral cavity).  FIGS. 6C and 6D  show alternative embodiments of the Combined System that provide an additional repelling force to resist the collapse of the tongue and soft palate/uvula. 
         FIGS. 7A to 7C  show representative embodiments of magnetic structures sized and configured to be worn on a jaw and/or a chin outside an airway to magnetically interact with one or more magnetic structures carried within an airway, e.g., in or on a tongue and/or soft palate/uvula in the manner shown in  FIGS. 4A ,  4 C,  5 A, and  6 A. 
         FIGS. 8A and 8B  show representative embodiments of magnetic structures sized and configured to be worn about a neck outside an airway to magnetically interact with one or more ferromagnetic structures carried within an airway, e.g., in or on a tongue and/or soft palate/uvula in the manner shown in  FIGS. 4A ,  4 C,  5 A, and  6 A. 
         FIGS. 9A to 9E  show representative embodiments of a magnetic structures sized and configured to be worn within an airway, e.g., on teeth within an oral cavity, to magnetically interact with ferromagnetic structures carried within an airway, e.g., in or on a tongue and/or soft palate/uvula in the manner shown in  FIGS. 4B ,  4 D,  5 B, and  6 B. 
         FIG. 10  is a perspective view of a ferromagnetic material sized and configured for implantation as part of a magnetic force system shown in  FIGS. 4A to 4D , or  5 A or  5 B, or  6 A or  6 B. 
         FIG. 11  is a perspective view of an array of ferromagnetic materials in a carrier that is sized and configured for implantation as part of the magnetic force system shown in  FIGS. 4A to 4D , or  5 A or  5 B, or  6 A or  6 B. 
         FIG. 12A  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIGS. 4A  or  4 C comprising a ferromagnetic structure implanted in a region of a tongue that interacts with a magnetic structure carried outside an airway (e.g., on a chin and/or jaw), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 12B  is a perspective view of a ferromagnetic structure sized and configured to be implanted in a region of a tongue and forming a part of the system shown in  FIG. 12A . 
         FIGS. 12C and 12D  are, respectively, a perspective view and a side view of a magnetic structure sized and configured to be worn outside an airway (e.g., on a chin and/or jaw) and forming a part of the system shown in  FIG. 12A . 
         FIG. 12E  is an anatomical anterior view of the oral cavity, showing the tongue and the hard and soft palates, and further showing the magnetic force system as shown in  FIG. 12A , in which the ferromagnetic structure in the tongue extends generally symmetrically across the centerline of the tongue and the magnetic structure worn on the chin and/or jaw includes magnets on both lateral sides of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 12F  is an anatomical anterior view of the oral cavity, showing the tongue and the hard and soft palates, and further showing the magnetic force system as shown in  FIG. 12A , in which the ferromagnetic structure in the tongue extends generally symmetrically across the centerline of the tongue and the magnetic structure worn on the chin and/or jaw includes magnets only on one lateral side of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 12G  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIGS. 4B  or  4 D comprising a ferromagnetic structure implanted in a region of a tongue that interacts with a magnetic structure carried inside an airway (e.g., within an oral cavity), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 12H  is an anatomical anterior view of the oral cavity, showing the tongue and the hard and soft palates, and further showing the magnetic force system as shown in  FIG. 12G , in which the ferromagnetic structure in the tongue extends generally symmetrically across the centerline of the tongue and the magnetic structure worn within the oral cavity includes magnets on both lateral sides of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 13A  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIGS. 4B  or  4 D comprising a ferromagnetic structure implanted in a region of a tongue that interacts with a magnetic structure carried inside an airway (e.g., in an oral cavity), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 13B  is a perspective view of a ferromagnetic structure sized and configured to be implanted in a region of a tongue and forming a part of the system shown in  FIG. 13A . 
         FIGS. 13C  is a perspective view of a magnetic structure sized and configured to be worn within an airway, e.g., on teeth within an oral cavity, and forming a part of the system shown in  FIG. 13A . 
         FIG. 13D  is an anatomical anterior view of the oral cavity, showing the tongue and the hard and soft palates, and further showing the magnetic force system as shown in  FIG. 13A , in which the ferromagnetic structure in the tongue extends generally symmetrically across the centerline of the tongue and the magnetic structure worn on teeth within an oral cavity includes magnets on both lateral sides of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in FIG.  3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 14A  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 6B  comprising ferromagnetic structures implanted in a region of a tongue and soft palate/uvula that interact with a magnetic structure carried inside an airway (e.g., in an oral cavity), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue and soft palate/uvula against the pharyngeal wall. 
         FIG. 14B  is a perspective view of a ferromagnetic structure sized and configured to be implanted in a region of a tongue and a soft palate/uvula, and forming a part of the system shown in  FIG. 14A . 
         FIGS. 14C  is a perspective view of a magnetic structure sized and configured to be worn within an airway, e.g., on teeth within an oral cavity, and forming a part of the system shown in  FIG. 14A . 
         FIG. 14D  is an anatomical anterior view of the oral cavity, showing the tongue and the hard and soft palates, and further showing the magnetic force system as shown in  FIG. 14A , in which the ferromagnetic structures in the tongue and soft palate/uvula extend generally symmetrically across the centerline of the tongue and soft palate and the magnetic structure worn on teeth within an oral cavity includes magnets on both lateral sides of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 15  is a graph showing how magnetic force is sensitive to distance (curve SM) and how titration of a magnetic force field (curve MM) can reduce with sensitivity of the force-distance relationship with a prescribed working space defined during normal anatomic functions of a tongue and soft palate/uvula. 
         FIGS. 16A and 17A  are diagrammatic views of a titrated magnetic structure carried on a chin or jaw outside an airway or on teeth in an airway that interacts with a ferromagnetic structure implanted in a tongue or a soft palate/uvula, also showing in this arrangement how the magnetic attracting forces have been moderated by the titration to the sensitivity of the force-distance relationship with a prescribed working space defined during normal anatomic functions of a tongue and soft palate/uvula. 
         FIGS. 16B and 17B  are diagrammatic views of a titrated magnetic structure worn about a neck outside an airway that interacts with a ferromagnetic structure implanted in a tongue or a soft palate/uvula, also showing in this arrangement how the magnetic attracting forces that have been moderated by the titration to the sensitivity of the force-distance relationship with a prescribed working space defined during normal anatomic functions of a tongue and soft palate/uvula. 
         FIGS. 18A and 18B  are diagrammatic representations of a finite element analysis showing the flux lines for the titrated magnetic structures of the type shown in FIGS.  16 A/ 16 B and  17 A/ 17 B, demonstrating how the magnetic attracting forces have been moderated by titration to the sensitivity of the force-distance relationship with a prescribed working space defined during normal anatomic functions of a tongue and soft palate/uvula. 
         FIG. 19  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 4A  in which a ferromagnetic structure implanted in a region of a tongue includes mobile ferromagnetic material that interacts with a magnetic structure carried outside an airway (e.g., on a chin and/or jaw), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue and soft palate/uvula against the pharyngeal wall. 
         FIGS. 20A and 20B  are anatomic side section views of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 4B  in which a ferromagnetic structure implanted in a region of a tongue includes mobile ferromagnetic material that interacts with a magnetic structure carried inside an airway (e.g., on teeth within an oral cavity), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue and soft palate/uvula against the pharyngeal wall. 
         FIG. 21A  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 4A  in which a ferromagnetic structure implanted in a region of a tongue interacts with a magnetic structure that includes mobile magnetic material carried outside an airway (e.g., on a chin and/or jaw), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue and soft palate/uvula against the pharyngeal wall. 
         FIGS. 21B to 21F  are perspective views of representative embodiments of a magnetic structure sized and configured to be worn within an airway, e.g., on teeth within an oral cavity, that includes mobile magnetic material, forming a part of the system shown in  FIG. 21A . 
         FIG. 22A  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 5B , in which a ferromagnetic structure implanted in a region of a soft palate/uvula interacts with a magnetic structure that includes mobile magnetic material carried inside an airway (e.g., on teeth within an oral cavity), to resist the occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue and soft palate/uvula against the pharyngeal wall. 
         FIGS. 22B and 22C  are perspective views of representative embodiments of a magnetic structure sized and configured to be worn within an airway, e.g., on teeth within an oral cavity, that includes mobile magnetic material, forming a part of the system shown in  FIG. 22A . 
         FIG. 23A  is an anatomic side section view of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 4A  in which a ferromagnetic structure implanted in a region of a tongue includes mobile ferromagnetic material that interacts with a magnetic structure carried outside an airway (e.g., on a chin and/or jaw), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue and soft palate/uvula against the pharyngeal wall. 
         FIGS. 23B and 23C  are perspective views of representative embodiments of a magnetic structure sized and configured to be implanted in a region of a tongue that includes mobile magnetic material, forming a part of the system shown in  FIG. 23A . 
         FIGS. 24A ,  24 B, and  24 C are representative diagrammatic embodiments of mobile ferromagnetic materials of various shapes and forms that can form a part of the systems shown in  FIG. 19 ;  FIGS. 20A and 20B ;  FIGS. 21A to 21F ;  FIGS. 22A to 22C ; or  FIGS. 23A to 23C . 
         FIG. 25  is an anatomical superior view of the oral cavity, showing the tongue and pharyngeal conduit, and further showing a ferromagnetic structure implanted in a tongue, in which the ferromagnetic structure extends generally asymmetrically only on one lateral side of the tongue, the view also showing a tissue condition as shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 26A  is an anatomical superior view of the oral cavity, like that shown in  FIG. 25 , in which the ferromagnetic structure implanted asymmetrically in the tongue interacts with a magnetic structure inside an airway (e.g., on teeth within an oral cavity) having magnets on both lateral sides of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 26B  is an anatomical superior view of the oral cavity, like that shown in  FIG. 25 , in which the ferromagnetic structure implanted asymmetrically in the tongue interacts with a magnetic structure inside an airway (e.g., on teeth within an oral cavity) having magnets only on one lateral side of the oral cavity opposite to the asymmetric ferromagnetic structure in the tongue, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 27  is an anatomical superior view of the oral cavity, like that shown in  FIG. 25 , in which the ferromagnetic structure implanted asymmetrically in the tongue interacts with a magnetic structure implanted in a pharyngeal wall opposite to the ferromagnetic structure, and further showing in this arrangement the magnetic repelling forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 28  is an anatomical superior view of the oral cavity, showing the tongue and pharyngeal conduit, and further showing a ferromagnetic structure implanted in a tongue, in which the ferromagnetic structure extends generally asymmetrically only on one lateral side of the tongue, but includes an appendage that is free of a ferromagnetic material extending into the opposite lateral side of the tongue, the view also showing a tissue condition as shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 29A  is an anatomical superior view of the oral cavity, like that shown in  FIG. 28 , in which the ferromagnetic structure implanted asymmetrically in the tongue with a non-ferromagnetic appendage interacts with a magnetic structure inside an airway (e.g., on teeth within an oral cavity) having magnets on both lateral sides of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 29B  is an anatomical superior view of the oral cavity, like that shown in  FIG. 28 , in which the ferromagnetic structure implanted asymmetrically in the tongue with a non-ferromagnetic appendage interacts with a magnetic structure inside an airway (e.g., on teeth within an oral cavity) having magnets only on one lateral side of the oral cavity opposite to the asymmetric ferromagnetic structure in the tongue, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 30  is an anatomical superior view of the oral cavity, like that shown in  FIG. 28 , in which the ferromagnetic structure implanted asymmetrically in the tongue with a non-ferromagnetic appendage interacts with a magnetic structure implanted in a pharyngeal wall opposite to the ferromagnetic structure, and further showing in this arrangement the magnetic repelling forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIGS. 31A and 31B  are, respectively, a perspective view and a top view of a representative embodiment of an asymmetric ferromagnetic structure having a non-ferromagnetic appendage that includes a non-ferromagnetic rudder-type structure to further stabilize the structure and move more tissue in response to magnetic interaction of a magnetic structure wither inside or outside the airway, or both. 
         FIG. 31C  is an anatomical superior view of the oral cavity, showing the tongue and pharyngeal conduit, and further showing the ferromagnetic structure shown in  FIGS. 31A and 31B  implanted in a tongue, the view also showing a tissue condition as shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 31D  is an anatomical superior view of the oral cavity, like that shown in  FIG. 31C , in which the ferromagnetic structure shown in  FIG. 31C  interacts with a magnetic structure inside an airway (e.g., on teeth within an oral cavity) having magnets only on one lateral side of the oral cavity opposite to the asymmetric ferromagnetic structure in the tongue, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIGS. 32A and 32B  are, respectively, a perspective view and a top view of a representative embodiment of a magnetic structure having opposite arm regions of opposite magnetic polarity and an intermediate non-magnetic rudder-type structure to further stabilize the structure and move more tissue in response to magnetic interaction of a magnetic structure wither inside or outside the airway, or both. 
         FIG. 33  is an anatomical superior view of the oral cavity, showing the tongue and pharyngeal conduit, and further showing the ferromagnetic structure shown in  FIGS. 32A and 32B  implanted in a tongue, the view also showing a tissue condition as shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIGS. 34A and 34B  are anatomical superior views of the oral cavity, like that shown in  FIG. 33 , in which the ferromagnetic structure shown in  FIG. 33  interacts with a magnetic structure inside an airway (e.g., on teeth within an oral cavity) having magnets only on one lateral side of the oral cavity, and further showing in this arrangement the magnetic attracting forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 35  is an anatomical superior view of the oral cavity, like that shown in  FIG. 33 , in which the ferromagnetic structure shown in  FIGS. 33  interacts with a magnetic structure implanted in a pharyngeal wall opposite to the ferromagnetic structure, and further showing in this arrangement the magnetic attracting and repelling forces that resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall. 
         FIG. 36  is an anatomic sagittal view of the tongue, soft palate/uvula, and pharyngeal wall, showing the resolution of forces F-sep and F-nat to provide an optimal therapeutic force F-mag that, at night, resists collapse of the tongue against the pharyngeal wall during sleep, yet does not affect speech, swallowing or drinking during normal activities awake or asleep. 
         FIG. 37  is an anatomic sagittal view of the tongue, soft palate/uvula, and pharyngeal wall, showing the resolution of forces F-sep and F-nat to provide an optimal therapeutic force F-mag that, at night, resists collapse of the soft palate/uvula against the pharyngeal wall during sleep, yet does not affect speech, swallowing or drinking during normal activities awake or asleep. 
         FIG. 38  is a chart executing an implant force scaling strategy. 
         FIGS. 39A and 39B  are anatomic side section views of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing a representative magnetic force system of a type shown in  FIG. 4C  comprising a ferromagnetic structure implanted in a lower, inferior region of a tongue that interacts with a magnetic structure carried outside an airway (e.g., on a jaw), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall, the ferromagnetic structure including (in  FIG. 39A ) a single tethered anchoring assembly and (in  FIG. 39B ) a multiple tether anchoring assembly to stabilize the ferromagnetic structure in close proximity to the external jaw-mounted magnetic structure. 
         FIGS. 39C and 39D  are anatomic side section views of the upper airway of a human, showing the nasal and oral cavities, tongue, hard palate, soft palate, oral pharynx, chin and neck, and further showing another representative tethered magnetic force system of a type shown in  FIGS. 40A and 40B , comprising a ferromagnetic structure implanted in a more anterior region of a tongue that interacts with a magnetic structure carried outside an airway (e.g., on a chin), to resist occurrence of the tissue condition shown in  FIG. 3 , involving the collapse of a tongue against the pharyngeal wall, the ferromagnetic structure including (in  FIG. 39C ) a single tethered anchoring assembly and (in  FIG. 39D ) a multiple tether anchoring assembly to stabilize the ferromagnetic structure in close proximity to the external chin-mounted magnetic structure. 
         FIG. 39E  is a perspective view of a representative tether anchoring assembly that includes an umbrella-like anchor that collapses for implantation and expands in situ within the implantation site. 
         FIG. 39F  is a perspective view of a representative tether anchoring assembly that is adjustable and lockable to adjust and control tension. 
         FIGS. 40A to 40C  show representative embodiments of a ferromagnetic structure implanted in an anterior or caudal anterior region of a tongue, or in the myohyoid muscle, in proximity to external magnetic structures, e.g., a mouthpiece carried within the oral cavity or an external carrier placed on or under the chin or about the neck. 
         FIGS. 41A and 41B  show devices that consist of one or more ferromagnetic structure(s) attached to one or more elastic components sized and configured to deflect under load in a prescribed manner and to recover an initial shape when unloaded. 
     
    
    
     DETAILED DESCRIPTION 
     This Specification discloses various magnetic implants and external devices, systems, and methods for the use of attracting magnetic force to maintain a patent airway. For example, the various aspects of the invention have application in procedures requiring the restriction of tissue collapse in and/or around the body, such as a passageway within the body. The devices, systems, and methods that embody features of the invention are also adaptable for use with devices, systems, and methods that are not restricted to tissue based applications. 
     The devices, systems, and methods are particularly well suited for treating sleep disordered breathing, including sleep apnea. For this reason, the devices, systems, and methods will be described in this context. Still, it should be appreciated that the disclosed devices, systems, and methods are applicable for use in treating other dysfunctions elsewhere in the body, which are not necessarily sleep disorder related. 
     I. The Tongue and the Soft Palate 
     A. Anatomy 
       FIG. 2  shows an anatomical view of the oral cavity, where the tongue has been pulled towards the front.  FIG. 2  shows the tongue and the roof of the mouth, i.e., the palate, as previously described and as also shown in  FIG. 1 .  FIG. 2  shows the two parts of the palate which have also been previously described: namely, the hard palate (in the front) and the soft palate (in the back). 
     The hard palate is bounded in the front and laterally by the alveolar arches and gums and in the back by the soft palate. A dense structure made up by the periosteum and the mucous membrane of the mouth covers the hard palate. The linear raphé lies along the middle line of the hard palate. 
     The soft palate is a movable fold, suspended from the posterior border of the hard palate and forms an incomplete dividing line (septum) between the mouth and the pharynx. The soft palate comprises a mucous membrane that envelops muscular fibers, an aponeurosis, vessels, nerves, adenoid tissue, and mucous glands. 
     When the soft palate is relaxed and hanging, the anterior surface is concave and follows the same line as the roof of the mouth. The posterior surface of the soft palate is convex and is a continuance of the mucous membrane that covers the bottom part of the nasal cavities. The upper boundary of the soft palate attaches to the hard palate; the sides become part of the pharynx; and the lower boundary is free. The lower boundary which hangs down, separating the mouth and the pharynx is known as the palatine velum. In the middle of the lower boundary, the small, fleshy cone-shaped protuberance is called the uvula. The arches are located laterally and downwardly from the uvula. These arches are called the glossopalatine arch (the anterior arch) and the pharyngopalatine arch (the posterior arch). The palatine aponeurosis is a thin, firm fiber-filled lamella which gives support to the muscles and makes the soft palate strong. 
     The tongue is located over the floor of the oral cavity. In human beings the tongue is an organ that undergoes a wide variety of movements, partly because it is involved in a broad range of activities, including speech, eating and swallowing. When a human is awake, the tongue normally moves in an up and forward position. When a human is asleep, the muscles of the tongue relax and the tongue is able to move in an even broader range of directions. This movement can occur laterally, posteriorly, anteriorly, cranially, caudally, in a rolling manner, or any combinations thereof. 
     During the process of eating and swallowing, the uvula prevents the food from entering the nasopharynx and the muscles of the soft palate push the food down into the pharynx. The tongue can move in conjunction with other structures (i.e. with the tongue and pharyngeal wall coming together, or with the tongue and palate coming together) or independently of other structures (i.e. tongue movement without palate, pharyngeal wall, or epiglottis movement). 
     B. The Tongue/Soft Palate and Sleep Apnea 
     Sleep apnea occurs when the airway becomes obstructed; hypopnea occurs when the airway is partially obstructed. Sleep apnea takes many forms; closure of the airway can occur at any number of anatomical structures along the airway, including any combination of the tongue, soft palate, epiglottis, and pharyngeal wall. For example, the tongue may collapse with respect to the pharyngeal wall, or both the base of the tongue and the pharyngeal wall may collapse at the same time. Likewise, the soft palate/uvula may collapse with respect to the pharyngeal wall and/or tongue, or both the soft palate/uvula and/or tongue and/or the pharyngeal wall may collapse at the same time. Thus, sleep apnea may be treated by either preventing the collapse of the tongue, pharyngeal wall, soft palate/uvula independently, and/or one or more of the tongue base, the pharyngeal wall, and/or the soft palate/uvula at the same time. 
       FIG. 1  is an anatomical side view of the upper airway system in a normal patient, showing the nasal and oral cavities, tongue, hard palate, soft palate, oropharynx, chin and neck.  FIG. 3  shows an anatomical side view of a patient suffering from one form of sleep apnea involving at the same time the tongue, the pharyngeal wall, and the soft palate/uvula. As shown in  FIG. 3 , the tongue base, the soft palate, and the uvula lean against the pharyngeal wall, effectively closing off the airway. An apneic episode can occur as a result. 
     II. Attracting Magnetic Force Systems 
     A. Overview 
     1. Resisting Collapse of the Tongue (The Tongue System) 
       FIGS. 4A to 4D  show in a diagrammatic way representative embodiments of a magnetic force system  10   a  that resists, at least in part, the tissue condition shown in  FIG. 3 , involving the collapse of the tongue against the pharyngeal wall. This system  10   a  in its various embodiments will be in shorthand called the Tongue System. The Tongue System  10   a  includes one magnetic structure  12  and one magnetic structure  14  to create an attracting magnetic force between the two structures, which maintains the tongue in a position spaced away from the posterior pharyngeal wall, as  FIGS. 4A ,  4 B,  4 C, and  4 D show. The magnetic force field resists posterior movement of the tongue during sleep, keeping the airway open. An apneic episode is avoided. 
     In the representative embodiments shown in  FIGS. 4A and 4B , the magnetic structure  12  is positioned in or on the tongue. More specifically, magnetic structure  12  can be positioned either in the anterior or in the posterior region of the tongue. In  FIG. 4A , the magnetic structure  14 , which the magnetic structure  12  interacts with, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 4B , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). 
     In the representative embodiments shown in  FIGS. 4C and 4D , the magnetic structure  12  is positioned in the general area between the mandible and the hyoid bone, either in or on the hyoid muscles (e.g. one or more of the suprahyoid muscles such as the mylohyoid muscles, the geniohyoid muscles, or the stylohyoid muscles, or the digastric muscles), or under the skin. In  FIG. 4C , the magnetic structure  14 , which the magnetic structure  12  interacts with, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 4D , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). 
     2. Resisting Collapse of the Soft Palate (The Soft Palate System) 
       FIGS. 5A and 5B  show in a diagrammatic way representative embodiments of a magnetic force system  10   b  that resists, at least in part, the tissue condition shown in  FIG. 3 , involving the collapse of the soft palate/uvula against the pharyngeal wall. This system  10   b  in its various embodiments will be in shorthand called the Soft Palate System. The Soft Palate System  10   b  includes one magnetic structure  12  and one magnetic structure  14  to create a magnetic force field, which maintains the soft palate/uvula in a position spaced away from the posterior pharyngeal wall, as  FIGS. 5A and 5B  show. The magnetic force field resists posterior movement of the soft palate/uvula during sleep, keeping the airway open. An apneic episode is avoided. 
     In the representative embodiments shown in  FIGS. 5A and 5B , the magnetic structure  12  is positioned in or on the soft palate/uvula. In  FIG. 5A , the magnetic structure  14 , which the magnetic structure  12  interacts with, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 5B , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). 
     3. Resisting Collapse of the Tongue and the Soft Palate (The Combined System) 
       FIGS. 6A and 6B  show in a diagrammatic way representative embodiments of a magnetic force system  10   c  that resists, at least in part, the tissue condition shown in  FIG. 3 , involving the collapse of both the tongue and the soft palate/uvula against the pharyngeal wall. This system  10   c  in its various embodiments will be in shorthand called the Combined System. The Combined System  10   c  includes two magnetic structures  12   a  and  12   b  and one magnetic structure  14  to create a magnetic force between the two, which maintains both the tongue and the soft palate/uvula in a position spaced away from the posterior pharyngeal wall, as  FIGS. 6A and 6B  show. The magnetic force field resists posterior movement of both the tongue and the soft palate/uvula during sleep, keeping the airway open. An apneic episode is avoided. 
     In the representative embodiments shown in  FIGS. 6A and 6B , the magnetic structure  12   a  is positioned in or on the soft palate/uvula and the magnetic structure  12   b  is positioned in or on the posterior (back) of the tongue. In  FIG. 6A , the magnetic structure  14 , which the magnetic structures  12   a  and  12   b  interact with, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 6B , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). It should be appreciated that the magnetic structure  12   b  can, alternatively, be positioned in the general area between the mandible and the hyoid bone, either in or on the muscles (e.g. mylohyoid, geniohyoid, or digastric), or under the skin, in the manner shown in phantom lines in  FIGS. 6A and 6B , in the manner previously shown in  FIGS. 4C and 4D ). 
     B. Placement of the Ferromagnetic Structures 
     The magnetic force systems  10   a ,  10   b , and  10   c  can be variously constructed. In the illustrated arrangements, all the force systems  10   a ,  10   b , and  10   c  include in their most basic form the two structures  12  and  14 . One structure  12  is placed in or on tissue that is relatively mobile and subject to collapse, if not restrained from doing so. The other structure  14  is placed in or on tissue that is, relatively speaking, immobile, relative to the direction of collapse. 
     The structures  12  and  14  comprise ferromagnetic materials. The ferromagnetic materials of the structures  12  and  14  are sized, selected, and arranged to magnetically interact by developing between the structures  12  and  14  a magnetic force. The magnetic force includes at least one vector or component that magnetically attracts the structure  12  in or on the mobile tissue toward the structure  14  in or on the relatively immobile tissue. Posterior movement or other movement which could lead to an apneic or hypopneic obstruction or narrowing of the relatively mobile tissue is thereby resisted. 
     1. The First Structure 
     The first structure  12  is internally placed in or on the relatively mobile tissue in the airway targeted for treatment. In the Tongue System  10   a  ( FIGS. 4A to 4D ), the targeted tissue is tongue tissue, and, in particular, tissue at or near the posterior part (base) of the tongue across from the pharyngeal wall ( FIGS. 4A and 4B ) or in the general area between the mandible and the hyoid bone, either in or on the muscles (e.g. mylohyoid, geniohyoid, or digastric), or under the skin ( FIGS. 4C and 4D ). In the Soft Palate System  10   b  ( FIGS. 5A and 5B ) the targeted tissue is the soft palate/uvula across the airway from the pharyngeal wall. In the Combined System  10   c  ( FIGS. 6A and 6B ), the targeted tissue is both tongue tissue (or, alternatively, in the general area between the mandible and the hyoid bone, either in or on the muscles (e.g. mylohyoid, geniohyoid, or digastric), or under the skin) and the soft palate/uvula across the airway from the pharyngeal wall. 
     Due to its interior placement, the ferromagnetic structure  12  is desirably sized and configured for relatively long-term placement or implantation in tissue. 
     2. The Second Structure 
     As previously described, the second structure  14  can be placed either externally in or on relatively immobile tissue outside the airway or internally in or on relatively immobile tissue within an airway. The structure  14  is placed to magnetically interact with the structure  12  by developing between the ferromagnetic materials on the structures  12  and  14  a magnetic force that includes at least one vector or component that magnetically attracts the structure  12  in or on the mobile tissue toward the structure  14  in or on the relatively less mobile tissue. 
     In the Tongue System  10   a  ( FIGS. 4A to 4D ), the magnetic attracting force between the two ferromagnetic structures  12  and  14  resists posterior or other movement of the tongue toward the posterior pharyngeal wall. In the Soft Palate System  10   b  ( FIGS. 5A and 5B ), the magnetic attracting force between the two ferromagnetic structures  12  and the one ferromagnetic structure  14  resists posterior or other movement of the soft palate/uvula toward the posterior pharyngeal wall. In the Combined System  10   c  ( FIGS. 6A and 6B ), the magnetic attracting force between the two ferromagnetic structures  12  and ferromagnetic structure  14  resists posterior movement of both the tongue and the soft palate/uvula toward the posterior pharyngeal wall. In all systems  10   a ,  10   b , and  10   c , the magnetic force prevents, in whole or in part, the occurrence of the airway-occluding tissue condition shown in  FIG. 3 . As  FIGS. 4A to 4D ,  5 A and  5 B, and  6 A and  6 B show, the magnetic force between the first and second ferromagnetic structures  12  and ferromagnetic structure  14  works to keep the airway open (i.e., patent) during sleep. 
     Due to its placement, the ferromagnetic structure  14  is desirably sized and configured to be removable, so that it can be temporarily placed into association with the more permanent ferromagnetic structure  12  and thereafter removed, when desired, from the association. Thus, the ferromagnetic structure  14  can be placed into association with the internal ferromagnetic structure  12  when the presence of the magnetic force field is desired, e.g., during sleep, and can be removed at other times. A removable structure  14  also has the advantage of being easily and accurately titrated (i.e. increasing or decreasing the force to optimize the performance of the system). This titration could be accomplished by switching different ferromagnetic materials of various strengths by a clinician or by the user and/or by adjusting the relative position or distance of the removable structure  14  with respect to the internal structure  12 . 
     a. External Placement 
     In  FIGS. 4A ,  4 C,  5 A, and  6 A, the second structure  14  is shown placed on relatively immobile tissue externally outside the airway. More particularly, in  FIGS. 4A ,  4 C,  5 A, and  6 A, the second structure  14  is shown placed externally on or under the chin or lower jaw. Various ways of placing the structure  14  in this position are possible. 
     For example, as shown in  FIG. 7A , the external ferromagnetic structure  14  can be shaped, sized and configured as a carrier  28  that can be secured at the level of the mandibular joint by, e.g., headgear that includes a strap  32  that fits over the head. As will be described in greater detail later, the carrier  28  includes an array of one or more ferromagnetic materials  26  positioned and arranged to attract the ferromagnetic materials in the internal structure  12  positioned in or on the tongue, the soft palate/uvula, or both. 
     Alternatively, as  FIG. 7B  shows, the carrier  28  of the external ferromagnetic structure  14  can be shaped to include a cup  34  that fits over the chin, to add further stability and comfort. In this arrangement, the headgear strap  32  attaches to the carrier  28  at the level of the mandibular joint, as well as to the chin cup  34 , helping to immobilize the position of the headgear. 
     As  FIG. 7C  shows, the carrier  28  can be shaped, sized, and configured as a chin cup  34  that includes an extension, which extends a measured minimum distance (e.g., at least 4 cm) under the chin below the tongue. In this arrangement, the extension carries at least one ferromagnetic material  26 , which interacts with the ferromagnetic materials in the internal structure  12  positioned in or on the tongue. In this embodiment the headgear strap  32  can fit over the head and attach to both the chin cup and its extension under the chin. This embodiment is particularly useful when the therapeutic objective is to principally target resistance to posterior movement of the tongue. 
     In an alternative arrangement, the second structure  14  can be placed around the neck. As shown in  FIG. 8A , the second structure  14  comprises a carrier  28  that includes an array of one or more ferromagnetic materials  26 . The carrier  28  includes a neck collar  38 , which serves to position and orient the ferromagnetic materials  18  to attract the ferromagnetic materials in the internal structure  12  positioned in or on the tongue, the soft palate/uvula, or both. 
     In the embodiment shown in  FIG. 8B , an anterior part of the neck collar that fits under the chin is higher than the posterior part that fits under the back of the head. This configuration raises the level of the chin and serves to extend the neck, by tilting the head back and raising the chin. The embodiment shown in  FIG. 8B  mimics the extension of the neck accomplished during CPR. The extension may add a mechanical enhancement to the magnetic force field, helping to maintain or further open up the airway. 
     Benefits of using external magnetic devices include: (1) larger and stronger magnets may be used than could be either implanted or affixed to an appliance worn in the mouth (as will be described in greater detail later); (2) external devices are easily removed, so that the force delivered need only be experienced when the patient wishes to sleep, and not during eating or speech thus minimizing the effect of magnetic force on these activities; and (3) without need for surgical intervention, the amount and direction of the magnetic forces can be changed. This is accomplished by exchanging magnet types and sizes and by changing the location of the magnets within the external device. 
     b. Internal Placement 
     Alternatively, the second structure  14  can be placed in or on relatively immobile tissue internally inside the airway, e.g., within an oral cavity in proximity to the first structure  12  (which is desirably placed in or on a tongue and/or soft palate/uvula). For example (as  FIGS. 9A ,  9 B,  9 C,  9 D, and  9 E show), the second structure  14  can be shaped, sized and configured to be fitted inside the mouth in various positions along the inner or outer edge of the lower teeth or covering the top of the lower or upper teeth, the second structure also comprising magnetic materials that are generally aligned with, on top of, or below the tongue. The structure could, in principle, also be placed on the upper teeth. 
     For example, in  FIG. 9A , the second ferromagnetic structure  14  comprises a carrier  28  that takes the form of a mouthpiece  40  that fits along the inside edge of the lower teeth. An array of one or more ferromagnetic materials  26  is carried by the carrier  28 , as will be described in greater detail later. In the illustrated embodiment, the mouthpiece  40  attaches to the lower teeth in a suitable manner, e.g., with the hooks  42  as shown. 
       FIG. 9B  shows an alternative arrangement. In this arrangement, the second ferromagnetic structure  14  comprises a carrier  28  that takes the form of a mouthpiece  40  that fits along the outside edge of the lower teeth in a suitable manner, e.g., the two hooks  42  as shown. An array of one or more ferromagnetic materials  26  is carried by the carrier  28 , as will be described in greater detail later. 
       FIG. 9C  shows another alternative arrangement. In this arrangement, the second ferromagnetic structure  14  comprises a carrier  28  that takes the form of a mouthpiece  40  that is pre-formed by molding to fit and cover the lower teeth. An array of one or more ferromagnetic materials  26  is carried by the carrier  28 , as will be described in greater detail later. 
       FIGS. 9D and 9E  are other alternative embodiments of the mouthpiece  40  of the type shown in  FIG. 9C , which fit over the lower teeth. In  FIGS. 9D and 9E , the mouthpiece  40  includes one or more protrusions  43  that extend medially from the teeth into the oral cavity. In  FIG. 9D , the one or more protrusions extend over the tongue. In  FIG. 9E , the one or more protrusions  43 ′ extend beneath the tongue. The protrusions carry an array of one or more ferromagnetic materials  26 . In this way, the ferromagnetic materials  26  can be placed in close superior alignment ( FIG. 9D ) or inferior alignment ( FIG. 9E ) with the ferromagnetic materials  26  in the first structure  12  in the tongue, and/or in close inferior alignment with the ferromagnetic materials  26  in the first structure  12  in the soft palate/uvula. 
     Alternative embodiments to the mouthpieces  40  shown in  FIGS. 9A to 9D  are also envisioned where the carrier  28  fits over the upper teeth. 
     The configuration and placement of the various mouthpieces  40  in  FIGS. 9A ,  9 B,  9 C,  9 D, and  9 E physically locate the ferromagnetic materials  26  of the second ferromagnetic structure  14  in relatively close proximity to a ferromagnetic structure  12  placed in or on the tongue and/or soft palate/uvula. The proximity increases the magnitude of the magnetic field within the airway necessary to achieve the desired therapeutic effect. Thus, the proximity makes possible the use of relatively smaller ferromagnetic materials in both structures  12  and  14 , when compared to an external second magnetic structure in a collar, head gear or other location. 
     C. Configuration of the Ferromagnetic Structures 
     As seen in  FIG. 10 , in its most basic form, the magnetic structures  12  and  14  of the magnetic force system  10  each comprises at least one ferromagnetic material. The ferromagnetic material(s) of the magnetic structure  12  will be identified by reference number  16 , the ferromagnetic material(s) for the magnetic structure  14  will be identified by reference number  18 . The ferromagnetic materials  16  of the first structure  12  are placed in or on the targeted tissue regions (tongue and/or soft palate/uvula). The ferromagnetic materials  18  of the second structure  14  are placed under the chin, the lower jaw, along the inner or outer edge of the lower teeth, or on top of the lower teeth, along the inner or outer edge of the upper teeth, or beneath the upper teeth. The ferromagnetic materials  16  and  18  of the magnetic structures  12  and  14 , forming the force systems  10   a ,  10   b , and  10   c  are placed to magnetically interact and stabilize the tongue and/or soft palate/uvula, thereby resisting the collapse of tissue in the airway between the tongue and/or soft palate/uvula and the pharyngeal wall during sleep. 
     1. Orientation of Magnetic Poles 
     Each ferromagnetic material  16  and  18  can comprise a permanent magnet. A permanent magnet is characterized as a material showing resistance to external demagnetizing forces once being magnetized. That is, a high external magnetic field is required in order to remove the residual magnetism of a permanent magnet. Stated differently, a permanent magnet has very high intrinsic coercivity, which is a measure of its resistance to demagnetization. 
     A permanent magnet possesses poles of opposite polarity. The poles are regions of a magnet (usually at the end of the magnets) where the external magnetic field is strongest. Relative to Earth&#39;s magnetic poles, if the magnet is free to turn, one pole will point to the magnetic north pole of the Earth, and is thus called a north pole of the magnet, which is indicated by N in the drawings or otherwise called a N-pole. The opposite pole is called a south pole of the magnet, which is indicated by S in the drawings or otherwise called an S-pole. 
     According to physical laws, poles of like polarity (N-N or S-S) repel each other with a magnetic force. Conversely, poles of unlike polarity (N-S or S-N) attract each other with a magnetic force. Thus, structures  12  and  14  incorporating permanent magnets will repel each other when like poles of the structures  12  and  14  (N-N or S-S) are oriented to face each other, and likewise attract each other when opposite poles of the structures  12  and  14  (N-S or S-N) are oriented to face each other. The magnitude of the force of magnetic attraction or repulsion depends on the strength of the magnets and the distance between the poles. 
     Examples of known permanent magnet materials include alloys of Neodymium-Iron-Boron (NdFeB), alloys of Aluminum-Nickel-Cobalt (AlNiCo), and Samarium Cobalt (SmCo). An electromagnet (current flowing through a coil of wire) can be substituted for a permanent magnet. 
     In the magnetic force systems  10   a ,  10   b , and  10   c  shown in, respectively,  FIGS. 4A to 4D ,  5 A and  5 B, and  6 A and  6 B the magnetic materials  16  and  18  are oriented such that opposite poles (N-S or S-N) generally face each other across lower jaw or across tongue tissue. Thus, the first and second magnetic structures  12  and  14  are referred to as having opposite polarities. The structures  12  and  14  will magnetically interact by the generation of a magnetic force between them. The nature of the magnetic force will generally be called in shorthand for purposes of description an “attracting” magnetic force, because it involves an interaction between magnetic poles of the unlike polarities. However, it should be appreciated that the magnetic force generated between the structures  12  and  14  can include a torquing force (i.e., a force or moment of a force that tends to rotate the internal structure  12  in the more mobile tissue of the tongue and/or soft palate/uvula about an axis), and/or a decentering force (i.e., a force in essentially a lateral or side-to-side direction that tends to offset the internal structure  12  in the tongue and/or soft palate/uvula left or right, again depending the mobile tissue region being targeted), or a combination of two or more attracting, torquing, and decentering forces. One or more of these magnetic forces collectively can prevent the tongue and/or soft palate (depending on the mobile tissue region being targeted) from moving in a posterior direction and closing, obstructing, or restricting the pharyngeal conduit or airway. One of the predominant advantages of the attracting systems is their ability to decrease or eliminate the significant and problematic decentering and torquing forces seen in repelling magnetic systems in treating OSA. 
     It should be appreciated that the structure  12  in the more mobile targeted tissue region can include a ferromagnetic material  16  that is itself not magnetized, but that nevertheless is attracted to a ferromagnetic material  18  on the structure  14  in the less mobile targeted tissue region, which is magnetized. Therefore, the ferromagnetic material(s)  16  of the structure  12  can comprise an un-magnetized material, e.g., ferrous plate, on which the magnetized ferromagnetic material  18  of the structure  14  exerts an attractive magnetic force. The terms “ferromagnetic” material as used in this specification is therefore not necessarily limited to an object that exhibits magnetic properties (i.e., an object that is magnetized), but also encompasses an object made of a material that is not itself magnetized but which is attracted to another object that is magnetized. 
     2. Magnetic Structures 
     As previously described in general terms, the ferromagnetic material  16  of the first structure  12  can be magnetized or un-magnetized. However, it is desirably permanently magnetized and therefore will be described as “magnetic”. The magnetic material  16  is placed in or on tissue in the airway. The term placed “in or on” is intended to mean that the magnetic material  16  can be placed either on surface tissue or implanted within tissue. For longevity and comfort, the material  16  is desirably implanted within tissue. In the illustrated embodiments, the targeted tissue can comprise a region of the tongue, a region of the soft palate/uvula, or both. 
     As previously generally described, the ferromagnetic material  18  of the second structure  14  is also desirably permanently magnetized and therefore will be described as “magnetic”. The magnetic material  18  is placed externally of the airway under the chin or lower jaw, or internally within the airway along the inner or outer edge of the lower teeth, on top of the teeth, or on top of or below the tongue. As previously described, when externally located, the magnetic material  18  is desirably mounted or carried in an individually fitted chin strap or neck collar. When internally located, the magnetic material  18  is desirably mounted or carried in an oral mouthpiece fitted to the lower teeth. In this way, the magnetic material  18  can be located externally under the lower jaw, or internally along the inner or outer edge of the lower teeth, on top of the lower teeth, on top of or below the tongue to magnetically interact with the material  16  placed on or implanted within tissue in a region of the tongue, a region of the soft palate/uvula, or both. 
     The permanent magnetic materials  16  and  18  can each be configured in various ways and take various shapes, e.g., cylindrical, square, rectangular, or other polygons. A given magnetic material  16  or  18  of a given internal component, implant  12  or external component  14  can comprise a single or discrete source of magnetism having a given desired polar orientation. For example, a given magnetic material  16  or  18  can comprise a single permanent magnet, as shown in  FIG. 10 . Bonded permanent magnets may also be used. Bonded magnets can be flexible or rigid, and consist of powdered NdFeB, Ferrite, or SmCo permanent magnet materials bonded in a flexible or rigid substrate of e.g., rubber, nitrile, polyethylene, epoxy, polyvinyl chloride, silicone, rubber, or nylon. The forming of the bonded magnet can be achieved by extrusion, compression molding, injection molding, calendering, or printing. Bonded magnets enable unique flexible designs, and durable high tolerance shapes that are otherwise difficult to achieve. 
     Alternatively, a plurality of permanent magnetic material  16  or  18  can be positioned for placement as an array  22  carried as a unit on a support carrier  24 , or otherwise directly linked together, as shown in  FIG. 11 . The carrier  24  can comprise, for example, a woven, formed, or molded structure made, e.g., from a polymer or fiber or fabric or non-ferrous metallic material. Like the magnetic materials  16 / 18  themselves, the arrays  22  can be variously shaped, sized, and configured for implantation in the intended tissue region (for the first structure  12 ) or for placement in association with external or internal tissue (for the second structure  14 ). 
     In the arrangement shown in  FIG. 11 , the magnetic materials  16 / 18  are placed on the carrier  24  with the N and S-poles facing generally in the same direction. In  FIG. 11 , the N-pole orientation is shown by the arrows, and the S-pole is therefore oriented in an opposite direction. In this way, an array  22  of like permanent magnets  16 / 18  having the relatively similar magnetic orientation (i.e., polarity) can be assembled for orientation as a unit on the carrier  24 . 
     With respect to the first structure  12 , a plurality of permanent magnetic materials  16  (or un-magnetized materials that are attracted to a magnetic material) can be incorporated within a flexible or compliant array  22  and carried as a unit on a support carrier  24  (as shown in  FIG. 11 ) for implantation in tissue. With respect to the second structure  14  (the arrangements shown in  FIG. 7A to 7C ;  FIGS. 8A and 8B ; and  FIGS. 9A to 9E ), a plurality of permanent magnetic materials  18  can be incorporated in a more rigid array  26  carried as a unit on a support carrier  28 . The support carrier  28  can be individually associated with headgear to stabilize its placement on or under the chin ( FIGS. 7A to 7C ), with a neck piece to stabilize its placement about a neck ( FIGS. 8A and 8B ), or with a mouthpiece to stabilize its placement within an oral cavity ( FIGS. 9A to 9E ). Like the magnetic materials  16 / 18  themselves, the array  26  can be variously shaped, sized, and configured. 
     In either arrangement (individually as shown in  FIG. 10  or on an array as shown in  FIG. 11 ), the magnetic material(s)  16  or  18  is/are desirably coated, plated, encapsulated, or deposited prior to placement in or on tissue, or placement in the respective stabilization device (headgear, neck piece, or mouthpiece) with a selected protective material  20  or  30 , respectively. The protective material  20 / 30  is selected to provide a corrosion resistant and biocompatible interface, to prevent interaction between the magnetic material  16 / 18  and tissues or fluids of the body. The protective material  20 / 30  is also desirably selected to form a durable tissue interface, to provide longevity to the system component, and thereby provide resistance to structural fatigue and/or failure. 
     Selected to provide these desired physical and physiologic benefits, the protective material  20  and its application to the material  16  is also desirably selected to avoid imparting added stiffness to the structure  12  itself, to complement its preferred placement by implantation in tissue. However, with respect to the structure  14  (which desirably is not intended to be implanted), the protective material  30  used on material  18  can be and is desirably selected so that it will add stiffness to structure  14 , so as to maximize the attraction between a relatively flexible structure  12  and a relatively immobile and less flexible structure  14 . The more efficient the attraction between materials  18  and  16  is, the smaller the size of ferromagnetic materials  16  and  18 , and thus the lighter and more comfortable the structures  12  and  14 , can be. 
     The protective material  20 / 30  can be selected among various types of materials known to provide the desired biocompatibility, resistance to corrosion, and durability. For example, the protective material  20 / 30  can comprise titanium or other metal material plated, deposited, or otherwise coated upon the magnetic material  16 / 18 . As another example, the protective material  20 / 30  can comprise a parylene coating. As other examples, the protective material  20 / 30  can comprise a silicone polymer, a non-toxic epoxy, a medical grade polyurethane, or a U.V. curable medical acrylic co-polymer. The protective material  20 / 30  may also incorporate anticoagulants and/or antibiotics and/or tissue in-growth promoters. 
     D. Representative Systems of Magnetic Structures 
     1. The Tongue System 
       FIG. 12A  shows a representative Tongue System  10   a  of the type shown in  FIG. 4A . The system  10   a  comprises the ferromagnetic materials  16  and  18  arranged in a relatively similar, attracting orientation, as previously described. In  FIG. 12A , the Tongue System  10   a  includes a first magnetic implant  12  comprising a first magnetic array  22  of a type shown in  FIG. 11  sized and configured for implantation in the tongue. The Tongue System  10   a  also includes a second magnetic component  14  comprising a second magnetic array  26  also of a type shown in  FIG. 11 , but further incorporated into an under-the-chin orientation of a type shown in  FIG. 7C . 
     As shown in  FIG. 12B , the array  22  of the first structure  12  comprises a carrier  24 , on which the array  22  of ferromagnetic material(s)  16  (desirably comprising one or more permanent magnets) is arranged. As  FIGS. 12A and 12B  show, the carrier  24  is shaped along a longitudinal axis to have a length that is longer than its width. The longitudinally-shaped array  22  is sized and configured to be implanted along the anterior-to-posterior axis of the tongue and the airway, respectively. As shown in  FIGS. 12A and 12B , the longitudinal axis of the array  22  extends along the raphé of the tongue. 
     As shown in  FIG. 12C , the array  26  of the second structure  14  comprises a carrier  28 , on which the array  26  of magnetic materials  18  (also permanent magnets) is arranged. The carrier  28  comprises the chin cup shown in  FIG. 7C . In  FIG. 12C , the array  26  is horseshoe-shaped (although many other arrangements are envisioned). The horseshoe-shaped array  26  is placed under the chin and lower jaw. It can be appreciated that a relatively similar or the same orientation of the magnetic materials  18  can be achieved by placing the array  26  in association with a neck piece (as shown in  FIGS. 8A and 8B ) or by placing the array in association with a mouthpiece worn within the oral cavity (as shown in  FIGS. 9A to 9E ). 
     As shown in  FIG. 12C , the horseshoe-shaped array of magnetic materials  18  follows the entire curved anatomy of the oral cavity from posterior to anterior. The array comprises posterior magnetic regions  18   a  (located on opposite sides of the tongue), an anterior magnetic region  18   c  (located along the curved anterior region of the oral cavity), and a middle magnetic regions  18   b  (located between the anterior and posterior regions of the oral cavity on opposite sides of the tongue).  FIG. 12D  shows an alternative embodiment to the horseshoe-shaped array. In this embodiment the magnetic materials  18  are placed both under the chin  18   a ,  18   b , and  18   c , and adjacent to the chin  18   d.    
     When implanted, as  FIG. 12E  shows, poles of the magnetic material  16  of the first implant  12  are oriented to generally align with the opposite poles of the magnetic material  18  of the external component  14  across the airway, that is, either N-S or S-N-poles are generally aligned across the lower jaw or across tongue tissue, in the case of the mouthpiece array. As a result the magnetic external component  14  interacts by attracting the magnetic tongue implant  12  (as indicated by the facing arrows A in  FIG. 12E ). Due to the attracting forces A between implant  12  and structure  14 , the tongue tissue cannot collapse against the pharyngeal conduit during sleep and thus the airway remains patent. However, when an apnea patient is awake, the forces may be overcome by swallowing, speech, coughing, sneezing, etc. Alternatively, the external magnets  18  can be positioned and worn only for purposes of sleeping allowing for higher, more therapeutic forces during sleep which are easily removed to allow normal swallowing and speech function during daytime hours. 
     In an alternative arrangement, as shown in  FIG. 12F , the array of magnetic materials  18  does not symmetrically follow the entire curved anatomy of the oral cavity from posterior to anterior. Instead, the array comprises a posterior magnetic region  18   a , an anterior magnetic region  18   c , and a middle magnetic region  18   b  asymmetrically only along one side of the tongue. In this arrangement, in response to the attracting magnetic forces between the implant  12  implanted in the tongue and the single sided magnetic structure  14  carried by the chin, neck, or teeth, the airway on the side of the tongue farthest from magnets  18  will open up. That side of the tongue will no longer collapse against the pharyngeal wall and apneic episodes will be prevented. 
     In yet another alternative arrangement, as shown in  FIGS. 12G and 12H , the tongue implant  12 ′ is aligned in parallel arrangement to the mouthpiece structure/external component  14 . The magnetic attracting force between the tongue implant  12 ′ and the external component pushes the tongue in an anterior direction. This particular embodiment may be able to generate more force than previous embodiments due to the shorter distance between the tongue implant and the mouthpiece structure. 
     2. The Soft Palate System 
       FIG. 13A  shows a representative Soft Palate System  10   b  of the type shown in  FIG. 5B . The system  10   b  comprises the ferromagnetic materials  16  and  18  arranged in an attracting orientation, as previously described. In  FIG. 13A , the Soft Palate System  10   b  includes a first magnetic implant  12  comprising a first magnetic array  22  of a type shown in  FIG. 11  sized and configured for implantation in the soft palate. The Soft Palate System  10   b  also includes a second magnetic component  14  comprising a second magnetic array  26  also of a type shown in  FIG. 11 , but further incorporated into a mouthpiece orientation (placed outside the lower teeth) of a type shown in  FIG. 9B . 
     As shown in  FIG. 13B , the array  22  of the first structure  12  comprises a carrier  24 , on which the array  22  of ferromagnetic material(s)  16  (desirably comprising one or more permanent magnets) is arranged. As  FIGS. 13A and 13B  show, the carrier  24  is shaped along a longitudinal axis. The longitudinally-shaped array  22  is sized and configured to be implanted along the anterior-to-posterior axis of the soft palate and the airway, respectively. As shown in  FIGS. 13A and 13B , the longitudinal axis of array  22  extends along the midline of the soft palate or uvula. 
     As shown in  FIG. 13C , the array  26  of the second structure  14  comprises a carrier  28 , on which the array  26  of magnetic materials  18  (also permanent magnets) is arranged. The carrier  28  comprises the mouthpiece shown in  FIG. 9B . In  FIG. 13C , the array  26  is horseshoe-shaped to conform to the profile of the lower teeth. It can be appreciated that the same orientation of the magnetic materials  18  can be achieved and stabilized by placing the array  26  in association with a headgear (as shown in  FIGS. 7A and 7B ), chin cup (as shown in  FIG. 7C ), or neck piece (as shown in  FIGS. 8A and 8B ) or by placing the array in association with other mouthpieces worn within the oral cavity (as shown in  FIGS. 9A and 9C  to  9 E). 
     When implanted, as  FIG. 13D  shows, poles of the magnetic material  16  of the first implant  12  are oriented to generally align with the opposite poles of the magnetic material  18  of the external component  14  across the airway, that is, either N-S or S-N-poles are generally aligned across tongue tissue or across the lower jaw, in the case of a chin cup or neck piece array. As a result the magnetic external component  14  interacts by attracting the magnetic soft palate implant  12  (as indicated by the attracting arrows A in  FIG. 13D ). 
     Due to the attracting force between implant  12  and structure  14 , the soft palate does not collapse against the pharyngeal conduit during sleep and thus the airway remains patent. However, when an apnea patient is awake, the forces may be overcome by swallowing, speech, coughing, sneezing, etc. Alternatively, the oral cavity magnets  18  can be positioned and worn only for purposes of sleeping, allowing for higher, more therapeutic forces during sleep which are easily removed to allow normal swallowing and speech function during daytime hours. 
     3. The Combined System 
       FIG. 14A  shows a representative Combined System  10   c  of the type shown in  FIG. 6B . The system  10   c  comprises the ferromagnetic materials  16  and  18  arranged in an attracting orientation, as previously described. In  FIG. 14A , the Combined System  10   c  includes a pair of first ferromagnetic implants  12   a  and  12   b . Each implant  12   a  and  12   b  comprising a ferromagnetic magnetic array  22  of a type shown in  FIG. 11  sized and configured for implantation, respectively, in the tongue and the soft palate. The Combined System  10   c  also includes a second magnetic component  14  comprising a second magnetic array  26  also of a type shown in  FIG. 11 , but further incorporated into a mouthpiece orientation (placed outside the lower teeth) of a type shown in  FIG. 9B . 
     As shown in  FIG. 14A and 14B , the arrays  22  of the first structures  12   a  and  12   b  each comprises a carrier  24 , on which the respective array  22  of ferromagnetic materials  16  (desirably comprising one or more ferromagnets) is arranged. As  FIGS. 14A and 14B  show, the carrier  24  of each structure  12   a  and  12   b  is shaped along a longitudinal axis. The longitudinally-shaped array  22  of the structure  12   b  is sized and configured to be implanted along the anterior-to-posterior axis of the tongue. The longitudinally-shaped array  22  of the structure  12   a  is sized and configured to be implanted along the anterior-to-posterior axis of the soft palate. 
     As shown in  FIG. 14C , the array  26  of the second structure  14  comprises a carrier  28 , on which the array  26  of magnetic materials  18  (also permanent magnets) is arranged. The carrier  28  comprises the mouthpiece shown in  FIG. 9B . In  FIG. 14C , the array  26  is horseshoe-shaped to conform to the profile of the lower teeth. It can be appreciated that the same orientation of the magnetic materials  18  can be achieved and stabilized by placing the array  26  in association with a headgear (as shown in  FIGS. 7A and 7B ), chin cup (as shown in  FIG. 7C ), or neck piece (as shown in  FIGS. 8A and 8B ) or by placing the array in association with other mouthpieces worn within the oral cavity (as shown in  FIGS. 9A and 9C  to  9 E). 
     When implanted, as  FIG. 14D  shows, the magnetic material  16  of both implants  12   a  and  12   b  are generally attracted to the magnetic material  18  of the external component  14  (as indicated by the attracting arrows A in  FIG. 14D ). Due to the attracting forces A between each of the implants  12   a  and  12   b  and the structure  14 , the tongue and the soft palate resist collapse against the pharyngeal conduit during sleep and thus the airway remains patent. However, when an apnea patient is awake, the forces may be overcome by swallowing, speech, coughing, sneezing, etc. Alternatively, the oral cavity magnets  18  can be positioned and worn only for purposes of sleeping allowing for higher, more therapeutic forces during sleep which are easily removed to allow normal swallowing and speech function during daytime hours. 
     The various magnetic force systems  10   a ,  10   b , and  10   c  as described provide an elegant, cost-effective treatment of sleep apnea. Placed in or on tissue in the tongue, soft palate, or uvula, the ferromagnetic structure  12 , along with its companion ferromagnetic structure  14 , is well tolerated and significantly more comfortable and user friendly than the equipment of CPAP and is likely more desirable than other highly intrusive surgical treatment options. The magnetic systems  10   a ,  10   b , and  10   c  offer a sophisticated, yet easy to use design, which can be shaped, configured, and magnetically titrated to meet patients&#39; individual needs, based upon specific anatomic and physiologic requirements, as will be described in greater detail later. 
     III. Moderating the Force-Distance Relationship Forces in Dynamic Tissue Regions 
     A. Generally 
     In the systems  10   a ,  10   b , and  10   c  shown in  FIGS. 12A to 12E ;  13 A to  13 D; and  14 A to  14 D, the magnetic components  12  and  14  are desirably aligned vertically across the lower jaw or across tongue tissue from each other to create an attracting magnetic force field. In reality, there is rarely a theoretically “perfect” magnetic alignment between the magnetic materials  16  and  18 . This is due to the dynamic nature of the tongue and soft palate in the airway. The distance and orientation between the tongue and soft palate, and between each of the tongue and soft palate and the lower jaw varies due to patient-to-patient anatomical variability, as well as the tongue&#39;s and soft palate&#39;s constant movement during sleep and waking hours. There is rarely a geometrically “perfect,” parallel relationship between these tissue structures within the airway. Further, when the tongue or soft palate moves laterally, posteriorly, anteriorly, cranially, caudally, in a rolling manner, or any combinations thereof during sleep, the movement can significantly alter the orientation and alignment between the attracting magnetic materials  16  and  18  from one moment to another. 
     Variations in the force across an implant (or a magnet, or any other object) can manifest as torques, and are present in any magnetic system that is not in perfect alignment. Torque is present in all systems, whether attracting or repelling; when magnets are not in “perfect” alignment, where there is increased misalignment by angle or position, the torque will tend to correct the alignment of the magnets; i.e., they will rotate toward an alignment that maximizes the attracting force. The magnets want to be perfectly aligned in the highest state of attraction possible, in other words to be best aligned with a N-pole facing a S-pole. 
     Magnetic structures placed in or on mobile anatomic structures in the airway are seldom, if ever, orientated in a way that permits theoretically “perfect” or ideal alignment of N-S or S-N attracting poles. The alignment of the attracting magnetic materials is rarely theoretically “perfect” or ideal, and it is subject to continuous change. It is by understanding and controlling the torque inherent in magnetic systems, that the tongue can be effectively manipulated for the therapeutic purposes disclosed herein. 
     B. Design Considerations 
     Any attracting magnetic system involving the tongue and/or soft palate desirably takes into account and balances at least three considerations. One consideration is anatomic—(i) the varying distances and the lack of perfect parallel alignment between the tongue and the soft palate and between each of the tongue and the soft palate and the lower jaw, due to individual upper respiratory anatomy and the natural movement of the tongue relative to the soft palate and relative movement of either the tongue or soft palate to the lower jaw. The other two considerations are physical—(ii) the ability to place implants in the most desired orientation to one another; and (iii) the distance between attracting magnets and the resulting force must also be taken into account, i.e. systems which keep distance relatively short and provide for a tether to apply force at an off-set location. 
     A given attracting tongue or soft palate structure should desirably be maintained in a position of maximal attraction as other structures, such as the tongue, soft palate, or uvula, move in relation to the lower jaw. For example, it should be recognized that during sleep, the tongue will undergo a wide variety of motions and changes of angular orientation to the lower jaw. 
     A given tongue or soft palate structure desirably includes features for maintaining the implant in its close to maximal attracting state at all the angular alignments and varying distances normally and abnormally encountered with respect to the lower jaw, but should still allow for performance of natural bodily functions during sleep, e.g. swallowing. 
     C. Titrated Magnetic Arrays 
     Magnetic force is roughly inversely proportional to the square of the distance between the magnetic structures. Magnetic force is therefore very sensitive to distance. A small increase in distance between attracting magnetic structures can therefore lead to a dramatic decrease in magnetic force between them. The slope of Curve SM in  FIG. 15  demonstrates how the magnitude of a magnetic force field (y-axis) between two single magnet structures (as shown in  FIG. 10 ) decreases significantly with relatively small increases in distance between them (x-axis) due to the inverse-square relationship. 
     The range of distances between magnetic structures  12  and  14  in the systems  10   a ,  10   b , and  10   c  during normal anatomic functions of the tongue and/or soft palate will be in shorthand called the “working range.” It is believed that, in the context of the systems  10   a ,  10   b , and  10   c , the working range lies in a range of about  3   c m to 4 cm. For a given system  10   a ,  10   b , or  10   c , the magnetic structures  12  and  14  are desirably sized and configured so that the magnitude and flux distribution of the magnetic force field is designed or selected so that variations in magnetic force due to variations in distance between the structures  12  and  14  are moderated, at least within the boundaries of the working range. At least within the boundaries of the working range, the titrated magnetic force field provides a variation of magnetic field force with distance that presents a slope having a magnitude less than the slope of curve SM in  FIG. 15 . Again, within the boundaries of the working range, the slope of the magnetic force field diminishes substantially, thereby reducing the sensitivity of the force-distance relationship. In the systems  10   a ,  10   b , and  10   c  shown in  FIGS. 12A to 12D ;  13 A to  13 D; and  14 A to  14 D, the magnetic structure  14  is desirably sized and configured to provide one or more field direction(s) such that the magnetic structure  14  maintains a relatively constant magnetic field and attracting force with the internal structure  12  despite relative movement of the tongue, soft palate, or uvula in the normal performance of bodily functions. 
     During the normal performance of bodily functions, the separation between the centers of mass of the structures  12  and  14  will vary within the working range between a distance δ FAR  (expressed in units of centimeters) where the centers of mass of the structures  12  and  14  are placed farthest apart and a distance δ NEAR  (expressed in units of centimeters) where the centers of mass of the structures  12  and  14  are placed closest together. At the distances δ FAR  and δ NEAR  there will be a resulting magnetic force, respectively δ FAR  (expressed in units of grams) and F NEAR  (expressed in units of grams) of the magnetic force system, which will vary roughly inversely proportional to the square of the respective far and near distances of the working range, or (1/δ FAR   2 ) and (1/δ NEAR   2 ), respectively. The magnetic structures  12  and  14  are desirably mutually sized and configured so that variations in magnetic force due to various in distance between the magnetic structures  12  and  14  within the working range maintain a relationship, as follows:
 
( F   NEAR   /F   FAR )≦(δ FAR   2 /δ NEAR   2 )
 
     In this way, the magnetic structure  14  maintains a relatively constant magnetic field and attracting force with the internal structure  12  despite relative movement of the tongue, soft palate, or uvula within the working range in the normal performance of bodily functions. 
     To achieve this objective, the systems  10   a ,  10   b , and  10   c  desirably include magnetic structures  12  and  14  comprising arrays of magnets like that shown in  FIG. 11 . Arrays of magnetic materials  16  and  18  provide a more uniform distribution of magnetic field and attracting force with the internal structure  12  within the desired working range. Arrays of magnetic materials  16  and  18  also make it possible to control the magnitude and distribution of the magnetic field between the structures  16  and  18  to moderate the sensitivity of the force-distance relationship within the working range. Larger, smaller, or different arrays of magnetic materials  16  and  18  can be used to titrate the uniform attracting force with internal structure  12  and external magnet  14 . 
     For example, the magnetic structure  14  shown in  FIGS. 16A and 16B  includes an array of magnets comprising distinct spatial magnetic regions  18   a ,  18   b , and  18   c  having different polarities. The magnetic regions  18   a ,  18   b , and  18   c  are sized and configured for use in association with an implanted magnetic structure  12  to form a Tongue System  10   a , or a Soft Palate System  10   b , or a Combined System  10   c . In  FIGS. 16A and 16B  the magnetic structure  12  also comprises an array of magnetic regions  16   a ,  16   b , and  16   c  implanted in the tongue, or soft palate/uvula, or both the tongue and soft palate/uvula. 
     As shown in  FIGS. 16A and 16B , the spatially distinct magnetic regions  16   a ,  16   b , and  16   c  can each comprise a single magnet or an array of individual magnets of common polarity (as shown in  FIG. 11 ) arranged on a carrier. The array of spatially distinct magnetic materials  16   a ,  16   b , and  16   c  can be sized and configured to follow the curved anatomy of the oral cavity from posterior to anterior. 
     The structure  14  comprises posterior magnetic regions  18   a  (located on opposite sides of the tongue), an anterior magnetic region  18   c  (located along the curved anterior region of the oral cavity), and a middle magnetic region  18   b  (located between the anterior and posterior regions of the oral cavity on opposite sides of the tongue). The array of magnetic regions  18   a ,  18   b , and  18   c  shown in  FIG. 16A  is sized and configured for particular use in a chin-mounted or mouth piece configuration, as previously discussed and as shown, respectively, in  FIGS. 7A to 7C  and  FIGS. 9A to 9E . The array of magnetic regions  18   a ,  18   b , and  18   c  shown in  FIG. 16B  is sized and configured for particular use in a neck piece configuration, as previously described and as shown in  FIGS. 8A and 8B . 
     As shown in  FIGS. 16A and 16B , the N-poles of the magnetic regions  18   a ,  18   b , and  18   c  in the headgears, chin cup, mouth piece, or neck arrays are mutually oriented differently both with respect to each other and with respect to the S-poles of the magnetic materials  16  implanted in the airway in the tongue and/or soft palate. The mutually different orientations of the N-poles of the magnetic regions  18   a ,  18   b , and  18   c  provide a titrated magnetic field force that moderates the sensitivity of force-to-distance relationship between the magnetic materials  16  and  18  in the working range. 
     More particularly, as  FIGS. 16A and 16B  show, the orientation of the N-poles of the spatially distinct magnetic regions  18   a ,  18   b , and  18   c  varies from posterior to anterior with respect to the S-poles of the magnetic regions  16   a ,  16   b , and  16   c . As  FIGS. 16A and 16B  show, the anterior magnetic region  18   c  (spanning the front of the oral cavity) has a N-pole orientation directed toward the oral cavity, in a facing relationship with the S-poles of the magnet regions  16   a ,  16   b , and  16   c . As the region  18   c  curves to conform to the curved anatomy of the anterior oral cavity, the orientation of the N-poles of the magnetic region  18   c  likewise changes to always point inwards toward the S-poles of the magnetic regions  16   a ,  16   b , and  16   c . The N-S orientation between the anterior magnetic region  18   c  of the structure  14  and the anterior magnetic regions  16   a ,  16   b , and  16   c  of the structure  12  generates an attracting magnetic field (attracting arrows A) in the anterior region of the oral cavity. The attracting magnetic field A resists posterior movement of the tongue and/or soft palate/uvula, which is a desired therapeutic objective. 
     The posterior magnetic regions  18   a  of the structure  14  (located on opposite sides of the tongue in the back of the oral cavity) have a N-pole orientation toward the oral cavity. The magnetic region  18   a  thereby presents N-poles oriented in a generally facing relationship with the N-poles of the magnet regions  16   a ,  16   b , and  16   c , which are located in the posterior of the tongue and/or soft palate/uvula. The N-N orientation between the posterior magnetic regions  18   a  of the structure  14  and the posterior magnetic regions  16   a ,  16   b , and  16   c  of the structure  12  generates a repelling magnetic field (repelling arrows R) in the posterior region of the oral cavity. The fluxes of the arrays interact to create an anterior directed force, which is relatively stable where the implant is well-aligned in a medial-lateral direction. 
     In this arrangement, the middle magnet regions  18   b  of the structure  14  (between the posterior and anterior magnetic regions  18   a  and  18   c  on opposite sides of the tongue along the lateral sides of the oral cavity) have a N-pole orientation toward the anterior magnetic region  18   c . Juxtaposed between the attracting magnetic field in the anterior region of the oral cavity and the repelling magnetic field in the posterior region of the oral cavity, the N-pole orientation of the middle magnetic region  18   b &#39;s direct flux in the magnetic field between the anterior magnetic region  18   c &#39;s (which attracts the tongue and/or soft palate/uvula at the anterior region of the oral cavity) and the posterior magnetic region  18   a &#39;s (which repels the tongue and/or soft palate/uvula at the posterior region of the oral cavity), without imposing a significant destabilizing side-to-side attracting force on the tongue and/or soft palate. The magnetic regions  18   a ,  18   b , and  18   c  have been sized and configured to create a relatively constant magnetic flux or a relatively constant magnetic flux gradient in the working range where the implant  12  is expected to be positioned. 
     The magnetic regions  18   a ,  18   b , and  18   c  shown in  FIGS. 16A and 16B  can be variously constructed. For example,  FIGS. 17A and 17B  are illustrative examples of magnetic arrays comprising seven separate permanent magnets  18 ( 1 ) to  18 ( 7 ), whose N-polarities have been labeled.  FIG. 17A  is directed to a chin-mounted or mouth piece structure, like  FIG. 16A .  FIG. 17B  is directed to a neck-collar structure, like that in  FIG. 16B . 
     Magnets  18 ( 1 ) and  18 ( 7 ) each comprise a posterior magnetic region  18   a . Magnets  18 ( 3 ),  18 ( 4 ), and  18 ( 5 ) collectively comprise the anterior magnetic region  18   c . Magnets  18 ( 2 ) and  18 ( 6 ) each comprise a middle magnetic region  18   b . As shown in  FIGS. 17A and 17B , the magnetic fields can be manipulated by changing direction of the magnets themselves. 
       FIG. 15  illustrates (Curve MM) the force versus distance relationship between arrays  12  and  14  as shown in FIGS.  16 A/B and FIGS.  17 A/B, as just described. The slope of Curve MM in  FIG. 15  demonstrates how magnitude of a magnetic force field (y-axis) between the two arrays  12  and  14  (as shown in FIGS.  16 A/B or  17 A/B) does not decrease significantly within the boundaries of the working range (x-axis). Curve MM further demonstrates that the slope diminishes substantially within the boundaries of the working range. 
       FIG. 18A  is a diagrammatic representation of a finite element analysis showing the flux direction lines for the magnetic arrays of a type shown in FIGS.  16 A/B and  17 A/B.  FIG. 18B  is another diagrammatic representation of a finite element analysis showing distribution of the magnetic field force for these magnetic arrays  16   a / 16   b / 16   c  and  18 ( 1 ) to  18 ( 7 ). As seen in  FIG. 18B , the arrays generate a titrated magnetic field F 1 /F 2 /F 3  having a force that generates a relatively constant force F 3  over a working range of 3 cm to 4 cm. This relatively constant magnetic field force F 3  allows the structure  12  implanted in the tongue, soft palate, or uvula to vary in its position within the working range due to normal functions without significant loss of attracting magnetic force with respect to the structure  14 . 
     D. Tethered Magnetic Structures  FIGS. 39A and 39C  show representative embodiments of a tethered ferromagnetic structure  120  implanted in an anterior region of a tongue in proximity to a magnetic structure  14  as previously described, e.g., a mouthpiece carried within the oral cavity or an external carrier placed on or under the chin or about the neck. For purposes of illustration,  FIG. 39A  shows the magnetic structure  14  worn externally under the chin, while in  FIG. 39C  the magnetic structure  14  is part of a chin cup. As seen in  FIGS. 39A and 39C , the ferromagnetic structure  120  includes one or more permanent magnets or ferromagnetic materials implanted in tissue beneath the tongue or in an anterior region of the tongue, respectively. In use, the ferromagnetic structure  120  in the tongue magnetically interacts with the magnetic structure  14 . The ferromagnetic structure  120  and the magnetic structure  14  are arranged in an attracting orientation, to draw the tongue forward and/or resist posterior movement of the tongue in a manner that would otherwise occlude the airway. 
     Due to the relatively close proximity of the ferromagnetic structure  120  to the magnetic structure  14 , the magnitude of the magnetic force field is maximized. Further, to resist migration of the ferromagnetic structure  120  within tissue in the presence of the relatively strong magnetic force field, the ferromagnetic structure  120  further includes an anchoring system  122 . The anchoring system  122  comprises a non-magnetic holding or anchoring structure  124  that is tethered by a band, suture, or another means for attachment  126  to the ferromagnetic structure  120 . The presence of the anchoring system  122  resists migration of the ferromagnetic structure  120  within tissue as a result of the magnetic interaction with the magnetic structure  14 . Furthermore, the anchoring system pulls the posterior tongue tissue in an anterior direction to prevent collapse of the tongue. The anchoring system  122  may also serve to stabilize the ferromagnetic structure  120  in a relatively large, soft tissue mass, such as the tongue. 
     As shown in  FIGS. 39A and 39C , the anchoring structure  124  is implanted in a tissue mass spaced from and posterior to the ferromagnetic structure  120 , e.g., at the back of the tongue. The anchoring structure  124  can comprise, e.g., a biocompatible woven, formed, or molded structure made from a polymer or fiber or fabric or non-ferrous metallic material, which resists deterioration, while exhibiting sufficient flexibility to prevent discomfort or affecting speech or swallowing. As shown in  FIGS. 39A and 39C , the holding structure  124  may include perforations  128 . The perforations  128  impart greater flexibility to the holding structure  124 . The perforations  128  also accommodate tissue in-growth, further securing implantation in tissue. Alternatively (as shown in  FIG. 39E ), the anchoring structure  124  can comprise an expandable umbrella-like structure  142  that collapses for implantation (as shown in sold lines in  FIG. 39E ) and that expands in situ at the implantation site (as shown in phantom lines in  FIG. 39E ). 
     The means for attachment  126  couples or tethers the ferromagnetic structure  120  to the holding or anchoring structure  124 . The means for attachment  126  may comprise a generally non-elastic material, e.g., a non-resorbable suture material, other woven biocompatible lacing or fabric, or a non-woven polymer strip such as nylon or acetal or a biocompatible metallic material such as nickel titanium alloy (Nitinol®). The means for attachment  126  may comprise a biocompatible stem with perforations to permit tissue in-growth and may also include barbs or hooks deploying form the stem, to further stabilize the tethered ferromagnetic structure. Alternatively (as shown in  FIG. 39F ), the means for attachment  126  may be sized and configured to be passed or threaded through an aperture  144  in the anchoring structure  124  and locked into a position of tension, e.g., using a suture lock  146  or knot. This arrangement makes it possible to adjust and control tension within the implant either during initial implantation or subsequent to the initial implantation, or both. 
     In an alternative embodiment, the means for attachment  126  may comprise more elastic materials, to provide compliance and increased comfort for the patient. For instance, when swallowing, the tongue moves in a posterior direction and elasticity may prevent arousal from sleep and further may avoid migration of the ferromagnetic structure  120 . The anchoring structure  124  is desirably wider than the means for attachment  126 , thereby providing the desired resistance for the implanted ferromagnetic structure  120  against being pulled through or out of the implanted tissue region during its magnetic interaction with the close-by magnetic structure  14 . 
     As shown in  FIGS. 39B ,  39 D,  39 E, and  39 F, the ferromagnetic structure  120  may be individually tethered to two or more anchoring structures  124  by respective means for attachment  126 . 
     In this arrangement, the desired physiologic response (resistance of airway tissue collapse) is achieved by the magnetic structure  14  (e.g., on head gear or a mouthpiece, as previously described) creating a magnetic field that interacts with tethered ferromagnetic structure  120  implanted in the caudal anterior (front) section of the tongue or below the tongue. The implanted ferromagnetic structure  120  has a magnetic orientation opposite to the magnetic orientation of the magnetic structure  14 . The magnetic force between opposite magnetic orientations creates an attracting force. As a result of the attracting force, the tongue is drawn forward, toward the front of the oral cavity, to resist an occlusion of the airway at the base of the tongue. 
     The tether attached to the magnetic structure  120  serves to efficiently transfer the motion or movement of structure  120  to the base of the tongue (the site of the obstruction). The use of the tether is designed to avoid the situation where a magnet in the tongue positioned so as to be moved by application of an external magnet  14  is moved anteriorly, but that motion does not translate to motion of the tongue base at the pharyngeal wall. 
     E. Anterior Tongue/Hyoid Muscle Magnetic Structures 
       FIG. 40A  shows a representative embodiment of a ferromagnetic structure  120  implanted in an anterior or caudal anterior region of a tongue, or in one or more hyoid muscles such as the suprahyoid muscles, e.g., the mylohyoid muscles, and/or geniohyoid muscles, and/or stylohyoid muscles, and/or digastric muscles, in proximity to previously-described structure  14 , e.g., a mouthpiece carried within the oral cavity or an external carrier placed on or under the chin or about the neck. For purposes of illustration,  FIG. 40A  shows the structure  14  worn externally under the chin; however, the structure  14  can comprise a removable oral appliance fitted over the teeth in the oral cavity or located in the vestibule of the mouth. As seen in  FIG. 40A , the ferromagnetic structure  120  includes one or more permanent magnets or ferromagnetic materials  16  implanted in tissue beneath the tongue or in an anterior region of the tongue, respectively. In use, the ferromagnetic structure  120  in the tongue magnetically interacts with structure  14 . The ferromagnetic structure  120  and structure  14  are arranged in an attracting orientation, to draw the tongue forward and/or resist posterior movement of the tongue in a manner that would otherwise occlude the airway. 
     In an alternative embodiment shown in  FIG. 40B , the anteriorly-placed ferromagnetic structures  16  are smaller in size than the posteriorly-placed ferromagnetic structures. The posteriorly-placed ferromagnetic structures  16  are larger because the ferromagnetic structure  120  needs to exert a stronger force on the posterior side than on the anterior side, so as to keep the tongue from collapsing and closing off the airway. Furthermore, the posterior end of ferromagnetic structure  120  also contains an aperture  121  through which the structure may become attached or anchored to the hyoid bone. As seen in  FIG. 40C , another alternative embodiment consists of a ferromagnetic structure  120  which is smooth on one side, while the embedded ferromagnetic structures project from the opposite side. 
     As seen in  FIGS. 40A to 40C , due to the relatively close proximity of the ferromagnetic structure  120  to structure  14  as well as the large area covered by ferromagnetic structure  120 , the magnitude of the magnetic force field is maximized. 
     In this arrangement, the desired physiologic response (resistance of airway tissue collapse) is achieved by structure  14  (e.g., on head gear or a mouthpiece, as previously described) creating a magnetic field that interacts with ferromagnetic structure  120  implanted in the caudal anterior (front) section of the tongue or below the tongue. The implanted ferromagnetic structure  120  has a magnetic orientation opposite to the magnetic orientation of structure  14 . The magnetic force between opposite magnetic orientations creates an attracting force. As a result of the attracting force, the tongue is drawn forward, toward the front of the oral cavity, to resist an occlusion of the airway at the base of the tongue. 
     IV. Other Representative Magnetic Structures for Dynamic Tissue Regions 
     A. Self-centering Magnetic Structures 
       FIG. 19  shows in a diagrammatic way a magnetic system comprising two magnetic structures  12  and  14 . As described before, the structures are sized and configured to be placed in or on spaced apart tissue regions in a mutually aligned orientation that generates magnetic interaction between the two structures. Depending upon the polarities of the two structures  12  and  14 , the magnetic interaction can comprise, either a magnetic attracting force between the two structures, to resist movement of the two tissue regions away from each other, or a magnetic repelling force between the two structures, to resist movement of the two tissue regions toward each other, or a combination of these and other forces. 
     As stated before, unless the structures  12  and  14  are aligned in a theoretically ideal fashion, the magnetic interaction will urge the most mobile of the structures (in  FIG. 19 , the structure  12 ) to seek an alignment with the least mobile of the structures (in  FIG. 19 , the structure  14 ) closest to the theoretically ideal position. Under these circumstances, the better the structures  12  and  14  are aligned, the less magnetic force is lost and the less torque is experienced by the most mobile structure. Practically speaking from both an anatomic and surgical perspective, it is difficult to achieve and maintain theoretically ideal alignment of magnetic structures carried in or on tissue. Given this difficulty, due to misalignment, a surgically implanted magnetic system may dissipate some or a large part of the intended magnetic force. 
     In the system shown in  FIG. 20A , at least one of the structures  12  or  14  comprises a self-centering magnetic structure  130 . The self-centering magnetic structure  130  comprises at least one mobile magnet  132  enclosed in a capsule or container  134 . The shape of the mobile magnet  132  relative to the capsule or container  134  is configured and sized to permit the mobile magnet  132  to translate or move freely within the boundaries of the capsule or container  134  in response to misaligned magnetic interaction with the other structure  14 . For example, as shown in  FIG. 20A , when misalignment between the self-centering structure  130  and the other structure  14  occurs, the mobile magnet  132  in the self-centering structure  130  will translate or move within the boundaries of the capsule or container  134  (as shown in  FIG. 20B ) to seek a theoretically ideal alignment with respect to the other structure  14 . As relative tissue orientations dynamically change, the mobile magnet  132  will also dynamically translate or move within the boundaries of the capsule or structure  134  to maintain the best possible alignment with the other structure. The boundaries of the capsule or container  134  provide a region of open space  136  where the mobile magnet can maneuver relatively unimpeded to seek the best possible alignment with the other structure. In  FIGS. 20A and 20B , a Tongue System  10   a  is shown for purposes of illustration. As shown in  FIGS. 20A and 20B , the Tongue System  10   a  comprises a self-centering magnetic tongue implant  130  interacting with an internal magnetic array  14 . 
     As shown in  FIG. 21A , the self-centering magnetic structure  130  may comprise a magnetic structure  14  like that previously described that is sized and configured to be placed in or on tissue outside an airway, e.g., comprising a carrier worn on the chin or about the neck. In this arrangement, the self-centering magnetic structure is intended to be placed in association with another magnetic structure  12  sized and configured to be placed in or on tissue within an airway, e.g., on the tongue, soft palate/uvula, or both. Together, the self-centering structure and the other structure  12  form a system  10   a ,  10   b , or  10   c , as previously described. In  FIG. 21A , a Tongue System  10   a  is shown for purposes of illustration. As shown in  FIG. 21A , the Tongue System  10   a  comprises a tongue implant  12  interacting with an external, self-centering magnetic structure  130 . 
     As shown in  FIG. 21B , the self-centering magnetic structure  130  can comprise a carrier  26  that includes at least one capsule  134  housing at least one mobile magnet  132 . In the embodiment shown in  FIG. 21B , the capsule  134  is compartmentalized for purposes of illustration into two spatially separate zones Z 1  and Z 2 , each housing at least one mobile magnet  132  (generally corresponding to the posterior and intermediate regions  18   a  and  18   b  shown in  FIG. 12C ). In the arrangement, the most anterior magnetic region (region  18   c  in  FIG. 12C ) can comprise one or more magnets that are not mobile, or vice versa. In the embodiment shown in  FIG. 21C , the capsule  134  is compartmentalized for purposes of illustration into three separate zones Z 1 , Z 2 , and Z 3  (generally similar to the regions  18   a ,  18   b , and  18   c  in  FIG. 12C ), each housing at least one mobile magnet  132 . The zones Z 1 , Z 2 , and Z 3  can also be viewed as being separate capsules  134 . As shown in  FIG. 21B and 21C , each zone or capsule may contain a plurality of smaller mobile magnets, commensurate with the available volume of the zone or capsule, allowing the mobile magnets to move freely and align themselves within the capsule with the other structure  12 . The separate zones Z 1 , Z 2 , and Z 3  or capsules  134  keep the mobile magnets  132  in spatial zones, so that the mobile magnets  132  do not congregate in one location. Each zone Z 1 , Z 2 , and Z 3  or capsule  134  is sized and configured to accommodate allowable, defined and controlled movement of the mobile magnet or magnets  132  housed within its boundaries. Alternatively, as shown in  FIG. 21D , any or all zones Z 1 , Z 2 , or Z 3  or capsules  134  may contain a single, larger mobile magnet  132 . 
     As shown in  FIGS. 21E and 21F , the self-centering magnetic structure  130  can include a single zone or capsule that is centrally located, to be, in use, essentially under the tongue. The zone or capsule  134  can accommodate a single, larger mobile magnet  132  (as shown in  FIG. 21E ) or more than one smaller mobile magnet  132  in the centrally-located zone or capsule  134  that is essentially located under the tongue (as shown in  FIG. 21F ). 
     Because the self-centering magnetic structures  130  shown in  FIGS. 21A to 21F  are intended to be placed on external tissue, the internal volume of the zones or capsules can be relatively large (compared to a capsule in a structure that is intended to be implanted in tissue), thereby providing a relatively large freedom of movement for the mobile magnet it houses. 
     Alternatively, as shown in  FIG. 22A , the self-centering magnetic structure  130  can be sized and configured for placement within an oral cavity, e.g., inside, outside, or on top of the lower or upper teeth, as has already been described. In this arrangement, the self-centering magnetic structure  130  is intended to be placed in association with another magnetic structure (in  FIG. 22A , magnetic structure  12 ) sized and configured to be placed in or on tissue within an airway, e.g., on the tongue, soft palate/uvula, or both. Together, the self-centering structure and the other structure  12  form a system  10   a ,  10   b , or  10   c , as previously described. In  FIG. 22A , a Soft Palate System  10   b  is shown for purposes of illustration. The Soft Palate System  10   b  in  FIG. 22A  comprises a soft palate implant  12  interacting with an internal, self-centering magnetic structure  130 . 
     In this embodiment, like the embodiments shown in  FIGS. 21A to 21F , the self-centering magnetic structure  130  comprises at least one capsule  134  housing at least one mobile magnet  132 . In  FIG. 22B , like  FIG. 21B , the capsule  134  is compartmentalized for purposes of illustration into one or more separate spatial zones Z 1  and Z 2  each sized and configured to accommodate unimpeded movement of at least one mobile magnet  132  within its boundaries. As before stated, the zones Z 1  and Z 2  can also be viewed as being separate capsules  134 . The separate zones Z 1  and Z 2  or capsules  134  keep the mobile magnets  132  in spatial zones, so that the mobile magnets  132  do not congregate in one location. Because the structure shown in  FIG. 22B  is intended to be placed within the airway, the internal volume of the zones Z 1  and Z 2  or capsules  134  will be relatively smaller, compared to a capsule in a structure like that in  FIG. 21B , which is intended to be externally worn. Still, the zones Z 1  and Z 2  or capsules  134  and mobile magnets  132  they house can be mutually sized and configured to provide a relatively large freedom of movement for the mobile magnets  132 . As shown in  FIG. 22B , each zone Z 1  and Z 2  or capsule  134  may contain a single mobile magnet, or alternatively, as shown in  FIG. 22C , each zone or capsule  134  may be compartmentalized to contain a plurality of smaller mobile magnets  132 . The number of zones and/or mobile magnets can vary, as shown in  FIGS. 21A to 21F . Also, as previously described, a given structure  14  can include both mobile magnets  132  and non-mobile magnets  18  (for example  18   c  shown in  FIG. 21B ). Many variations are contemplated. 
     As shown in  FIG. 23A , the self-centering magnetic structure  130  may comprise a magnetic structure  12 , like that previously described, that is sized and configured to be placed in or on tissue inside an airway, e.g., comprising a carrier placed in or on a tongue and/or a soft palate/uvula, as has already been described. In this arrangement, the self-centering magnetic structure  130  is intended to be placed in association with another magnetic structure  14  sized and configured to be placed in or on tissue outside an airway (on the chin or neck) or inside the airway (on the lower teeth). Together, the self-centering structure and the other structure  12  form a system  10   a ,  10   b , or  10   c , as previously described. In  FIG. 23A , a Tongue System  10   a  is shown for purposes of illustration. The Tongue System  10   a  in  FIG. 23A  comprises a self-centering tongue implant structure  130  interacting with an external magnetic structure  14 . In this arrangement, the interaction between the self-centering tongue implant structure  130  and the external structure  14  places a torque on the tongue. It should be appreciated that other structures  14  can also comprise a self-centering external structure of a type shown in FIGS.  21 A/B/C/D/E/F or a self-centering internal structure of a type shown in FIGS.  22 A/B/C. 
     In this embodiment, like the previous embodiments shown in FIGS.  21 A/B/C/D/E/F and  22  A/B/C, the self-centering magnetic structure  130  comprises at least one capsule  134  housing at least one mobile magnet  132 . In  FIG. 23B , like  FIGS. 21B and 22B , the capsule  134  is compartmentalized into separate spatial zones Z(N) sized and configured to accommodate unimpeded movement of at least one mobile magnet  132  within its boundaries. In  FIG. 23B , there are eight zones shown (i.e., N=8). These zones Z(N) can also be viewed as separate capsules  134 . As before described, the separate zones Z(N) or capsules  134  keep the mobile magnets  132  in spatial zones, so that the mobile magnets  132  do not congregate in one location. Because the structure  130  shown in  FIG. 23B  is intended to be placed within a tongue or soft palate, the internal volume of the zones Z(N) or capsules  134  will be relatively smaller, compared to a capsule in a structure like that in  FIG. 21B , which intended to be externally worn. Still, the zones Z(N) or capsules  134  and mobile magnets  132  they house can be mutually sized and configured to provide a relatively large freedom of movement for the mobile magnets  132 . As shown in  FIG. 23B , any or all zones Z(N) or capsules  134  may contain a single mobile magnet  132 , or alternatively, as shown in  FIG. 23C , any or all zones Z(N) or capsule  134  may be compartmentalized to contain a plurality of smaller mobile magnets  132 . The number of zones and/or mobile magnets can vary, as shown in  FIGS. 21A to 21F . Also, as previously described, a given structure  14  can include both mobile magnets  132  and non-mobile magnets  18  (like that shown in  FIG. 21B ). Many variations are contemplated. 
     As shown in FIGS.  24 A/ 24 B/ 24 C the mobile magnet  132  housed within a given capsule  134  or zone can comprise various shapes. For example, the mobile magnet  132  may have either a disk-like or spherical configuration ( FIG. 24A ), or a cylindrical configuration ( FIG. 24B ), or a triangular configuration ( FIG. 24C ). The shape can be selected to affect the manner in which the mobile magnet  132  moves or translates within the capsule. For example, the mobile cylindrical magnet  132  ( FIG. 24B ) can roll easily within the capsule  134  in order to align in a proper position. The mobile triangular magnet  132  ( FIG. 24C ) can include a base having a stronger magnetic flux than the apex of the triangle, to help direct flux in a desired direction. 
     B. Off-Center Magnetic Structures 
     The tissue on the lateral sides of the tongue, due to its decreased thickness, may be easier to move than the tissue along the midline of the tongue. Thus, a magnetic structure that is placed in or on tissue on only one side of the tongue can effectively repel a correspondingly positioned magnetic implant in or on a pharyngeal wall. 
       FIG. 25  shows a cross-section of a collapsed pharyngeal conduit, like  FIG. 3  but shown from another perspective, sufficient to cause an apneic episode.  FIG. 25  also shows the tongue with an implanted magnetic structure  70 . Magnetic tongue structure  70  comprises at least two magnets  16  oriented in the same direction, substantially perpendicular to the midline of the tongue. As can be seen in  FIG. 25 , the location of magnetic tongue structure  70  is generally perpendicular and off-center with respect to the raphé of the tongue. That is, as the embodiment in  FIG. 25  shows, all of the structure  70  occupies one side of the tongue along the raphé. Essentially no part of the structure  70  (and therefore no magnets) extends across the raphé to the opposite side of the tongue. 
       FIG. 26A  shows a new position of the tongue (compared to  FIG. 25 ) due to the interactions between the off-center magnetic tongue structure  70  and an external magnetic structure  14  of the type shown in FIG.  12 C/E, which together form an embodiment of a Tongue System  10   a . Forces of magnetic attraction between the off-center structure  70  and the structure  14  in  FIG. 26A  pull the off-center structure  70  anteriorly toward the pharyngeal wall, opening one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
       FIG. 26B  shows a new position of the tongue (compared to  FIG. 25 ) due to the interactions between the off-center magnetic tongue structure  70  and an external magnetic structure  14  of the type shown in  FIG. 12F , which form another embodiment of a Tongue System  10   a . Forces of magnetic attraction between the off-center structure  70  and the structure  14  in  FIG. 26B  pull the off-center magnetic structure  70  toward the opposite side of the tongue with respect to the location of the off-center magnetic structure  70 , opening one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
       FIG. 27  shows a new position of the tongue (compared to  FIG. 25 ) due to the interactions between the off-center magnetic tongue structure  70  and an internal magnetic structure  14 ′ placed in or on the posterior pharyngeal wall across from the region of the tongue where the off-center magnetic structure  70  is implanted. The internal magnetic structure  14 ′ carries one or more magnets  18  having a polarity facing the airway that is the same as the off-center magnetic structure  70 . The off-center magnetic structure  70  magnetically interacts with the pharyngeal wall structure  14  by repelling. Forces of magnetic repulsion between the off-center structure  70  and the structure  14  in  FIG. 27  push the magnetic tongue structure  70  anteriorly toward the mouth, opening one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
     C. Rudder-Type Magnetic Structures 
       FIG. 28  shows a cross-section of a collapsed pharyngeal conduit, like  FIG. 3  but shown from another perspective, sufficient to cause an apneic episode.  FIG. 28  also shows the tongue with an implanted, rudder-type magnetic structure  72 . The magnetic structure  72  comprises a first region or arm  74  carrying at least two magnets  16  oriented in the same direction transversally along the midline of the tongue. As can be seen in  FIG. 28 , the location of the magnets  18  in the arm  74  is off-center with respect and generally perpendicular to the raphé of the tongue, as previously described with respect to  FIG. 25 . However, unlike the embodiment shown in  FIG. 25 , the magnetic structure  72  includes a second region or arm  76  that extends across the raphé to the opposite side of the tongue. The region or arm  76  is free or essentially free of magnets, so that essentially no magnets occupy this region of the tongue. 
     The magnet-free region or arm  76 , which extends to a location of the tongue not occupied by the magnets  16 , acts as a rudder. Rudder-type magnetic structures  72  of the type shown in  FIG. 28  are variants of the off-center magnetic structures  70  shown in  FIG. 25 . The presence of the rudder  76  serves to move more soft tissue than the off-center structure  70  shown in  FIG. 25  and/or to further stabilize the structure  72  during use. 
       FIG. 29A  shows a new position of the tongue (compared to  FIG. 28 ) due to the interactions between the rudder-type magnetic structure  72  and an external magnetic structure  14  of the type shown in  FIGS. 12C and 12E , which together form an embodiment of a Tongue System  10   a . Forces of magnetic attraction between the rudder-type structure  72  and the structure  14  in  FIG. 29A  pull the magnetic portion of the tongue structure  72  anteriorly toward the mouth. This is because the magnets  16  of the structure  72  have an S-polarity facing toward the front (anterior) of the oral cavity, and the magnets  18  of the structure  14  have an opposite N-polarity facing inward toward the oral cavity, or vice versa. The rudder portion  76 , being essentially free of magnets, is not magnetically attracted, but remains implanted in tissue across the raphé on the other side of the tongue. As a result, the structure  72  will pivot about the rudder portion  76  toward the external magnetic structure  14 . The additional surface area of the rudder portion  76  will draw more tissue in the direction of the pivot, and will also serve as a tissue anchor that lends overall stability to the structure  72 . The magnetic interaction opens one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
       FIG. 29B  shows a new position of the tongue (compared to  FIG. 25 ) due to the interactions between the rudder-type magnetic structure  72  and an external magnetic structure  14  of the type shown in  FIG. 12F , which form another embodiment of a Tongue System  10   a . Forces of magnetic attraction between the rudder-type structure  72  and the structure  14  in  FIG. 29B  pull the magnetic portion  76  of the rudder-type magnetic portion of the tongue structure  72  toward the opposite side of the tongue with respect to the location of the magnetic portion of the structure  72 . This is because the magnets  16  of the structure  72  have an S-polarity facing toward the front (anterior) of the oral cavity, and the magnets  18  of the structure  14  have an opposite N-polarity facing inward toward the oral cavity, or vice versa. The rudder portion  76 , being essentially free of magnets, is not magnetically attracted, but remains implanted in tissue across the raphé on the other side of the tongue. As a result, the structure  72  will pivot about the rudder portion toward the external magnetic structure  14 . The additional surface area of the rudder portion  76  will draw more tissue in the direction of the pivot, and will also serve as a tissue anchor that lends overall stability to the structure  72 . The magnetic interaction opens one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
       FIG. 30  shows a new position of the tongue (compared to  FIG. 28 ) due to the interactions between the rudder-type magnetic structure  72  and an internal magnetic structure  14  placed in or on the posterior pharyngeal wall across from the region of the tongue where the rudder-type magnetic structure  72  is implanted. The internal magnetic structure  14  carries one or more magnets  18  having a polarity facing the airway that is the same as the rudder-type magnetic structure  72 . The rudder-type magnetic structure  72  magnetically interacts with the pharyngeal wall structure  14  by repelling. Forces of magnetic repulsion between the rudder-type structure  72  and the structure  14  in  FIG. 30  push the magnetic portion  74  of the tongue structure  72  anteriorly toward the mouth. This is because the magnets  16  of the structure  72  have an N-polarity facing the airway, and the magnets  18  of the structure  14  have the same N-polarity facing the airway, or vice versa. The rudder portion  76 , being essentially free of magnets, is not magnetically attracted, but remains implanted in tissue across the raphé on the other side of the tongue. As a result, the structure  72  will pivot about the rudder portion  76  away from the internal magnetic structure  14 . The additional surface area of the rudder portion  76  will push more tissue in the direction of the pivot, and will also serve as a tissue anchor that lends overall stability to the structure  72 . The magnetic interaction opens one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
     The rudder portion of a rudder-type magnetic structure  72  can be variously sized and configured. For example, as shown in FIGS.  31 A/B/C, the main body  78  of the structure  72  can include a rudder portion  76  having a surface area that is increased by providing an appendage  92  (see  FIGS. 31A and 31B ) that projects outward at a desired angle (e.g., 45° to 90°) from the rudder portion  76 . That is (see  FIGS. 31A and 31B ), given that the main body  78  of the structure lies along a longitudinal axis  84 , the axis  82  of the appendage  92  lies at an angle from the longitudinal axis  84 . The appendage  92  gives greater depth to the overall implant in the direction of the magnetic field. Generally, magnetic implants having greater depth apply more force to tissue, because of increased surface area and mass. Thus, the appendage  92  serves to apply more force and stability to the implant. Additionally, the appendage  92  may also carry embedded sources of magnetism, in which case the appendage would also lower the distance between magnetic structure  12  and an external magnetic structure  14  with which it magnetically interacts. 
     As  FIGS. 31C and 31D  show, the location of magnetic implant  72 , when implanted, is desirably centered with respect to the raphé, with the longitudinal axis  84  of the main body extending transversely of the raphé and the axis  82  of the rudder appendage  92  extending generally parallel to the raphé. As  FIG. 31C  shows, the implant  72  is divided into two parts by the raphé of the tongue. On one side  88  of the raphé, at least two magnets  16  are carried by the structure  70 . On the other side  86  of the raphé lies the rudder portion  76  with appendage  92 , which is desirably free or essentially free of magnetic material. As  FIG. 31D  shows, the portion  76  and its appendage  92  act as a rudder to help move more tongue tissue as a result of magnetic attraction and/or repulsion between the magnet-carrying side  88  of the implant and another magnetic structure of a type previously described. 
       FIGS. 32A and 32B  show an alternative embodiment of a rudder-type magnetic structure  98  sized and configured for placement in a tongue. In the embodiment, the rudder-type magnetic structure  98  comprises a main body  100  having a longitudinal axis  104 . The main body  100  comprises a first region  106  carrying a first array of one or more magnets  16 ( 1 ) and a second region  108  carrying a second array of one or more magnets  16 ( 2 ). As  FIGS. 32A and 32B  show, the polarity of the magnets in the first array  16 ( 1 ) is generally opposite to the polarity of the second array  16 ( 2 ). The main body  100  further comprises an intermediate rudder appendage  112  between the first and second regions  106  and  108  having an axis  102  that projects at an angle from the longitudinal axis  104 . The rudder appendage  112  is desirably free or essentially free of magnets. In the illustrated embodiment (see  FIGS. 32A and 32B ), the magnets of the first array  16 ( 1 ) have a N-polarity facing in the direction of the rudder appendage  112 , and the magnets of the second array  16 ( 2 ) have a S-polarity facing the direction of the rudder appendage  112 . 
       FIG. 33  shows a cross-section of a collapsed pharyngeal conduit, like  FIG. 3  but shown from another perspective, sufficient to cause an apneic episode.  FIG. 33  also shows the rudder-type structure  98  shown in FIGS.  32 A/B implanted in the tongue. As can be seen in  FIG. 33 , the main body  100  is implanted with its longitudinal axis  104  extending generally transversely of the raphé of the tongue, with the first region  106  located on one side of the raphé and the second region  108  located on the opposite side of the raphé. The rudder appendage  112  occupies the raphé between the first and second regions, and the axis  102  of the rudder appendage  112  extends generally parallel to the raphé. 
       FIG. 34A  shows a new position of the tongue (compared to  FIG. 33 ) due to the interactions between the rudder-type structure  98  shown in FIGS.  32 A/B and an external magnetic structure  14  of the type shown in FIGS.  12 C/E, which together form an embodiment of a Tongue System  10   a . The structure  14  carries magnets  18  having a polarity facing the oral cavity that are opposite to the polarities of the magnets of the second array  16 ( 2 ) and the same as the polarities of the magnets of the first array  16 ( 1 ). In the illustrated embodiment, the magnets  18  have a N-polarity facing the oral cavity. As a result, forces of magnetic attraction are generated between the structure  14  and the second array  16 ( 2 ), whereas forces of magnetic repulsion are generated between the structure  14  and the first array  16 ( 1 ). The attracting forces pull the second portion  108  of the structure  98  anteriorly toward the mouth, whereas the repelling forces push the first portion  106  of the structure  98  posteriorly toward the pharyngeal wall. The rudder appendage  112 , being essentially free of magnets, is not magnetically attracted or repelled, but remains implanted in tissue in the region of the raphé between the two opposite sides of the tongue. The rudder stabilizes the push and pull of the different magnetic interactions. The magnetic interactions open one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
       FIG. 34B  shows a new position of the tongue (compared to  FIG. 33 ) due to the interactions between the rudder-type structure shown in FIGS.  32 A/B and an external magnetic structure  14  of the type shown in  FIG. 12E , which form another embodiment of a Tongue System. The structure  14  carries magnets  18  on only the side of the tongue occupied by the first array  16 ( 1 ). The magnets  18  have a polarity facing the oral cavity that is the same as the polarities of the magnets of the first array  16 ( 1 ) and opposite to the polarities of the magnets of the second array  16 ( 2 ). The attracting forces pull the second portion  108  of the structure  98  toward the opposite side of the tongue, whereas the repelling forces push the first portion  106  of the structure posteriorly toward the pharyngeal wall. The rudder appendage  112 , being essentially free of magnets, is not magnetically attracted or repelled, but remains implanted in tissue in the region of the raphé between the two opposite sides of the tongue. As a result, the second portion  108  of the structure  98  will pivot toward the external magnetic structure  14 , as the first portion  106  of the structure  98  pivots away from the external magnetic structure  14 . The rudder appendage  112  stabilizes the push-and-pull of the different magnetic interactions, and will draw more tissue in the direction of the pivot. The magnetic interactions open one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
       FIG. 35  shows a new position of the tongue (compared to  FIG. 33 ) due to the interactions between the rudder-type structure shown in FIGS.  32 A/B and an internal magnetic structure  14  placed in or on the posterior pharyngeal wall across from the region of the tongue where the first array of the structure is implanted. The internal magnetic structure  14  carries one or more magnets  18  having a polarity facing the airway that is the same as the magnets in the second array  16 ( 2 ) and that is opposite to the magnets in the first array  16 ( 1 ). As a result, forces of magnetic repulsion are generated between the structure  14  and the second array  16 ( 2 ), whereas forces of magnetic attraction are generated between the structure  14  and the first array  16 ( 1 ). The repelling forces push the second portion  108  of the structure  98  toward the oral cavity, whereas the attracting forces pull the first portion  106  of the structure posteriorly toward the pharyngeal wall. The rudder appendage  112 , being essentially free of magnets, is not magnetically attracted or repelled, but remains implanted in tissue in the region of the raphé between the two opposite sides of the tongue. As a result, the second portion  108  of the structure  98  will pivot away from the internal magnetic structure  14 , as the first portion  106  of the structure  98  pivots toward the internal magnetic structure  14 . The rudder appendage  112  stabilizes the push-and-pull of the different magnetic interactions, and will draw tissue in the direction of the pivot. The magnetic interactions open one side of the pharyngeal airway, sufficient to prevent the apneic episode. 
     D. Ferromagnet With an Elastic Component 
     In an alternative embodiment, an implantable ferromagnetic structure  136  used in the tongue, soft palate, or pharyngeal wall can comprise ferromagnetic material  138  coupled to one or more elastic components  140 , as shown in  FIGS. 41A and 41B . The elastic component coupled to the ferromagnetic material  138  is sized and configured to deflect under load in a prescribed manner and to recover an initial shape when unloaded. As shown in  FIGS. 41A and 41B  the elastic component  140  comprises a spring. 
     The spring form of the elastic component  140  may vary. It may, e.g., comprise a helical tension or compression spring, in which wire is wrapped in a coil that resembles a screw thread, as shown in  FIG. 41A . Alternatively, the elastic component  140  may comprise a leaf spring, comprising plate elements secured. Still alternatively, the elastic component  140  may comprise a spiral spring made from flat strip or wire coiled about the ferromagnetic material  138 . Still alternatively, the elastic component  140  may comprise a torsion-bar spring. 
     The ferromagnetic material  138  desirably comprises one or more permanent magnets. The shape of the ferromagnetic material  138  need not be cylindrical, as shown in  FIG. 41A . Other sizes, shapes, and configurations can be used, including cubes, pyramids, tetrahedrons, and various polyhedrons. 
     As shown in  FIG. 41A , the elastic component  140  may be made out of metal or a polymer, desirably a rigid polymeric material. The elastic component  140  may consist of a single piece or comprise a construct of multiple elastic components. In spring form, the shape of the elastic component  140  need not be helical (as shown in  FIG. 41A ), but other constructions capable of deflecting under load can be used. The set up of a spring-form elastic component  140  could resemble a trampoline with multiple springs or elastic components attached peripherally about the ferromagnetic material  138 . The spring-form elastic component  140  can also be tuned to any amount of force needed by modifying the pitch, the number of turns, the thickness and the overall angle in the spring&#39;s “cone.” 
     As shown in  FIG. 41B , the configuration of the spring-form elastic component  140  makes possible its use as an anchor, capable of attaching the ferromagnetic material  138  into soft tissue, by twisting. The presence of the spring-form elastic component  140  can thus eliminate the need to use sutures for attachment of the structure  136  to soft tissue. The spring-form elastic component  140  can also be secured (e.g., like a bone screw) to a bone structure, and, in this arrangement, also serve as a tethering device for the ferromagnetic structure  138 . In whatever form, the elastic component  140  may be embedded or coated in a silicon matrix or soft material, as may be the ferromagnetic material  138 . The presence of the elastic component on the ferromagnetic structure  136  can help stabilize torque in a system that incorporates ferromagnetic implants. Stabilizing the torque can bring about more predictability in the ferromagnetic implants. 
     E. Alternative Embodiments to the Tongue, Soft Palate and Combined Systems 
     In certain cases, the above-described Tongue, Soft Palate, and Combined Systems may not provide enough attractive magnetic force to maintain a patent airway. Under these circumstances, the respective System desirably includes at least one additional structure that interactions to provide a magnetic force that complements the attractive magnetic force to maintain a patent airway. 
     1. Complementary Tongue System 
       FIGS. 4E and 4F  show alternative embodiments of the Tongue System that provide a complementary magnetic force to further resist the collapse of the tongue. In the representative embodiment shown in  FIGS. 4E and 4F , the magnetic structure  12  is positioned in or on the tongue, as previously described. More specifically, magnetic structure  12  can be positioned either in the anterior or in the posterior region of the tongue. In  FIG. 4E , the magnetic structure  14  (as previously described), which the magnetic structure  12  interacts with by attraction, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 4D , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). 
     Furthermore, as shown in  FIGS. 4E and 4F , to provide a complementary magnetic force for further resisting the collapse of the tongue, the Tongue System includes a magnetic structure  15  positioned in or on the posterior pharyngeal wall, generally opposite of magnetic structure  12  in or on the tongue. The magnetic structure  15  carries at least one magnetic material  19  that, by magnetic interactions with the structure  12 , generates a magnetic force that includes at least one vector or component that magnetically repels the structure  12  in or on the mobile tissue of the tongue away from the structure  15  in or on the relatively less mobile tissue of the pharyngeal wall. In the illustrated embodiment, the magnetic material  19  of the structure  15  has a polarity the same as the polarity of the magnetic structure  12  that it faces across the airway. The magnetic structure  15  thereby interacts with the magnetic structure  12  across the airway by repulsion. The repelling magnetic interaction between the magnetic structure  15  and the magnetic structure  12  in the posterior airway serves to stabilize the tongue and resist collapse of the tongue against the pharyngeal wall during sleep. The repelling magnetic interaction between structures  12  and  15  in the posterior airway complements the attracting magnetic interaction between the structures  12  and  14  in the anterior airway, which likewise serves to resist posterior or other movement of the tongue toward the posterior pharyngeal wall. The complementary magnetic forces prevent, in whole or in part, the occurrence of the airway-occluding tissue condition shown in  FIG. 3 . The magnetic force between the first and second ferromagnetic structures  12  and  14 , coupled with the magnetic force between ferromagnetic structures  12  and  15 , work together to keep the airway open (i.e., patent) during sleep. 
     2. Complementary Soft Palate System 
       FIGS. 5C and 5D  show alternative embodiments of the Soft Palate System that provide a complementary magnetic force to further resist the collapse of the soft palate/uvula. In the representative embodiment shown in  FIGS. 5C and 5D , the magnetic structure  12  is positioned in or on the soft palate/uvula, as previously described. In  FIG. 5C , the magnetic structure  14  (as also previously described), which the magnetic structure  12  interacts with by attraction, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 5D , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). 
     Furthermore, as shown in  FIGS. 5C and 5D , to provide a complementary magnetic force for further resisting the collapse of the soft palate/uvula, the Soft Palate System includes a magnetic structure  15  is positioned in or on the posterior pharyngeal wall, generally opposite of magnetic structure  12  in the soft palate/uvula. The magnetic structure  15  carries at least one magnetic material  19  that, by magnetic interactions with the structure  12 , generates a magnetic force that includes at least one vector or component that magnetically repels the structure  12  in or on the mobile tissue of the soft palate/uvula away from the structure  15  in or on the relatively less mobile tissue of the pharyngeal wall. In the illustrated embodiment, the magnetic material  19  of the structure  15  has a polarity the same as the polarity of the magnetic structure  12  it faces across the airway. The magnetic structure  15  thereby interacts with the magnetic structure  12  across the airway by repulsion. The repelling magnetic interaction between the magnetic structure  15  in or on the pharyngeal wall and the magnetic structure  12  in or on the soft palate/uvula serves to stabilize the soft palate/uvula and resist collapse of the soft palate/uvula against the pharyngeal wall during sleep. The repelling magnetic interaction between structures  12  and  15  in the posterior airway complements the attracting magnetic interaction between the structures  12  and  14  in the anterior airway, which likewise serves to resist posterior or other movement of the soft palate/uvula toward the posterior pharyngeal wall. The complementary magnetic forces prevent, in whole or in part, the occurrence of the airway-occluding tissue condition shown in  FIG. 3 . The magnetic force between the first and second ferromagnetic structures  12  and  14 , coupled with the magnetic force between ferromagnetic structures  12   a / 12   b  and  15   a / 15   b , work together to keep the airway open (i.e., patent) during sleep. 
     3. Complementary Combined System 
       FIGS. 6C and 6D  show alternative embodiments of the Combined System that provide a complementary magnetic force to further resist the collapse of the tongue and soft palate/uvula. In the representative embodiment shown in  FIGS. 6C and 6D , the magnetic structure  12   b  is positioned in or on the tongue, while magnetic structure  12   a  is positioned in or on the soft palate/uvula, as previously described. More specifically, magnetic structure  12   b  can be positioned either in the anterior or in the posterior region of the tongue. In  FIG. 6C , the magnetic structure  14  (also as previously described), which the magnetic structure  12   a  and  12   b  interacts with by attraction, is positioned outside the airway (e.g., on the chin), whereas in  FIG. 6D , the magnetic structure  14  is positioned within the airway (e.g., in the oral cavity). 
     Furthermore, as shown in  FIGS. 6C and 6D , to provide a complementary magnetic force for further resisting the collapse of the tongue and the soft palate/uvula, the Combined System includes a magnetic structure  15   a  and a magnetic structure  15   b . The magnetic structure  15   a  is positioned in or on the posterior pharyngeal wall, generally opposite of magnetic structure  12   a  in or on the soft palate/uvula. The magnetic structure  15   b  is positioned in or on the posterior pharyngeal wall generally opposite to the magnetic structure  12   b  in or on the tongue. Each structure  15   a  and  15   b  carries at least one magnetic material  19  that, by magnetic interactions with the associated structure, respectively  12   a  and  12   b , generates a magnetic force that includes at least one vector or component that magnetically repels the respective structure  12   a  and  12   b  in or on the mobile tissue of the soft palate/uvula or tongue away from the structure  15  in or on the relatively less mobile tissue of the pharyngeal wall. In the illustrated embodiment, the magnetic material  19  of the structure  15  has a polarity the same as the polarity of the magnetic structure, respectively  12   a  and  12   b , it faces across the airway. The magnetic structures  15   a  and  15   b  thereby interact with the magnetic structures, respectively  12   a  and  12   b  across the airway by repulsion. The repelling magnetic interaction between the magnetic structure  15   a  in or on the pharyngeal wall and the magnetic structure  12   a  in or on the soft palate/uvula serves to stabilize the soft palate/uvula and resist collapse of the soft palate/uvula against the pharyngeal wall during sleep. Likewise, the repelling magnetic interaction between the magnetic structure  15   b  in or on the pharyngeal wall and the magnetic structure  12   b  in or on the tongue serves to stabilize the tongue and resist collapse of the tongue against the pharyngeal wall during sleep. The repelling magnetic interactions between structures  12   a / 12   b  and  15   a / 15   b  in the posterior airway complements the attracting magnetic interaction between the structures  12   a / 12   b  and  14  in the anterior airway, which likewise serves to resist posterior or other movements of either the soft palate/uvula and/or the tongue against the posterior pharyngeal wall. The complementary magnetic forces prevent, in whole or in part, the occurrence of the airway-occluding tissue condition shown in  FIG. 3 . The magnetic force between the first and second ferromagnetic structures  12  and  14 , coupled with the magnetic force between ferromagnetic structures  12   a / 12   b  and  15   a / 15   b , work together to keep the airway open (i.e., patent) during sleep. 
     V. Forces Required to Maintain a Patent Airway 
     As  FIGS. 36 and 37  show in a diagrammatic way, for a given individual, that a magnitude can be assigned to a force required to maintain separation between tongue tissue ( FIG. 36 ) or soft palate/uvula tissue ( FIG. 37 ) from the posterior pharyngeal wall, to thereby resist the collapse of an airway during an apneic episode. This force, designated F-sep in  FIGS. 36 and 37  can be obtained by physical measurement of a given individual, or it can based upon measurements taken during a cadaver study, or it can be selected empirically based upon general anatomic considerations for a population of individuals, or a combination of these and other considerations. 
     For a given individual, a magnitude can also be assigned to a counterbalancing force (designated F-nat in  FIGS. 36 and 37 ), which represents the force exerted by natural muscular activity upon the tongue ( FIG. 36 ) or the soft palate/uvula ( FIG. 37 ), to enable swallowing, chewing, or speech during normal airway function. The force F-nat can be also obtained by physical measurement of a given individual, or it can be selected empirically based upon general anatomic considerations for a population of individuals, or a combination of these and other considerations. 
     As shown in  FIGS. 36 and 37 , the magnetic force (F-mag) that a given system  10  develops can be expressed as a function of F-sep and F-nat, or F-mag=f (F-sep, F-nat). The magnetic force can comprise an attracting force (i.e., a force in essentially an anterior-posterior direction between the tongue or soft palate/uvula and the attracting magnetic structure worn on the chin or neck or on teeth within the oral cavity), a repelling force (i.e., a force in essentially an anterior-posterior direction between repelling magnetic structures in the tongue and posterior pharyngeal wall), and/or a torquing force (i.e., a force or moment of a force that tends to rotate the tongue or soft palate/uvula about an axis), and/or decentering force (i.e., a force in essentially a lateral or side-to-side direction that tends to offset the tongue or soft palate/uvula left or right), or a combination of two or more of these forces. The magnetic force F-mag maintains a separation between the tongue and the posterior pharyngeal wall ( FIG. 36 ), or between the uvula and the posterior pharyngeal wall ( FIG. 37 ), or combinations thereof, depending upon the desired therapeutic effect. 
     The function desirably incorporates the premise that F-sep≦F-nat, such that F-nat can overcome F-sep to preserve normal airway function. In effect, F-nat is the upper limit for the amount of force used which, to achieve an effective OSA therapy, which F-sep should not exceed. The function also desirably incorporates the premise that F-mag≧F-sep, so that the desired separation between the tongue and the posterior pharyngeal wall is maintained. In the case of systems activated only during the night, F-nat will necessarily be larger in magnitude because the only activities that need to be able to continue during sleep are swallowing and coughing, which require more force than speaking. 
     The function resolves F-sep and F-nat to provide an optimal therapeutic force that, at night, resists collapse of the tongue or soft palate/uvula against the pharyngeal wall during sleep, yet does not affect speech, swallowing or drinking during normal activities when the system is activated. 
     The function also desirably includes a tolerance factor ΔTol, which takes into account that F-nat can increase with time after implantation, as an individual develops tolerance to F-mag. F-nat can thereby increase with time after implantation, as the individual trains himself or herself to exert more force during swallowing or speech in the presence of F-mag to maintain normal airway function. The nature of the tolerance factor ΔTol can be ascertained by physical measurement of a given individual, or it can be selected empirically based upon general anatomic considerations for a population of individuals, or a combination of these and other considerations. 
     Further, in arriving at the absolute magnitude of F-sep for the tongue (whether relative to the pharyngeal wall, or uvula, or both), it has been discovered that F-sep for the tongue can have two components. The first component is the desired therapeutic force F(z) that is developed in an anterior-to-posterior direction, which prevents the tongue from falling back upon the posterior pharyngeal wall or uvula. The second component is an undesired decentralizing side loading force F(y) that can be exerted due to magnetic force discontinuities at the edges of the tongue implant. It has been observed that, as the edges of a magnetic tongue implant start to misalign with the other magnetic structure (on the chin or neck or on the teeth or in the uvula), the magnets at the edges of the tongue implant may start to twist in an attempt to orient themselves to a more desired attracting arrangement. This can cause the tongue implant to twist or flip. The decentralizing side loading force F(y) is an outcome of these edge discontinuities, which moves the tongue laterally, i.e., to the side (the soft palate/uvula, being anatomically anchored on three of four sides, is significantly more resistant to a side loading force than the tongue, which is anchored essentially only on the posterior side). 
     A desired therapeutic force magnitude F(z) can, if the edge discontinuities are not moderated, undesirably move the tongue laterally. The magnitude of the edge discontinuities, i.e., the magnitude of F(y), can be titrated and controlled by the design of the other magnetic structure, e.g., by directing the magnetic fields of the posterior and middle regions of the structure at an angle relative to the direction of the magnetic fields of the anterior region, as shown in FIGS.  16 A/B. Further, by stabilizing the tongue implant in the manners previously described, e.g., by the presence of a rudder as shown in  FIGS. 28 to 35  or by the use of mobile magnets as shown in  FIGS. 21 to 23 , the destabilizing effects of F(y) can be also counteracted. 
     An implant force&#39;scaling strategy like that shown in  FIG. 38  can be based upon an appreciation of these considerations. In  FIG. 38 , the magnitude of a force applied in an anterior-posterior direction upon the tongue necessary to achieve the desired therapeutic effect (i.e., F-sep) is indicated at A. As indicated before, this is the force required to separate tongue tissue from the posterior pharyngeal wall or uvula, or both, to thereby resist the collapse of an airway during an apneic episode. The force F-sep (also shown in  FIG. 36 ), can be obtained by physical measurement or selected empirically based upon general anatomic considerations for a population of individuals, or a combination of these and other considerations. 
     In  FIG. 38 , the magnitude of the resistance (F-res) of a given tongue decentered medially in response to an external side load is indicated at B. The specific magnitude of F-res can be obtained by physical measurement of a given individual, or it can be based upon cadaver studies, or it can be selected empirically based upon general anatomic considerations for a population of individuals, or a combination of these and other considerations. In  FIG. 38 , the magnitude of F-res (B) is expressed as a percentage of F-sep (A). That is, on the y-axis, F-sep (A) is expressed as 100% and F-res (B) is expressed as 60%. The particular relationship between F-sep and F-res can vary based upon anatomic considerations. 
     In  FIG. 38 , the magnitude of the anterior-to-posterior force F(z) generated by a given attracting magnetic structure (on the chin or neck or on the teeth or in the uvula, or combinations thereof) is indicated by C. As  FIG. 38  shows by the slope of C, this magnitude of F(z) will vary as a function of distance between the attracting magnetic structure and the tongue implant, as well as a function of the particular structural characteristics and stabilization of the tongue implant itself. 
     In  FIG. 38 , the magnitude of the side load force F(y) generated by the given pharyngeal wall implant is indicated by D. The slope and magnitude of D will vary based upon the design of the pharyngeal wall implant or the uvula implant, particularly with respect to the moderation of edge discontinuities, as previously described. The slope and magnitude of D will also depend upon the particular structural characteristics and stabilization of the tongue implant itself. 
     For a given magnetic force system affecting the tongue, the magnitude of F(z) with respect to the magnitude of F(y) represents an Implant Scaling Factor (F-scale). F-scale can be expressed as a ratio of F(z) to F(y); that is F-scale=F(z)/F(y). The magnitude of F-scale for a given magnetic force system affecting the tongue indicates that the system is likely to achieve the desired therapeutic effect without decentering the tongue. 
     It has been discovered that, for a given magnetic force system affecting the tongue, an F-scale≧1 is desirable. For a given magnetic force system affecting the tongue, an F-scale&lt;1 indicates that decentering of the tongue will occur, which offsets the desired therapeutic effect. An F-scale&lt;1 indicates that the edge discontinuities of the attracting magnetic structure (on the chin or neck or on the teeth) should be reduced or moderated and/or means for stabilizing the tongue implant are warranted. 
       FIG. 38  also lends itself to an implant force scaling strategy. The intersections of C and D with A and B define an optimal operating region E for a magnetic force system affecting the tongue. In region E, F(z) is at or above the magnitude that achieves the desired therapeutic effect but where F(y) is not at the magnitude at which side loading (i.e., decentering of the tongue) will occur. 
     Experimentally, it has been determined that the force F-mag likely required to keep an airway open on a cadaver using a magnetic force system that affects the tongue is no more than 1000 g. It is believed that magnetic tongue implant systems require a force of about 2 to about 750 g to maintain a patent airway. More specifically, a force in the range of about 5 to about 600 g is believed to provide the desired therapeutic benefits in combination with control of edge discontinuities in the other magnetic structure on chin or neck or on the teeth and stabilization of the tongue implant itself. 
     It is also believed that F-mag for a magnetic force system that affects the palate should also be no more than 1000 g. More specifically, for a magnetic force system that affects the palate, it is believed that a force F-mag of about 3 to about 800 g will provide therapeutic benefits without adversely affecting normal functioning of the airway. 
     VI. Conclusion 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     The above-described embodiments of this invention are merely descriptive of its principles and are not to be limited. The scope of this invention instead shall be determined from the scope of the following claims, including their equivalents.