protoplasm - Dictionary Definition : Vocabulary.com Random Word protoplasm Protoplasm is the gooey stuff that living cells are made of. A cell's protoplasm is colorless and surrounded by a plasma membrane. Sometimes people use protoplasm to mean “formless blob of life.” There are many elements that make up the protoplasm of a cell, including the nucleus, amino acids, lipids, and ions. Scientists generally use the word protoplasm to mean the cytoplasm plus the nucleus. It was coined in the 1840s by a German scientist, from the Greek roots proto, "first," and plasma, "something molded or formed." Continuous membrane | definition of continuous membrane by Medical dictionary Continuous membrane | definition of continuous membrane by Medical dictionary membrane [mem´brān] a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ. adj., adj mem´branous. alveolar-capillary membrane (alveolocapillary membrane) a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries. Called also blood-air barrier and blood-gas barrier .

arachnoid membrane arachnoid . basement membrane a sheet of amorphous extracellular material upon which the basal surfaces of epithelial cells rest; it is also associated with muscle cells, Schwann cells, fat cells, and capillaries, interposed between the cellular elements and the underlying connective tissue. It comprises two layers, the basal lamina and the reticular lamina , and is composed of Type IV collagen (which is unique to basement membranes), laminin, fibronectin, and heparan sulfate proteoglycans. basilar membrane the lower boundary of the scala media of the ear. Bowman's membrane a thin layer of basement membrane between the outer layer of stratified epithelium and the substantia propria of the cornea. Bruch's membrane the inner layer of the choroid, separating it from the pigmented layer of the retina. cell membrane plasma membrane . decidual m's (deciduous m's) decidua . Descemet's membrane the posterior lining membrane of the cornea; it is a thin hyaline membrane between the substantia propria and the endothelial layer of the cornea.

diphtheritic membrane the peculiar false membrane characteristic of diphtheria, formed by coagulation necrosis. drum membrane tympanic membrane . epiretinal membrane a pathologic membrane partially covering the surface of the retina, probably originating chiefly from the retinal pigment epithelial and glial cells; membranes peripheral to the macula are generally asymptomatic, while those involving the macula or adjacent to it may cause reduction in vision, visual distortion, and diplopia. extraembryonic m's those that protect the embryo or fetus and provide for its nutrition, respiration, and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua, and placenta. Called also fetal membranes . false membrane a membranous exudate, such as the diphtheritic membrane ; called also neomembrane . fenestrated membrane one of the perforated elastic sheets of the tunica intima and tunica media of arteries. fetal m's extraembryonic membranes .

hemodialyzer membrane the semipermeable membrane that filters the blood in a hemodialyzer , commonly made of cuprophane, cellulose acetate, polyacrylonitrile, polymethyl methacrylate, or polysulfone. Henle's membrane fenestrated membrane . high efficiency membrane a hemodialyzer membrane that has clearance characteristics that increase progressively with increases in dialysis blood flow rates; this usually implies that the membrane is not a high flux membrane . high flux membrane a hemodialyzer membrane that has a high permeability to fluids and solutes and thus a high rate of clearance of fluids and solutes composed of large molecules. hyaline membrane 3. a homogeneous eosinophilic membrane lining alveolar ducts and alveoli, frequently found at autopsy of infants that were preterm. See also hyaline membrane disease . hyoglossal membrane a fibrous lamina connecting the undersurface of the tongue with the hyoid bone. impaired oral mucous membrane a nursing diagnosis approved by the North American Nursing Diagnosis Association, defined as disruptions of the lips and soft tissue of the oral cavity.

Changes in the integrity and health of the oral mucous membrane can occur as a characteristic of such medical disorders as periodontal disease, uncontrolled diabetes mellitus, oral cancer, and infection with herpes. Chemical irritants such as alcohol and tobacco can also adversely affect the oral mucous membrane, as can mechanical trauma due to broken teeth, poorly fitting dentures, and endotracheal intubation. Other etiologic factors include dehydration, mouth breathing, poor oral hygiene, radiation to the head or neck, and antineoplastic agents. Preventive measures that can help maintain the health and integrity of the oral mucosa will depend on the cause. Routinely brushing and flossing the teeth during the day and at bedtime can help avoid dental caries and periodontal disease. Some patients may need instruction in the proper procedure for cleaning the teeth and removing debris and plaque, or they may need assistance in devising ways to cope with physical disabilities that make good oral hygiene difficult for them. Patients who are unconscious or unable to perform self-care activities should have mouth care as often as needed to keep the mouth clean and moist and avoid aspiration of debris and infectious microorganisms.

Adequate hydration and a lip lubricant can help avoid alterations in the oral mucosa and promote comfort. limiting membrane one that constitutes the border of some tissue or structure. mucous membrane the membrane covered with epithelium that lines the tubular organs of the body. olfactory membrane the olfactory portion of the mucous membrane lining the nasal fossa. placental membrane the membrane that separates the fetal from the maternal blood in the placenta. plasma membrane the membrane that encloses a cell; it is composed of phospholipids, glycolipids, cholesterol, and proteins. The primary structure is a lipid bilayer. Phospholipid molecules have an electrically charged “head” that attracts water and a hydrocarbon “tail” that repels water; they line up side by side in two opposing layers with their heads on the inner or outer surface of the membrane and their tails in the core, from which water is excluded. The other lipids affect the structural properties of the membrane. Proteins embedded in the membrane transport specific molecules across the membrane, act as hormone receptors, or perform other functions. Reissner's membrane the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.

membrane of round window secondary tympanic membrane. Scarpa's membrane tympanic membrane, secondary . semipermeable membrane one permitting passage through it of some but not all substances. serous membrane the membrane lining the walls of the body cavities and enclosing the contained organs; it consists of mesothelium lying upon a connective tissue layer and it secretes a watery fluid. synovial membrane the inner of the two layers of the articular capsule of a synovial joint; composed of loose connective tissue and having a free smooth surface that lines the joint cavity. tympanic membrane see tympanic membrane . tympanic membrane, secondary the membrane enclosing the round window ; called also Scarpa's membrane . unit membrane the trilaminar structure of all cellular membranes (such as the plasma membrane, nuclear membranes, mitochondrial membranes, endoplasmic reticulum, lysosomes) as they appear in electron micrographs. The biochemical structure is a lipid bilayer. vitelline membrane the external envelope of an ovum . vitreous membrane 4. a delicate boundary layer investing the vitreous body . mem·brane (mem'brān), 1.

A thin sheet or layer of pliable tissue, serving as a covering or envelope of a part, as the lining of a cavity, as a partition or septum, or as a connection of two structures. Synonym(s): membrana [TA] [L. membrana, a skin or membrane that covers parts of the body, fr. membrum, a member] membrane /mem·brane/ (mem´brān) a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ. alveolar-capillary membrane , alveolocapillary membrane a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries. Called also blood-air barrier and blood-gas barrier . alveolodental membrane periodontium . arachnoid membrane arachnoid (2). atlantooccipital membrane either of two midline ligamentous structures, one (the anterior ) passing from the anterior arch of the atlas to the anterior margin of the foramen magnum, and the other (the posterior ) connecting the posterior aspects of the same structures.

basement membrane a sheet of amorphous extracellular material upon which the basal surfaces of epithelial cells rest; it is also associated with muscle cells, Schwann cells, fat cells, and capillaries, interposed between the cellular elements and the underlying connective layer. Basement membrane, comprising the basal lamina and reticular lamina, in a diagram of a section through epithelial tissue. basilar membrane of cochlear duct lamina basilaris . Bichat's membrane fenestrated m. Bowman's membrane a thin layer of cornea between the outer layer of stratified epithelium and the substantia propria. Bruch's membrane the inner layer of the choroid, separating it from the pigmentary layer of the retina. Brunn's membrane the epithelium of the olfactory region of the nose. cloacal membrane the thin temporary barrier between the embryonic hindgut and the exterior. Corti's membrane a gelatinous mass resting on the organ of Corti, connected with the hairs of the hair cells. croupous membrane the false membrane of true croup. cytoplasmic membrane plasma m. decidual membranes , deciduous membranes decidua .

Descemet's membrane a thin hyaline membrane between the substantia propria and endothelial layer of the cornea. diphtheritic membrane a false membrane characteristic of diphtheria, formed by coagulation necrosis. elastic membrane one made up largely of elastic fibers. enamel membrane 1. dental cuticle . 2. the inner layer of cells within the enamel organ of the fetal dental germ. epiretinal membrane a pathologic membrane partially covering the surface of the retina, probably originating chiefly from the retinal pigment epithelial and glial cells. extraembryonic membranes those that protect the embryo or fetus and provide for its nutrition, respiration, and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua, and placenta. false membrane neomembrane; a membranous exudate, such as the diphtheritic membrane. fenestrated membrane one of the perforated elastic sheets of the tunica intima and tunica media of arteries. germinal membrane blastoderm . glomerular membrane the membrane covering a glomerular capillary.

hemodialyzer membrane the semipermeable membrane that filters the blood in a hemodialyzer , commonly made of cuprophane, cellulose acetate, polyacrylonitrile, or polymethyl methacrylate. hyaline membrane 1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle. 2. a layer of eosinophilic hyaline material lining alveoli, alveolar ducts, and bronchioles, found at autopsy in infants who have died of respiratory distress syndrome of the newborn. hyaloid membrane vitreous m. (1). Jackson's membrane a web of adhesions sometimes covering the cecum and causing obstruction of the bowel. peridental membrane , periodontal membrane periodontal ligament . placental membrane the membrane separating the fetal from the maternal blood in the placenta; sometimes inappropriately called the placental barrier . Placental membrane separating the blood in the fetal capillaries from the maternal blood in the intervillous space.

(A), chorionic villus containing the fetal vessels and surrounded by maternal blood in the intervillous space; (B), cross-section through a villus, showing the layers of the placental membrane separating the fetal blood from the maternal blood surrounding the villus. plasma membrane the structure, composed of lipids, proteins, and some carbohydrates, that encloses the cytoplasm of a cell, forming a selectively permeable barrier. pupillary membrane a mesodermal layer attached to the rim or front of the iris during embryonic development. Reissner's membrane the thin anterior wall of the cochlear duct, separating it from the scala vestibuli. reticular membrane , reticulated membrane a netlike membrane over the spiral organ of the ear, through which pass the free ends of the outer hair cells. schneiderian membrane the mucous membrane lining the nose. secondary tympanic membrane the membrane enclosing the fenestra cochlearis. serous membrane tunica serosa . Shrapnell's membrane the thin upper part of the tympanic membrane. suprapleural membrane the strengthened portion of the endothoracic fascia attached to the inner part of the first rib and the transverse process of the seventh cervical vertebra.

synaptic membrane the part of the plasma membrane of a neuron that is within a synapse. synovial membrane 1. the inner of the two layers of the articular capsule of a synovial joint, composed of loose connective tissue and having a free smooth surface that lines the joint cavity. 2. either of two membranes, superior and inferior, lining the articular capsule of the temporomandibular joint. tympanic membrane the thin partition between the external acoustic meatus and the middle ear. Tympanic membrane (membrana tympanica). undulating membrane a protoplasmic membrane running like a fin along the bodies of certain protozoa. unit membrane the trilaminar structure of the plasma membrane and other cellular membranes (e.g., nuclear m's, mitochondrial m's) revealed by the electron microscope. vestibular membrane of cochlear duct the thin anterior wall of the cochlear duct, separating it from the scala tympani. vitelline membrane the cytoplasmic, noncellular membrane surrounding an oocyte . vitreous membrane n. 1. Biology a. A thin, pliable layer of tissue covering surfaces or separating or connecting regions, structures, or organs of a living organism.

b. A semipermeable layer that bounds a cell or an organelle, typically consisting of lipids and proteins. 2. Chemistry A thin sheet of natural or synthetic material that is permeable to substances in solution. mem′bra·nal (-brə-nəl) adj. membrane [mem′brān] Etymology: L, membrana, thin skin a thin layer of tissue composed of epithelial cells and connective tissue that covers a surface, lines a cavity, or divides a space in the body. The principal kinds of membranes are mucous membrane, serous membrane, skin, and synovial membrane . membrane Anatomy A thin layer of tissue covering a surface, lining a body cavity or dividing a space or organ. Molecular biology (1) A phospholipid mono- or bilayer which forms a hydrophobic barrier around and within cells. (2) A sheet of nylon, nitrocellulose or similar material used to create a template for a gel for Southern blots, Northern blots or Western blots. Obstetrics A popular term for the amniotic sac, see there.

membrane A very thin layer of tissue covering a surface, lining a body cavity, or dividing a space or organ mem·brane (mem'brān) 1. A thin sheet or layer of pliable tissue, serving as a covering or envelope, the lining of a cavity, a partition or septum, or a connection between two structures. membrane (mem'bran?) [L. membrana, parchment] 1. A thin, pliable layer of tissue that lines a tube or cavity, covers an organ or structure, or separates one part from another. 2. A very thin sheet of polymer, ceramics, glass, or metal. ALVEOLOCAPILLARY MEMBRANE alveolocapillary membrane The structures and substances through which gases must pass as they diffuse from air to blood (oxygen) or blood to air (carbon dioxide), including the alveolar fluid and surfactant, cell of the alveolar wall, interstitial space (tissue fluid), and cell of the capillary wall. Synonym: respiratory membrane See: illustration alveolodental membrane Periodontium.

arachnoid membrane The delicate middle membrane of the three meninges, which enclose the brain and spinal cord. The arachnoid membrane is 5–6 cells thick. It adheres to the inner surface of the dura and is connected to the pia by a spiderweb of thin connections. Thee space between the arachnoid and pia (the subdural space) is filled with cerebrospinal fluid. Synonym: arachnoid ; arachnoid mater atlanto-occipital membrane A single midline ligamentous structure that extends from the arch of the atlas to the borders of the foramen magnum. basement membrane A two-part extracellular layer found at the interface between some tissues, e.g., skin and dermis. . The basement membrane is made of a basal lamina along the cell surfaces, coated by a stronger collagen-rich layer, the reticular lamina basilar membrane The membrane extending from the tympanic lip of the osseous spiral lamina to the crest of the spiral ligament in the cochlea of the ear. It separates the tympanic canal from the cochlear duct and supports the organ of Corti. See: illus.

under organ of Corti black membrane An artificially constructed membrane made of lipids arranged in a bilayer. Bowman membrane See: Bruch, Karl buccopharyngeal membrane In the embryo, the membrane that separates the oral cavity from the foregut until the fourth week of development. Synonym: pharyngeal membrane cell membrane The membrane that forms the outer boundary of a cell; it is made of phospholipids, protein, and cholesterol, with carbohydrates on the outer surface. Synonym: plasma membrane illustration The dense fascia between the pectoralis minor and subclavius muscles. cricothyroid membrane The membrane connecting the thyroid and cricoid cartilages of the larynx. croupous membrane The fibrinous false membrane on the mucous surfaces in diphtheria. dural membrane Dura mater. egg membrane Any of the protective membranes or envelopes enclosing an ovum. It may be primary (formed by egg itself, as in vitelline membrane), secondary (formed by follicle cells, as in zona pellucida), or tertiary (formed by oviduct or uterus, as in albumin and shell of hen's egg).

elastic membrane Any of several membranes formed of elastic connective tissue fibers. enamel membrane 2. The thin internal layer of cells of the enamel organ. epiretinal membrane An excessive proliferation of retinal pigment epithelial cells and extracellular proteins on the retinal surface. This condition, which can distort vision, is typically found in people older than 50. Marked visual blurring caused by epiretinal membranes occurs in macular pucker. See: macular pucker external limiting membrane 1. The outer layer of cells of the embryonic neural tube. 2. The membrane in the retina of the eye through which the receptor portions of the rods and cones protrude. false membrane Fibrinous exudate on a mucous surface of a membrane, as in croup or diphtheria. Synonym: croupous membrane fenestrated membrane A layer of elastic connective tissue possessing minute round or oval openings. It is found in the tunica intima and tunica media of medium-sized and large arteries. fetal membrane Any of the membranous structures that protect and support the embryo and provide its nutrition, respiration, and excretion.

The structures are yolk sac, allantois, amnion, chorion, decidua, and placenta. fibrous membrane A membrane composed entirely of fibrous connective tissue. Examples include the fasciae, aponeuroses, perichondrium, periosteum, dura mater, and the capsules of some organs. glassy membrane 1. The transparent capsule that separates membrana granulosa from the theca of the graafian follicle. 2. The internal layer of a hair follicle separating the epithelial and connective tissues. glial cell membrane An extremely delicate membrane, formed of foot plates of astrocytes, that surrounds all the blood vessels in the brain, spinal cord, and the lining of the pia mater, separating these vessels from the nervous tissue proper. This membrane is thought to be one of the components of the blood-brain barrier. homogeneous membrane A fine membrane covering villi of the placenta. Huxley membrane The membrane between the outer root sheath of a hair follicle and the inner fibrous layer. hyaloid membrane The membrane that envelops the vitreous humor. hyoglossal membrane A transverse fibrous membrane uniting tongue to hyoid bone.

internal limiting membrane 1. The inner layer of ependymal cells lining the embryonic neural tube. 2. The glial membrane forming the innermost layer of the retina and the iris. interosseous membrane 1. A fibrous membrane in the arm connecting ulna to radius. 2. A fibrous membrane in the leg connecting tibia to fibula. laryngeal mucous membrane The mucous membrane, glands, and cilia that characterize the lining of the larynx. lingual mucous membrane The mucosa covering the tongue. masticatory mucous membrane The mucosa of the mouth involved in the masticatory process. It is characterized by a keratinized surface epithelium, and includes the hard palate, gingiva, and dorsum of the tongue. medullary membrane Endosteum. mucous membrane Any of the membranes that line passages and cavities communicating with the air, consisting of epithelium, a basement membrane, and an underlying layer of connective tissue (lamina propria). Mucus-secreting cells or glands are usually present in the epithelium but may be absent. In humans, mucous membranes and the skin prevent the entry of pathogens.

Mucous membranes are normally colonized with nonpathogenic organisms that discourage colonization by pathogens because the resident organisms compete for the nutrients essential to their survival. Some mucosal surfaces in the digestive tract have special characteristics that tend to repel or kill organisms, such as the extremely high acid level on the mucosa of the stomach. Noninvasive examination of membranes should reveal the degree of moisture, cyanosis, pallor, hyperemia, pigmentation, lesions or their absence, and hemorrhage. Pallor is seen in all anemias. If the pallor is temporary, it may indicate shock or vasomotor spasm, or it may occur in severe hemorrhages. Blanching and flushing alternately accompany aortic regurgitation. Hyperemia of the mucous membranes is indicative of certain pathological changes in particular tissues, e, g., of the buccal mucous membrane, due to decayed teeth, traumatism, or stomatitis; of the nasal mucosa, due to ulceration of the nose, rhinitis, or inflammation; of the eyes (local irritation), due to a foreign body, ulcer, inflammation.

Dryness is seen in fevers, chronic gastritis, some liver disturbances, excitement, shock, prostration, fatigue, thirst, and certain drugs. nasal mucous membrane The mucosa lining the nasal cavity and characterized by pseudostratified ciliated columnar epithelium with goblet cells. Nasmyth membrane See: Nasmyth membrane nictitating membrane A third eyelid present in lower vertebrates and represented in humans by a fold of the conjunctiva, the plica semilunaris. nuclear membrane The two-layered membrane surrounding the chromosomes of a cell. The membrane has pores and its outer layer is continuous with the endoplasmic reticulum of the cell. A fibrous membrane closing the obturator foramen. olfactory membrane The membrane in the upper part of the nasal cavity that contains olfactory receptors. oral membrane A double epithelial layer separating the nasal pits from the embryonic oral cavity. otolithic membrane A layer of gelatinous substance containing otoconia or otoliths, found on the surface of maculae in the inner ear. palatal mucous membrane The lining of the mouth on the hard and soft palates.

The hard palate has heavily keratinized epithelium and copious mucous glands or fat in the submucosa. The mobile soft palate contains muscle in addition to mucous glands, and is much less keratinized on the surface. peridental membrane An obsolete term for the periodontal ligament. periodontal membrane Buccopharyngeal membrane. pharyngeal mucous membrane The lining of the pharynx. The mucosa of the nasopharynx is pseudostratified ciliated epithelium; the mucosa of the oropharynx and laryngopharynx is stratified squamous epithelium. pial membrane The membrane of the placenta that separates the maternal blood from fetal blood. plasma membrane A membrane resembling a serous membrane but differing in structure as the endothelium. pupillary membrane The transparent membrane closing the fetal pupil. If it persists after birth, it is called persistent pupillary membrane. pyogenic membrane The granular lining of an abscess or fistula. pyophylactic membrane The lining membrane of an abscess cavity separating it from healthy tissue.

quadrangular membrane The upper portion of the elastic membrane of the larynx extending from the aryepiglottic folds to the level of the ventricular folds below. Reissner membrane Alveolocapillary membrane. reticular membrane The membrane formed by the cuticular plates of the distal ends of supporting cells in the organ of Corti. Ruysch membrane See: Schwann, Theodore selectively permeable membrane A membrane that allows one substance, such as water, to pass through more readily than another, such as salt or sugar. semipermeable membrane See: osmosis serous membrane A membrane consisting of mesothelium lying on a thin layer of connective tissue that lines the closed cavities (peritoneal, pleural, and pericardial) of the body and is reflected over the organs in the cavity. Serous fluid, similar to lymph, decreases friction between the two layers. Shrapnell membrane See: submucosa. synovial membrane The membrane lining the capsule of a joint and secreting synovial fluid. The synovial membrane is pink, smooth, and shiny and is made of an intima lining a stronger, vascular fibrous membrane.

The intima contains synoviocytes (fibroblast- and macrophage-like cells), which remove debris from the synovial fluid and synthesize some of the mucin (specifically, hyaluronic acid) of the synovial fluid. Most of the synovial fluid is filtered from the blood vessels of the outer fibrous layer of the synovial membrane. Synonym: synovium tectorial membrane The thin, jelly-like membrane projecting from the vestibular lip of the osseous spiral lamina and overlying the spiral organ of Corti of the ear. thyrohyoid membrane The membrane joining the hyoid bone and the thyroid cartilage. tympanic membrane The three-layered membrane at the inner (medial) end of the external auditory canal, forming the lateral boundary of the middle ear cavity. The outer layer of the tympanic membrane is keratinized skin, continuous with the skin lining the external ear canal. Synonym: drum ; eardrum unit membrane The phospholipid bilayer first described as the typical cell membrane, then as the membrane of intracellular structures. vapor-permeable membrane A membrane, usually transparent, that is permeable to oxygen and water vapor.

It may be prepared with an adhesive backing that will stick only to dry skin. This type of membrane has been used in covering wounds. The membrane must be applied properly without wrinkles and changed as often as necessary to prevent excess accumulation of fluid and bacteria under it. vestibular membrane The membrane in the cochlea of the inner ear that separates the cochlear duct from the vestibular canal. vestibular mucous membrane The mucosa of the oral vestibule with its nonkeratinized stratified squamous epithelium, elastic lamina propria, and seromucous labial glands. virginal membrane An obsolete term for the hymen. vitelline membrane The membrane that forms the surface layer of an ovum. Synonym: yolk membrane; zona pellucida vitreous membrane 1. The inner membrane of the choroid. 2. The innermost layer of the connective tissue sheath surrounding a hair follicle. Wachendorf membrane a thin sheet of tissue. membrane covering/envelope or lining basement membrane thin layer of fibrocellular tissue between epithelial and connective tissues; e.g.

at dermoepidermal junction synovial membrane connective tissue membrane lining joint cavities and bursae; gives rise to synovial fluid membrane A thin layer of tissue which covers a surface, separates cellular structures or organs, or connects adjacent structures. basement membrane of the corneal epithelium A very thin non-cellular layer adjacent to Bowman's layer and upon which the columnar basal cells of the corneal epithelium are bound by hemidesmosomes. Bowman's membrane See Bowman's layer . Bruch's membrane Thin (about 1.5 μm), shiny, non-vascular layer of the choroid located on the inner side next to the retinal pigment epithelium. It consists of two contiguous layers; the inner one called the lamina vitrea (or basement membrane of the pigment epithelium) and the outer one called the lamina elastica. See angioid streaks . Descemet's membrane Strong, resistant, thin (about 8 μm) layer of the cornea located between the endothelium (from which it is secreted) and the stroma. It is practically the last corneal structure to succumb to disease processes and it can regenerate after injury. Syn.

lamina elastica posterior; posterior limiting layer. See descemetocele ; Kayser- Fleischer ring. Elschnig's inner limiting membrane A thin layer of astrocytes covering the optic disc. It is in continuity with the inner limiting membrane of the retina. In some cases this layer is thickened in the central part of the disc to form the central meniscus of Kuhnt. It is transparent and not usually visible with the ophthalmoscope. hyaloid membrane This is not really a membrane, but a concentration of cells and fibres enclosing the vitreous body. intermuscular membrane A thin, elastic membrane originating from the muscle sheath of each rectus muscle and connecting it to the neighbouring rectus muscle. The membrane fuses with the capsule of each muscle, as well as with Tenon's capsule. nictitating membrane A fold of the conjunctival mucous membrane that can be drawn over part or all of the cornea in a winking-like action to clean and lubricate the cornea. It is present in many birds, reptiles, fishes and some mammals and is normally hidden in the inner canthus. Syn. third eyelid. See plica semilunaris .

membrane of the retina, external limiting This layer has the form of a wire netting through which pass the processes of the rods and cones of the retina. It is located between the latter and the outer nuclear layer. It is believed to be formed by the fibres of Mueller. See Mueller's cell. membrane of the retina, internal limiting Glass-like membrane lying between the retina and the vitreous body and forming a boundary for both. For that reason it has sometimes also been considered to be the hyaloid membrane of the vitreous. The feet of the fibres of Mueller are attached to this membrane but do not form it. Syn. internal limiting layer of the retina. See Mueller's cell. n a thin layer of tissue that covers a surface or divides a space or organ. membrane, barrier, n small pieces of meshlike material inserted between the gingival tissue flap and underlying bone, primarily during flap surgery. It is used to prevent grafted material from moving and to stop harmful cells from growing. It can be used alone or in combination with bone grafting. membrane, basement, n the delicate, PAS-positive, noncellular membrane on which the epithelium is seated. membrane bone, n See bone, membrane.

membrane, collagen, n a bioabsorbable, semipermeable membrane made of collagen. It is hemostatic, chemotactic, and well tolerated by adjacent tissue. (in´trəmem´brənus), n formed by differentiation of mesenchymal cells into osteoblasts and bone matrix. See also bone, membrane and bone, membrane, formation. membrane, mucous, n See membrane, barrier. (ôr´ōfərin´jēəl), n a layer of tissue on the cephalic end of the embryo in the region where the oral cavity will later be formed. Previously called buccopharyngeal membrane. See also oropharynx. membrane, periodontal, n See ligament, periodontal . membrane, subimplant, n the fibrous connective tissue that regenerates from the periosteum and that forms between the inner surface of the implant framework and the bone surface. membrane a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.

alveolocapillary membrane a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries. membrane-attack complex complement components C5-C9 which form in terminal stage of either of the complement pathways and lead to cell lysis. basilar membrane the lower boundary of the scala media of the ear. Bowman's membrane a thin layer of basement membrane between the outer layer of stratified epithelium and the substantia propria of the cornea. Bruch's membrane the inner layer of the choroid, separating it from the pigmented layer of the retina. membrane carrier a mechanism in the cell membrane of epithelial cells in the intestinal mucosa which facilitates the rapid transport of for example glucose, into the cell and thus into the bloodstream. cell membrane see channel . continuous membrane the middle of the three membranes on the outside of the yolk of the hen egg. cricothyroid membrane the membrane connecting the thyroid cartilage to the cricoid cartilage. It is extensive in the horse and surgical incision through it allows access to the interior of the larynx.

Descemet's membrane the posterior lining membrane of the cornea; it is a thin hyaline membrane between the substantia propria and the endothelial layer of the cornea. drum membrane tympanic membrane (below). extraembryonic m's those that protect the embryo or fetus and provide for its nutrition, respiration and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua and placenta . extravitelline membrane the outermost of the three membranes on the outside of the yolk of the hen egg. false membrane a membrane similar to the pseudomembrane; fibrinous exudates readily loosened from underlying tissue, as in croupous or pseudomembranous inflammation. fenestrated membrane one of the perforated elastic sheets of the tunica intima and tunica media of arteries. fetal m's see fetal membranes. See also extraembryonic membranes (above). fibrous membrane the strong, fibrous support layer in a joint capsule. Henle's membrane see henle's membrane. hyaline membrane the olfactory portion of the mucous membrane lining the nasal fossa. periodontal membrane see periodontium .

perivitelline membrane the innermost of the three layers on the outside of the yolk in the hen egg. placental membrane the membrane that separates the fetal from the maternal blood in the placenta. plasma membrane the membrane that encloses a cell; it is composed of phospholipids, glycolipids, cholesterol and proteins. The primary structure is a lipid bilayer. Phospholipid molecules have an electrically charged 'head' that attracts water and a hydrocarbon 'tail' that repels water; they line up side by side in two opposing layers, with their heads on the inner or outer surface of the membrane and their tails in the core, from which water is excluded. The other lipids affect the structural properties of the membrane. Proteins embedded in the membrane transport specific molecules across the membrane, act as hormone receptors, or perform other functions. membrane potential of a cell is the voltage difference across the cell membrane resulting from the differential concentrations of sodium and potassium on either side of the membrane. The resting potential, for example in a nerve cell, is altered by the temporary opening of the sodium channels in the membrane during an action potential, allowing a redistribution of the ions.

membrane proteins the large number of proteins attached to a cell membrane. They include integral proteins, called also intrinsic, which are embedded in the phospholipid bi-layer of the cell membrane, and peripheral proteins, called also extrinsic, because they are loosely bound and can readily be extracted without damage to the cell membrane. pupillary membrane a vascular membrane which occupies the pupil in the embryo stage, completely covering the anterior surface of the lens but subsequently disappears. See also persistent pupillary membrane. Reissner's membrane the thin anterior wall of the cochlear duct, separating it from the scala vestibuli. Scarpa's membrane transport of electrolytes across semipermeable membranes with the aid of a transporter. unit membrane the trilaminar structure of all cellular membranes (such as the plasma membrane, nuclear membranes, mitochondrial membranes, endoplasmic reticulum, lysosomes) as they appear in electron micrographs. The biochemical structure is a lipid bilayer. wing membrane the membrane comprising the wing of the bat. yolk membrane the membrane investing the yolk of the hen egg; it includes (from the inside out) the perivitelline, the continuous and the extravitelline membranes. Patient discussion about membrane Q.

HYALINE MEMBRANE DISEASE in pre-mature infants;what are the causes of it in pregnant women? A. the cause of Hyaline Membrane disease is pre-mature birth. while the fetus develop, about in the 29th week a substance called surfactant is created in the lungs. this substance's function is to change the surface tension of the fluid in the lungs- therefore decreasing it's force. the surface tension tends to shrink the lungs and can cause the lungs to collapse. so a premature baby wouldn't be able to breath properly. Q. For those that had an epimacular membrane removed, how long was it before your eye healed? How was your vision afterwards? Do you now require or benefit from glasses? A. Epimacular membrane removal can be associated with a variety of ocular conditions and therefore the healing process varies tremendously depending on the underlying pathology. Furthermore, this condition may recur. Cell membrane - definition of cell membrane by The Free Dictionary Cell membrane - definition of cell membrane by The Free Dictionary Related to cell membrane: nucleus , mitochondrion , Cell membrane transport cell membrane n. The semipermeable membrane that encloses the cytoplasm of a cell.

Also called cytomembrane, plasmalemma, plasma membrane. cell membrane n (Biology) a very thin membrane, composed of lipids and protein, that surrounds the cytoplasm of a cell and controls the passage of substances into and out of the cell. Also called: plasmalemma or plasma membrane cell′ mem`brane the semipermeable membrane enclosing the cytoplasm of a cell. [1865–70] cell membrane The thin membrane that forms the outer surface of the protoplasm of a cell and regulates the passage of materials in and out of the cell. It is made up of proteins and lipids. cell membrane

Question: What is a word for the living content of a cell that is surrounded by a plasma membrane?
Answer: Protoplasm