Patent Publication Number: US-2021186482-A1

Title: Systems, devices, and related methods for retracting tissue

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of Ser. No. 15/669,005, filed Aug. 4, 2017, which claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application 62/371,471, filed on Aug. 5, 2016, all of which applications are incorporated herein by reference in their entireties for all purposes. 
    
    
     TECHNICAL FIELD 
     Various aspects of the present disclosure relate generally to tissue retraction. More specifically, the present disclosure relates to systems, devices, and related methods for retracting tissue. 
     BACKGROUND 
     Technological developments have given users of medical systems, devices, and methods the ability to conduct increasingly complex procedures on subjects. The removal of tissue in, for example, a subject&#39;s gastrointestinal tract, is a type of procedure in which difficulties may arise. One such area of difficulty involves removing a lesion on tissue. In order to remove the lesion, the user may retract tissue at or around the lesion. This retraction may enable the user to clearly observe a cutting plane for removing the lesion. Having this visualization may aid in preventing unwanted incision errors, such as severing vessels. The visualization also may aid in ensuring that as much of or all of the lesion is removed. 
     In order to achieve retraction, the user may inject a solution into tissue at or around the lesion to elevate the tissue in preparation for cutting. Reaching and elevating the lesion, and in particular, the base of the lesion, may require making a multitude of injections. This may be time consuming. Moreover, the injections may not provide sufficient tissue retraction to provide the line of sight, or other access, desired by the user. These potential problems are exacerbated when the lesion targeted for removal is a flat lesion. 
     Solutions that offer retraction, while reducing or eliminating the occurrence of the above-described drawbacks, may lead to better outcomes for users and subjects. 
     SUMMARY 
     Aspects of the disclosure relate to, among other things, systems, devices, and methods for retracting tissue. Each of the aspects disclosed herein may include one or more of the features described in connection with any of the other disclosed aspects. 
     In one aspect of the present disclosure, a tissue retraction system may include a first anchor, a second anchor, and an elongate coupling member extending between the first anchor and the second anchor. The system also may include a holder for receiving the first anchor, the second anchor, and the elongate coupling element. The holder may include a proximal portion and a distal portion. The distal portion may have a smaller width than the proximal portion such that the distal portion exerts a force on a proximal end of the first anchor during deployment of the first anchor from the holder. The force may move the first anchor into an open configuration for receiving tissue. 
     Aspects of the tissue retractions system may include one or more of the features below. The first anchor may abut the second anchor in the holder. The first anchor may include a first jaw and a second jaw, and the first jaw may be pivotably attached to the second jaw. The first anchor may further include a biasing element that biases at least one of the first jaw and the second jaw to move toward the other of the first jaw and the second jaw. The second anchor may include a third jaw and a fourth jaw, and the third jaw may be pivotably attached to the fourth jaw. Distal ends of the third jaw and the fourth jaw may engage opposing surfaces of proximal ends of the first jaw and the second jaw in the holder. 
     In another aspect of the present disclosure, a redeployable clip system for tissue may include a clip. The clip may include a fastening element having a first configuration for receiving tissue, and a second configuration for engaging tissue. The clip also may include a base for receiving at least a portion of the fastening element. The fastening element may move to the first configuration when moved away from the base, and the fastening element may move to the second configuration when moving toward the base. The clip also may include an actuation element at least partially received within the base for moving the fastening element between the first configuration and the second configuration. The actuation element may include an engagement element. The system also may include an instrument. The instrument may include a manipulation element for engaging the engagement element. The instrument also may include a receiver for receiving at least a portion of the base to fix the base relative to the receiver. The manipulation element may be configured to position the base for fixing relative to the receiver. Moving the actuation element relative to the base when the base is fixed on the receiver may move the fastening element between the first configuration and the second configuration. 
     Aspects of the redeployable clip system may include one or more of the features below. The receiver may include a first coupling element. The base may include a second coupling element. The first coupling element may releasably couple to the second coupling element to fix the base relative to the receiver. The first coupling element may include one of a groove and a protrusion configured for receipt in the groove. The second coupling element may include the other of the groove and the protrusion. The first coupling element may include internal geometric features. The second coupling element may include external geometric features that mate with the internal geometric features. The first coupling element and the second coupling element may form a snap-fit connection. The manipulation element may include an arm having a bent distal end and the engagement element may include a loop. The manipulation element may include a ball and the engagement element may include a socket. The ball may be releasably coupled to the socket. 
     In yet another aspect of the present disclosure, a method for retracting tissue may include anchoring a first element to tissue at a first location. The method also may include anchoring a second element to tissue at a second location. The second location may be spaced from the first location. The anchoring of the second element to the tissue may cause tension to build in a portion of a coupling element that extends between the first element and the second element, such that the first element, the coupling element, and the second element may exert a force on the tissue at the first location. The force may have a direction of application and a magnitude. The method also may include manipulating the tissue at the first location while the force is exerted on the tissue at the first location. 
     Aspects of the method for retracting tissue may include one or more of the features below. Releasing the second element from the tissue at the second location. Moving the second element toward tissue at a third location, the third location being spaced from the second location. Anchoring the second element to the tissue at the third location. Adjusting the magnitude of the force by drawing the first element toward the second element using the coupling element. Ejecting the first element from a holder. Engaging the first element with the holder to move the first element to an open configuration to receive the tissue at the first location. Disengaging the first element from the holder to move the first element to a closed configuration to anchor the first element to the tissue at the first location. 
     It may be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary aspects of the present disclosure and together with the description, serve to explain the principles of the disclosure. 
         FIGS. 1A-1H  show a retraction system in use, in accordance with aspects of the present disclosure. 
         FIG. 2  shows another retraction system in use, in accordance with aspects of the present disclosure. 
         FIGS. 3A-3E  show yet another retraction system in use, in accordance with aspects of the present disclosure. 
         FIGS. 3F-3I  show a holder and anchors of the retraction system of  FIGS. 3A-3E , in accordance with aspects of the present disclosure. 
         FIG. 4  shows a cutaway view of an assembly including a holder, anchors, and a pusher, in accordance with aspects of the present disclosure. 
         FIG. 5  shows a cutaway view of another assembly including a holder, anchors, and a pusher, in accordance with aspects of the present disclosure. 
         FIG. 6  shows exemplary engagement elements and fasteners arranged in columns, in accordance with aspects of the present disclosure. 
         FIGS. 7A-7C  show another retraction system in use, in accordance with aspects of the present disclosure. 
         FIG. 8  shows an anchor, in accordance with aspects of the present disclosure. 
         FIG. 9  shows another anchor, in accordance with aspects of the present disclosure. 
         FIG. 10  is an end view of another holder, in accordance with aspects of the present disclosure. 
         FIG. 11  shows a cutaway view of a holder and anchors, in accordance with aspects of the present disclosure. 
         FIGS. 12A-12F  show another retraction system in use, in accordance with aspects of the present disclosure. 
         FIG. 13  shows portions of a positioning instrument and an anchor, in accordance with aspects of the present disclosure. 
         FIG. 14  shows portions of another positioning instrument and another anchor, in accordance with aspects of the present disclosure. 
         FIG. 15  shows portions of another positioning instrument and another anchor, in accordance with aspects of the present disclosure. 
         FIGS. 16A and 16B  show portions of another positioning instrument and another anchor, in accordance with aspects of the present disclosure. 
         FIG. 17  shows a perspective view of a portion of another anchor, in accordance with aspects of the present disclosure. 
         FIG. 18  shows portions of another positioning instrument and another anchor, in accordance with aspects of the present disclosure. 
         FIGS. 19A-19H  show another retraction system in use, in accordance with aspects of the present disclosure. 
         FIGS. 20A and 20B  show another version of the retraction system of  FIGS. 19A-19H  in use, in accordance with aspects of the present disclosure. 
         FIGS. 21A and 21B  show another version of the retraction system of  FIGS. 19A-19H  in use, in accordance with aspects of the present disclosure. 
         FIG. 22  shows an auxiliary anchor, in accordance with aspects of the present disclosure. 
         FIGS. 23A and 23B  show another version of the retraction system of  FIGS. 19A-19H  in use, in accordance with aspects of the present disclosure. 
         FIGS. 24A and 24B  show another version of the retraction system of  FIGS. 19A-19H  in use, in accordance with aspects of the present disclosure. 
         FIGS. 25A and 25B  show another version of the retraction system of  FIGS. 19A-19H  in use, in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is drawn to systems, devices, and methods for retracting tissue. Reference will now be made in detail to aspects of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same or similar reference numbers will be used through the drawings to refer to the same or like parts. The term “distal” refers to a portion farthest away from a user when introducing a device into a patient. By contrast, the term “proximal” refers to a portion closest to the user when placing the device into the patient. The term “retraction” may refer, for example, to positioning tissue to expose and/or visualize a cutting plane for removing the tissue. As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term “exemplary” is used in the sense of “example,” rather than “ideal.” 
       FIGS. 1A-1H  show a system  100  for retracting a portion of tissue  102 . Tissue  102  may include, for example, an area  104  targeted for removal, such as an area with a lesion. System  100  may include an introducer  106  for providing access to tissue  102 . Introducer  106  may deploy anchors  108  and  110  into portions of tissue  102  opposing, or otherwise facing, target area  104 . Additionally or alternatively, introducer may deploy anchors  108  and  110  into portions of tissue spaced apart from target area  104 .  FIGS. 1A and 1B  show anchors  108  and  110  being deployed. 
     Introducer  106  also may deploy an anchor  112  into target area  104 , as shown in  FIG. 1C . A tether  114 , visible in  FIG. 1D , may be coupled to anchor  112 . A clip  116  may be coupled to tether  114 . Introducer  106  and a positioning instrument (not visible in  FIG. 1D ) therein may attach clip  116  to anchor  108  to retract target area  104 . A cutting instrument  120 , shown in  FIG. 1E , may be used to cut the retracted target area  104 . 
       FIGS. 1F and 1G  show introducer  106  and positioning instrument  118  removing clip  116  from anchor  108 , and attaching clip  116  to anchor  110 , to further retract target area  104 . Anchors  108  and  110  may act as staged pull points for retracting target area  104 . The space between anchors  108  and  110  may provide a user with the ability to implement different vectors of retraction (e.g., directions and/or magnitudes of retraction) for retracting target area  104 . This control over the vector of retraction may provide the user with an enhanced ability to expose and/or visualize the cutting plane the user will use to guide cutting of target area  104  with cutting instrument  120 .  FIG. 1H  shows cutting instrument  120  cutting the retracted target area  104  after adjustment of the retraction vector. 
     Introducer  106  may include an elongate tubular member  122 . Elongate tubular member  122  may include lumens (not shown) that extend lengthwise through the interior of elongate tubular member  122 . The lumens may receive one or more of an instrument, a lighting element (not shown), an imaging element (not shown), and/or a flow of fluid or other material (not shown) entering into or exiting from target area  104 . 
     An end cap  126  may cover the distal end of elongate tubular member  122 . End cap  126  may include ports  128  that communicate with the lumens (see, for example,  FIGS. 1F and 1H ). A port  130  may communicate with the instrument lumen. An instrument inserted through the instrument lumen may extend out of the distal end of introducer  106  via port  130 . The other ports  128  may communicate with the other lumens to receive the lighting element, imaging element, and/or flow of fluid or other material. A user of introducer  106  may use the lighting element and the imaging element to visualize target area  104  and its surroundings. Introducer  106  may include, for example, any suitable type of endoscope, sheath, or catheter. 
     Introducer  106  also may include a handle (not shown) having a steering mechanism (not shown) mounted thereon. The steering mechanism may be coupled to one or more steering wires or cables that may extend lengthwise through elongate tubular member  122 . By manipulating the steering mechanism to exert tension and/or compression forces on the steering wires or cables, the user may control deflection of the distal end of introducer  106 . 
     Anchor  108  may include a first end  132  (abutting tissue  102  in  FIG. 1A ) configured to penetrate into tissue  102 . First end  132  may include, for example, a sharp penetrating tip. Anchor  108  also may include a second end  134  (visible in  FIGS. 1B-1H ) opposite first end  132 . Second end  134  may serve as an attachment point. For example, second end  134  may include a loop, eyelet, hook, or any other suitable attachment element. 
     The intermediate portion of anchor  108  between first end  132  and second end  134  may move between a contracted or rest configuration and an extended or stretched configuration. When stretched, anchor  108  may exert a biasing force that tends to bring first end  132  and second end  134  toward each other. For example, the intermediate portion of anchor  108  may include a helical tension spring  136 . 
     Helical tension spring  136  also may offer functionality in addition to providing the biasing force. For example, rotating helical tension spring  136  in one of a clockwise direction and a counterclockwise direction may facilitate penetration of first end  132  deeper into tissue  102 , similar to operation of a corkscrew. Rotating helical tension spring  136  in the other of the clockwise direction and the counterclockwise direction may facilitate moving first end  132  back out of tissue  102 . This may provide the user with the ability to control the depth of penetration of anchor  108  into tissue  102 . 
     Anchor  110  may include one or more of the features of anchor  108 . In one example, anchor  110  may be identical to anchor  108 . Anchor  110 , however, may be deployed into tissue  102  at a position spaced apart from anchor  108 . As will be explained in detail below, due to the spacing of anchors  108  and  110 , anchors  108  and  110  may act as staged pull points that impart different vectors of retraction onto target area  104 . 
     Anchor  112  also may include or more of the features of anchor  108 . For example, anchor  112  may include a first end  138  configured to penetrate tissue at target area  104  (as seen in  FIG. 1C ), a second end  140  opposite first end  138 , and a helical tension spring  142  connecting first end  138  to second end  140  (a seen in  FIGS. 1D-1H ). In one example, a length of anchor  112  may be greater than a length of anchor  110 . The depth of penetration of anchor  112  in target area  104  may be controlled by rotating anchor  112  in either of the clockwise and counterclockwise directions. 
     Tether  114  may include a wire, a cord, a cable, an elastic band (e.g., a rubber band), a spring (e.g., a helical tension spring), a suture, a high carbon spring wire, a braided or wound filament, stainless steel, nitinol, spring steel, music wire, muscle wire, and/or any other suitable elongate member. Tether  114  may be metallic, polymeric, or a combination of metallic and polymeric. One end of tether  114  may be attached to second end  140  of anchor  112  (as seen in  FIGS. 1D-1H ). The other end of tether  114  may be attached to clip  116 . Clip  116  may include a base element  144 . One end of base element  144  may be attached to an engagement element  146 . Engagement element  146  may be configured to releasably couple to the second ends of anchors  108  and  110 . Tether  114  may attach to clip  116  where base element  144  meets engagement element  146 . Alternatively, tether  114  may attach to clip  116  at any other suitable location on clip  116 . 
     An outer surface of base element  144  may include a shoulder or abutment  148  thereon. Shoulder  148  may include one or more protrusions protruding from the outer surface. Shoulder  148  may engage anchor  112 , as described below. In an example where tether  114  includes a helical tension spring, tether  114  may be integral with helical tension spring  142  of anchor  112 . 
     An end of base element  144 , opposite the end attached to engagement element  146 , may include an opening (not shown). The opening may receive a tip portion  150  of a positioning instrument  118 , permitting receipt of tip portion  150  within base element  144  such that clip  116  may move with tip portion  150 .  FIG. 1F  shows tip portion  150  prior to its insertion into base element  144 , and  FIG. 1G  shows tip portion  150  within base element  144  (with tip portion  150  being obscured by base element  144 ). A shaft portion (not shown) of positioning instrument  118  may extend proximally through the instrument lumen. The user may manipulate the shaft portion to extend and retract tip portion  150  out of and into introducer  106 , respectively, and/or to otherwise move tip portion  150 . The shaft portion may be flexible enough to deflect with introducer  106  when introducer  106  is deflected by the user. 
     Prior to being deployed, positioning instrument  118 , anchors  108 ,  110 , and  112 , and tether  114  may be housed within the instrument lumen. This may, for example, prevent anchors  108 ,  110 , and  112  from prematurely engaging tissue as the distal end of introducer  106  navigates towards target area  104 . In the instrument lumen, tip portion  150  of positioning instrument  118  may be received within base element  144  of clip  116 . Anchor  112  may surround clip  116 . Second end  140  of anchor  112  may engage shoulder  148 . First end  138  of anchor  112  may engage the second end of anchor  110 . The first end of anchor  110  may engage second end  134  of anchor  108 . First end  132  of anchor  108  may be recessed from port  130 . 
     Once the distal end of introducer  106  is positioned relative to target area  104 , the user may deflect the distal end of introducer  106  in preparation for deploying anchor  108  into tissue  102 . Deploying anchor  108  may include moving positioning instrument  118  distally to extend at least first end  132  of anchor  108  out of port  130  and into contact with tissue  102  ( FIG. 1A ). Deploying anchor  108  also may include rotating positioning instrument  118  about its central longitudinal axis. This rotation may rotate clip  116 , anchor  112 , anchor  110 , and anchor  108 , through the chain of engagement between these elements. As first end  132  of anchor  108  rotates, first end  132  may penetrate into tissue  102 , and may burrow deeper into tissue  102  with continued rotation. When the desired depth of penetration is reached, positioning instrument  118  and introducer  106  may be moved away from anchor  108 , leaving anchor  108  in place in tissue  102 . Anchor  110  may be deployed into tissue  102  in a similar manner at another position (see  FIG. 1B ). Anchor  112  also may be deployed into target area  104  in a similar manner (see  FIG. 1C ). 
     Positioning instrument  118 , and clip  116  mounted thereon, may move further and further distally during deployment and release of anchors  108 ,  110 , and  112 . By the time anchor  112  is being deployed, engagement element  146  may extend distally out of the instrument lumen and port  130 , as shown in  FIG. 1C . With first end  138  of anchor  112  embedded in target area  104 , the user may move introducer  106 , positioning instrument  118 , and clip  116  (whose base element  144  may still be mounted on tip portion  150  of positioning instrument  118 ) toward anchor  108 . This movement may impart a tensile force on tether  114 , which may pull anchor  112  and target area  104 . The retraction may be along a vector extending between target area  104  and anchor  108 . The movement also may stretch anchors  108  and  112 , and/or tether  114 . 
     With anchors  108 ,  110 , and  112 ; tether  114 ; and clip  116  deployed, positioning instrument  118  may be withdrawn from the instrument lumen to allow insertion of cutting instrument  120 . Cutting instrument  120  may be guided distally through the instrument lumen, and extended distally out of port  130  to the position shown in  FIG. 1E . Cutting instrument  120  may include a distal cutting element  154 . Cutting element  154  may include, for example, a blade, an electrosurgical electrode, a heating element, and/or any other element suitable for cutting tissue  102 . A shaft  156  may extend proximally from cutting element  154 , through the instrument lumen, and to the proximal end of introducer  106 . Shaft  156  may be operatively coupled to a power source, such as an electrosurgical unit or other suitable power source, to provide the energy for cutting tissue  102 . Alternatively, positioning instrument  118  may be left in place, and cutting instrument  120  may be introduced through another lumen. 
     The user may remove target area  104  by sweeping the distal end of introducer  106  back-and-forth, thereby sweeping cutting element  154  back-and-forth across the retracted target area  104  (as indicated by the two-headed arrow near cutting element  154  in  FIG. 1E ). Other movements of cutting element  154 , including stabbing, twisting, lifting, lowering, and the like, may also be performed. As cutting element  154  cuts target area  104 , target area  104  may form a flap that may be drawn toward anchor  108  by tension and/or biasing forces in anchor  112 , tether  114 , and/or anchor  108 . This may lead to a reduction in the retraction force exerted on target area  104 . In order to increase the retraction force, the user may withdraw cutting instrument  120  from the instrument lumen. The user may reintroduce positioning instrument  118  into the instrument lumen, and navigate positioning instrument  118  until tip portion  150  once again extends distally out of port  130 , as depicted in  FIG. 1F . Tip portion  150  may re-enter base element  144  of clip  116 . Tip portion  150 , with the assistance of introducer  106 , may move clip  116  to release engagement element  146  from second end  134  of anchor  108 . Tip portion  150  and introducer  106  then may move clip  116  to bring engagement element  146  into engagement with the second end of anchor  110 , as seen in  FIG. 1G . This movement may impart a tensile force on tether  114 , which may pull anchor  112 , and thereby further retract target area  104 . The retraction may be along a vector extending between target area  104  and anchor  110 . The movement of clip  116  to anchor  110  also may stretch anchors  110 ,  112 , and/or tether  114 . 
     Positioning instrument  118  may once again be withdrawn from the instrument lumen to make room for cutting instrument  120 . The user may continue cutting the retracted target area  104  using cutting instrument  120 , as shown in  FIG. 1H . Alternatively, positioning instrument  118  and cutting instrument  120  may be positioned in different lumens of introducer  106 , and one need not be withdrawn to make way for the other. It should be understood that additional anchors may have been deployed into tissue  102  along with anchors  108  and  110 , allowing the user to further retract target area  104  to assist with cutting. The process steps described above may be repeated until target area  104  is removed. 
       FIG. 2  shows another system  200  for retracting tissue  202  at a target area or lesion  204 . Like system  100 , system  200  may include an introducer  206 , a cutting instrument  220 , anchors  208  and  210  for embedding into tissue  202  to act as staged pull points, an anchor  212  for embedding in target area  204 , a tether  214  for linking anchor  212  to anchors  208  and  210 , and a clip  216  at an end of tether  214  for engaging anchors  208  and  210 . 
     System  200  may differ from system  100  in a variety of ways. For example, anchor  208  may include a base element  244  having a fastener (not shown) attached to a first end. The fastener may be embedded into tissue  202  to secure anchor  208  to tissue  202 . The fastener may include, for example, a helical penetrating end similar to anchor  108 . An engagement element  234  may be attached to a second end of base element  244 . Engagement element  234  may include a loop or eyelet. Anchor  210  may be similar to, or even identical to, anchor  208 . 
     Anchor  212  may include a base element  242  having a fastener  238  at a first end, and tether  214  at a second end  240 . Fastener  238  may include, for example, a grasping element formed by jaws. It is contemplated that the jaws may move between an open position for receiving tissue and a closed position for grasping the received tissue. The fasteners of anchors  208  and  210  also may be similar to fastener  238 . Any suitable positioning instrument (not shown) may be configured to actuate the jaws between the open position and the closed position. Exemplary positioning instruments are described below. Alternatively, a positioning instrument similar to positioning instrument  118  of system  100  may be used to deploy anchors  208 ,  210 , and  212 ; tether  214 ; and clip  216  from introducer  206 . 
     A first end of tether  214  may be attached to second end  240  of anchor  212 . A second end of tether  214  may be attached to clip  216 . Clip  216  may include an engagement element  246  configured for receipt in engagement element  234  of anchor  208  (and the engagement element of anchor  210 ) to attach clip  216  to anchor  208 . Clip  216  also may include an aperture or eyelet  258  configured to receive cutting instrument  220 . 
     Any suitable positioning instrument may be used to deploy anchors  208 ,  210 , and  212 ; tether  214 ; and clip  216  from within an instrument lumen of introducer  206 . With anchors  208 ,  210 , and  212 ; tether  214 ; and clip  216  deployed, and the positioning instrument withdrawn from the instrument lumen, cutting instrument  120  may be guided distally through the instrument lumen and extended distally out of introducer  206 . Alternatively, the positioning instrument and cutting instrument  120  may occupy different lumens of introducer  206 , and one need not be removed to make way for the other. 
     The user may insert the distal end of cutting instrument  220  into aperture  258  of clip  216 . Using movement of introducer  206  and cutting instrument  220 , the user may pull clip  216  toward anchor  208  (shown in dashed line in  FIG. 2 ). The user may attach engagement element  246  of clip  216  to engagement element  234  of anchor  208 . These movements may impart a tensile force on tether  214 , which may pull anchor  212 , and thereby retract target area  204 . The retraction may be along a vector extending between target area  204  and anchor  208 . The movement also may stretch tether  214 . 
     With target area  204  retracted, the user may sweep a cutting element  254  of cutting instrument  220  across the retracted target area  204 . As cutting element  254  cuts target area  204 , target area  204  may form a flap that may be drawn toward anchor  208  by tension and/or biasing forces in tether  114 . This may lead to a reduction in the retraction force on target area  204 . In order to increase the retraction force, the user may reinsert cutting instrument  220  into aperture  258  of clip  216 . The user may move clip  216 , using cutting instrument  220  and introducer  206 , to release engagement element  246  from engagement element  234  of anchor  108 . Cutting instrument  220  then may move clip  216  to bring engagement element  246  into engagement with the engagement element of anchor  210  (shown in solid line in  FIG. 2 ). This movement may impart a tensile force on tether  214 , which may pull anchor  212 , and thereby further retract target area  204 . The retraction may be along a vector extending between target area  204  and anchor  210 . The movement also may stretch tether  214 . 
     The user may cut the further-retracted target area  204  using cutting instrument  220 . It should be understood that additional anchors may have been deployed into tissue  202  along with anchors  208  and  210 , allowing the user to further retract target area  204  to assist with cutting, by executing the above-described steps. The process may be repeated until target area  204  is removed. 
     It should be understood that aspects of system  200  may be used interchangeably with aspects of system  100 . For example, one or more of anchors  208 ,  210 , and  212 ; tether  214 ; and clip  216  of system  200  may be used in place of anchors  108 ,  110 , and  112 ; tether  114 ; and clip  116  of system  100 . The opposite also is contemplated. That is, one or more of anchors  108 ,  110 , and  112 ; tether  114 ; and clip  116  of system  100  may be used in place of anchors  208 ,  210 , and  212 ; tether  213 ; and clip  216  of system  200 . 
       FIGS. 3A-3I  show another system  300  for retracting tissue.  FIGS. 3A-3E  show system  300  in use in a subject.  FIGS. 3F-3I  show a portion of system  300  being used, to more clearly show certain aspects of system  300 . System  300  may include an introducer  306  (similar to introducer  106 ) for deploying anchors  308  and  310  into tissue  302  to act as staged pull points. Prior to deployment, anchors  308  and  310  may be received in a lumen  360  of a holder  362  (the lumen being shown in  FIGS. 3F-3I ). Holder  362  may be slidable within an instrument lumen (not shown) of introducer  306 , such that the user may retract holder  362  into the instrument lumen during navigation of introducer  306  to a target area, and extend holder  362  out of the distal end of introducer  306  to facilitate deployment of anchors  308  and  310  into tissue  302 . While within lumen  360 , anchors  308  and  310  may be constrained by the surfaces of holder  362  that form lumen  360  (see  FIGS. 3F-3I ). For example, anchors  308  and  310  may be held in a straightened configuration by the interior surfaces of holder  362 . 
     Anchors  308  and  310  may be serially arranged in lumen  360 . A first end  332  of anchor  308  may extend toward the distal end of holder  362 . A second end  334  of anchor  308  may engage a first end of anchor  310 , as seen in  FIG. 3H . In one example, anchor  308  may be integral with anchor  310 , with anchors  308  and  310  being connected by a frangible portion. Alternatively, anchors  308  and  310  may be discrete segments, with second end  334  of anchor  308  abutting the first end of anchor  310 . 
     The second end of anchor  310  may engage a distal end of a pusher or plunger  364 . The user may move pusher  364  distally to push anchors  308  and  310  distally through lumen  360 . With continued distal movement, pusher  364  may cause first end  332  of anchor  308  to extend out of holder  362 . First end  332  may penetrate tissue  302  (see  FIGS. 3A, 3B, and 3F ). As more of anchor  308  extends out of holder, the exposed portion of anchor  308  may begin returning to its unconstrained configuration (see  FIGS. 3C, 3G, and 3H ). The unconstrained configuration may include, for example, the loop configuration shown in  FIGS. 3D, 3E, and 3I , or alternatively, a triangle, a hook, a staple, or any other suitable shape. Anchor  308  may be made of any suitable material, including wire, stainless steel, nitinol, high carbon spring steel, a polymeric material that includes shape memory, and/or bio-absorbable materials. Once anchor  308  is freed from holder  362 , it may separate from anchor  310  and remain on tissue  302  (see  FIGS. 3D and 3I ). The first end of anchor  310  may extend out of holder  362 , and the deployment process may repeat for deploying anchor  310  at a location spaced apart from anchor  308  ( FIG. 3E and 3I ). While two anchors  308  and  310  are depicted, it should be understood that any number of anchors may be received in holder  362  depending on how many staged pulling points the user wants to set. 
       FIG. 4  shows another holder  462 . Holder  462  may be similar to holder  362  of system  300 , except anchors  408  and  410 , along with any additional anchors, may be stacked. Anchors  408  and  410  may partially overlap, instead of being arranged end-to-end like anchors  308  and  310 . A lumen  460  of holder  462  may be wider than lumen  360  of holder  362  to accommodate the stacked anchors  408  and  410 . A plunger or pusher  464 , similar to plunger or pusher  364  of system  300 , may push a proximal end  434  of anchor  408  distally to deploy anchor  408  into tissue. Plunger  464  may then retract and move to engage a proximal end of anchor  410  in preparation for deploying anchor  410 . This process may be repeated to deploy all of the anchors in holder  462 . 
       FIG. 5  shows a holder  562 . Holder  562  may be similar to holders  362  and  462  of systems  300  and  400 , respectively. In holder  562 , anchors  508  and  510 , along with any other anchors, may be arranged side-by-side in a bundle formation within a lumen or chamber  560 . A plunger or pusher  564 , similar to plunger or pushers  364  and  464  of systems  300  and  400 , respectively, may push proximal ends of the anchors distally, one at a time, to deploy the anchors into tissue. Between deployments, plunger  564  may be retracted and positioned at a proximal end of the next anchor in preparation for deployment of the next anchor. 
       FIG. 6  shows an arrangement or table  668  having three columns  670 ,  672 , and  674 . Column  670  shows various types of engagement elements including, for example, a single hook  673  having a sharp end, a grasping element  674  with jaws, a multi-hook assembly  676  with sharp ends, a magnet  678 , a first half  680  of a hook-and-loop fastener, a hook  682  with a bulbous end, and a loop  684 . Any of the engagement members in column  670  may be used in systems  100  and  200 , in place of engagement elements  146  and  246  of clips  116  and  216 , respectively. 
     Column  672  shows various types of engagement elements that may engage the engagement elements of column  670 . Column  672  includes, for example, a loop or eyelet  686  (configured to attach to single hook  673 , grasping element  674 , and multi-hook assembly  676 ), a magnet  688  (configured to attract and attach to magnet  678 ), a second half  690  of the hook-and-loop fastener (configured to attach to first half  680 ), and angled hooks  692  (configured to attach to hook  682  and loop  684 ). 
     Column  674  shows various types of fasteners that may be used to fasten objects to tissue, the fasteners including, for example, a T-tag  694 , a coil  696  with a sharpened tip, a ring element  698 , and a self-expanding hook assembly  699 . Any of the fasteners in column  674  may be used with any of the engagement elements in column  672 , to fasten the engagement elements in column  672  to tissue. The assembly of the fastener from column  674  and the engagement element from column  672  may be used in systems  100 ,  200 , and  300  as anchors  108 ,  110 ,  208 ,  210 ,  308 , and  310 , respectively. It also is contemplated that any of the fasteners in column  674  may be used in systems  100  and  200  to fasten anchors  112  and  212  to target areas  104  and  204 , respectively. The listing in table  668  shows exemplary aspects, and is not an exhaustive listing of all possibilities. For example, any of the engagement elements and/or fasteners of systems  100 ,  200 , and  300  may form part of table  668 . 
       FIGS. 7A-7C  show a system  700  for retracting tissue  702 . Tissue  702  may include, for example, an area  704  targeted for removal, such as an area with a lesion. System  700  may include an introducer  706  for providing access to tissue  702 . Introducer  706  may deploy anchors  708  and  712  to engage a portion of tissue  702  opposing or otherwise facing target area  704 , and target area  704  itself, respectively. 
       FIG. 7A  shows system  700  in a delivery configuration for facilitating navigation of the distal end of introducer  706  to target area  704 . Anchors  708  and  712  may be received within a holder  762 . A positioning instrument  718  also may be received within holder  762 . By moving positioning instrument  718  distally, the user may push anchors  708  and  712  distally to deploy anchors  708  and  712 .  FIG. 7B  shows holder  762  extending distally from introducer  706 , and anchor  712  being pushed distally out of holder  762 , during deployment. The distal end of holder  762  may move anchor  712  into an open configuration as anchor  712  exits from holder  762  (as seen in  FIG. 7B ). The open anchor  712  may receive target area  704 . As anchor  712  separates from holder  762 , anchor  712  may close on target area  704 , thereby grasping target area  704 . A tether  714  may be coupled on one end to anchor  712 , and on the other end to anchor  708 . 
     With anchor  712  grasping target area  704 , the user may deflect introducer  706  to move holder  762  and clip  708  toward a portion of tissue  702  that may face or otherwise oppose target area  704 . The user may use positioning instrument  718  to push anchor  708  out of holder  762  to cause anchor  708  to grasp tissue  702 . These movements may impart a tensile force on tether  714 , which may pull anchor  712 , and thereby retract target area  704 , as shown in  FIG. 7C . The retraction may be along a vector extending between target area  704  and anchor  712 . The movement also may stretch tether  714 . 
     A cutting instrument  720  may be used to cut retracted target area  704 . If the cutting affects target area  704  in a way that causes slack to develop in tether  714 , the position of anchor  708  may be adjusted by, for example, using positioning instrument  718  to free anchor  708  from tissue  702 , reposition anchor  708 , and then release anchor  708  such that anchor  708  may engage another portion of tissue  702 . This adjustment may provide a user with the ability to utilize different vectors of retraction (e.g., directions and/or magnitudes of retraction) with respect to target area  704 . This control over the vector of retraction may provide the user with an enhanced ability to expose and/or visualize the cutting plane the user uses to guide cutting, with cutting instrument  720 , for purposes of removing target area  704 . 
     Introducer  706  may, for example, be similar to introducer  106  of system  100 . Introducer  706  may include an instrument lumen  701 . Instrument lumen  701  is visible in the cutaway view of  FIG. 7A ; and also in  FIG. 7B , where a portion of introducer  706  has been made transparent to show internal features. It is contemplated that other lumens (not shown) may be provided for lighting, imaging, and/or moving material. 
     Holder  762  may be slidable within instrument lumen  701  of introducer  706 , such that the user may retract holder  762  into instrument lumen  701  during navigation of introducer  706  to target area  704 , and extend holder  762  out of the distal end of introducer  706  to facilitate deployment of anchors  708  and  710  onto tissue  702 . Holder  702762  may have a proximal portion  703  and a distal portion  705 . A lumen  760  may extend through proximal and distal portions  703  and  705 . Proximal portion  703  may be wider than distal portion  705 . Additionally or alternatively, an internal diameter of proximal portion  703  may be greater than an internal diameter of distal portion  705 . Thus, lumen  760  may be wider in proximal portion  703  than in distal portion  705 . The transition from proximal portion  703  to distal portion  705  may be gradual, such that holder  702762  and lumen  760  may taper at the transition. 
     Anchor  708  may include a fastener  738  that secures to tissue  702 , such as a grasping element formed by jaws  707  and  709 . Jaws  707  and  709  may be pivotably attached to each other at a fulcrum  711 . A biasing element  713 , such as a torsion spring member, may engage jaws  707  and  709 , to bias jaws  707  and  709  to a closed configuration. As jaws  707  and  709  move to the closed configuration, the distal tips of jaws  707  and  709  at a first end  732  of anchor  708  may move toward each other. If unobstructed, the distal tips of jaws  707  and  709  may move into contact with each other. At a second end  734  of anchor  708 , on the other side of fulcrum  711 , proximal tips of jaws  707  and  709  may move away from each other as jaws  707  and  709  move to the closed configuration. As jaws  707  and  709  move to the open configuration (e.g., against the biasing force exerted by biasing element  713 ), the proximal tips of jaws  707  and  709  at second end  734  may move toward each other, and the distal tips  707  and  709  at first end  732  may move away from each. Exerting a force on one or more of jaws  707  and  709 , at or near the proximal tips of jaws  707  and  709 , may move jaws  707  and  709  to the open configuration, allowing jaws  707  and  709  to receive tissue  702 . Removing that force may allow jaws  707  and  709  to move to the closed configuration to fasten to tissue  702 . Protuberances  715  and  717 , such as sloped protrusions, curved protrusions, ramps, or the like, may be provided at the proximal tips of jaws  707  and  709  to facilitate moving jaws  707  and  709  to the open configuration, as described below. Anchor  712  may be similar to anchor  708 . Anchors  708  and  712  may be connected by tether  714 . 
     Prior to deployment, anchors  708  and  712  may be serially arranged in lumen  760  at proximal portion  703  of holder  762 . First end  732  of anchor  708  may extend toward the distal end of holder  762 , and may engage the second end (e.g., the proximal end) of anchor  712 . Second end  734  of anchor  708  may engage the distal end of positioning instrument  718 . Lumen  760  at proximal portion  703  may be sized such that anchors  708  and  712  may be in their closed configurations. Alternatively, lumen  760  may be sized such that anchors  708  and  712  may be in a partially open configuration due, for example, to engagement between the inner surfaces of holder  762  and protuberances  715  and  717 . Tether  714  may be contained in lumen  760  alongside anchors  708  and  712 . Alternatively, one or more of anchors  708  and  712  may be flipped end-to-end in lumen  760 . 
     With introducer  706  at or near target area  704 , the user may move positioning instrument  718  distally to push anchors  708  and  712  through lumen  760  from proximal portion  703  of holder  762  to distal portion  705 . With continued distal movement, positioning instrument  718  may begin to push anchor  712  out of holder  762 . As the second end of anchor  712  reaches the transition between proximal portion  703  and distal portion  705  of holder  762 , the protuberances on anchor  712  may engage the interior surface(s) of holder  762  due to the reduction in width of holder  762  at distal portion  705 . This engagement may exert a compressive force on the proximal tips of the jaws of anchor  712 , thereby causing the distal tips of the jaws to move away from each other ( FIG. 7B ) to receive target area  704 . Continued distal movement of positioning instrument  718  may move anchor  712  entirely out of holder  762 . As the protuberances on anchor  712  disengage from holder  762 , the biasing element of anchor  712  may force the jaws of anchor  712  into the closed configuration, thereby fastening the jaws to target area  704 . By these steps, anchor  712  (and anchor  708 ) may automatically open and close during deployment due to its interactions with holder  762 . 
     The user may move introducer  706  to a position on tissue  702  opposing or otherwise facing target area  704 . Due to the connection between anchor  708  (still in holder  706 ) and anchor  712 , via tether  714 , this movement may retract target area  704 . With the desired vector of retraction achieved, the user may deploy anchor  708  onto tissue  702  in a manner similar to how anchor  712  was deployed onto target area  704 , to fix the vector of retraction (see  FIG. 7C ). The user then may remove holder  762  from instrument lumen  760 . 
     With target area  704  retracted, the user may cut target area  704  with cutting instrument  720  (which may be similar to any of the aforementioned cutting instruments in this disclosure). During cutting, target area  704  may form a flap that may be drawn toward anchor  708  by tension and/or biasing forces in tether  714 . This may lead to a reduction in the retraction force on target area  704 . In order to increase the retraction force, the user may withdraw cutting instrument  720 , and reintroduce positioning instrument  718 . The user may extend positioning instrument  718  out of introducer  706 . Positioning instrument  718  may include a grasping element  719 , such as forceps jaws. The user may exert a compressive force on the proximal tips of jaws  707  and  709 , to move anchor  708  to the open configuration, so that tissue  702  is released. Positioning instrument  718  and/or introducer  706  may move anchor  708  to another location on tissue  702  that may exert a different retracting force on target area  704 . The user may then return to cutting target area  704 . This process may be repeated until target area  704  is removed. 
     Other variations are contemplated. For example, a plurality of tethers  714  may be used. Each of the tethers  714  may be coupled at their first ends to the same anchor  712 . Each of the tethers  714  may have their own anchor  708  at their second end. Each of the tether-anchor pairings may be attached to a different location of tissue  702 , thus imparting multiple retraction forces with different vectors on target area  704 . 
     Alternatively, multiple anchor-tether-anchor assemblies (e.g., similar to the assembly of anchor  708 , tether  713 , and anchor  712 ) may be used to retract target area  704 . For example, one anchor-tether-anchor assembly may be used to initially retract target area  704  during a first cutting phase. Once slack develops in that anchor-tether-anchor assembly, and the desired amount and/or direction of retraction is not provided, another anchor-tether-anchor assembly may be deployed to increase the amount and/or change the direction of retraction. The anchor-tether-anchor assemblies may be identical, or may have one or more differences. For example, one may have a shorter tether, different tether construction, and/or a different type of anchor. 
     Alternatively, tether  714  may be omitted. Anchors  708  and  710  may be deployed separate from each other to engage tissue without necessarily being used for tissue retraction. For example, anchors  708  and  710  may be used as clips for closing apertures in tissue, positioning tissue, pinching blood vessels, or performing any other suitable task. 
       FIGS. 8 and 9  show anchors  808  and  908 . Either of anchors  808  and  908  may be used in place of anchors  708  and  712  of system  700 . Anchors  808  and  908  may include integral jaws  807  and  809 , and  907  and  909 , respectively, forming figure eights. 
     With respect to anchor  808 , a biasing element  813  may engage opposing surfaces of a proximal portion of anchor  808 . Biasing element  813  may include, for example, a compression spring. In  FIG. 8 , biasing element  813  is shown in a partially compressed state, indicative of how biasing element  813  would look when a compressive force is exerted on the proximal portion of anchor  808 . In the absence of the force, the distal tips of jaws  807  and  809  may move toward each other and/or into engagement. 
     With respect to anchor  908 , a biasing element  913  may engage opposing surfaces of a distal portion of anchor  908 . Biasing element  913  may include, for example, a tension spring. In  FIG. 9 , biasing element  913  is shown in a partially stretched state, indicative of how biasing element  913  would look when a compressive force is exerted on the proximal portion of anchor  908 . In the absence of the force, the distal tips of jaws  907  and  909  may move toward each other and/or into engagement. 
       FIG. 10  shows a distal end view of a holder  1062 . A lumen  1060  is show within holder  1062 . Holder  1062  may include interior surface regions at its distal end that have different internal diameters. For example, the interior surface of holder  1062  may include opposing regions  1023  and  1025 . Opposing regions  1023  and  1025  may be equally spaced from a central longitudinal axis of holder  1062 . The interior surface of holder  1062  also may include opposing regions  1027  and  1029 . Opposing regions  1027  and  1029  may gradually slope toward the central longitudinal axis of holder  1062 . The interior surface of holder  1062  also may include opposing regions  1031  and  1033 . Opposing regions  1031  and  1033  may provide a transition between opposing regions  1023  and  1025  and adjacent opposing regions  1027  and  1029 . Opposing regions  1031  and  1033  may be substantially coplanar, and/or may be straight sections of the interior surface of holder  1062 . The portion of the interior surface of holder  1062  having opposing regions  1023  and  1025 ,  1027  and  1029 ,  1031  and  1033  may be the distal portion of holder  1062  only. The interior surface of the proximal portion of holder  1062  may be circular, and/or may have an inner diameter similar to that defined between opposing regions  1023  and  1025 . 
     Holder  1062  may be used in place of holder  762  in system  700 . Any of anchors  708 ,  712 ,  808 , and  908  may be positioned in lumen  1060 . Regions of the interior surface of holder  1062  may engage the anchors. Using anchor  708  as an example, anchor  708  may be positioned in lumen  1060  in the proximal portion of holder  1062 . Anchor  708  may be in its closed configuration, or close to its closed configuration depending on the width of lumen  1060  in the proximal portion of holder  1062 . Positioning instrument  718  may move anchor  708  distally, causing the distal portions of jaws  707  and  709  to extend out of holder  1062 , and bringing the proximal portions of jaws  707  and  709  into engagement with opposing regions  1023  and  1025 . The user may rotate holder  1062  clockwise relative to anchor  708  to bring the proximal portions of jaws  707  and  709  into engagement with opposing regions  1027  and  1029 . Continued clockwise rotation of holder  1062  may compress the proximal portions of jaws  707  and  709 , due to the decreasing distance between diametrically opposite portions of opposing regions  1027  and  1029 . Where the proximal portions of jaws  707  and  709  approach opposing regions  1031  and  1033 , anchor  708  may achieve the open configuration. Open jaws  707  and  709  may receive tissue (not shown). Continued clockwise rotation of holder  1062  may cause the proximal portions of jaws  707  and  709  to separate from opposing regions  1027  and  1029 , and move radially outward alongside opposing regions  1031  and  1033 , due to the biasing force exerted on jaws  707  and  709  by biasing element  713 . Anchor  708  may move back towards its closed configuration, thereby fastening jaws  707  and  709  onto the tissue. Any of anchors  712 ,  808 , and  908  may be deployed from holder  1062  in a similar manner. 
       FIG. 11  shows a holder  1162  similar to holder  762 . For example, holder  1162  may include a proximal portion  1103 , a distal portion  1105 , and a lumen  1160 , wherein a width of lumen  1160  is greater in proximal portion  1103  than in distal portion  1105 . In the drawing, a portion of holder  1162  has been cut away to expose the interior of holder  1162  and anchors (e.g., anchors  1108 ,  1112 , and  1121 ) housed therein. Anchors  1108 ,  1110 , and  1121  may be similar to anchors  708  and  712 . For example, anchor  1108  may include jaws  1107  and  1109  that pivot about a fulcrum  1111 , and jaws  1107  and  1109  may be biased toward a closed configuration by a biasing element  1113  (e.g., a torsion spring). In the closed configuration, distal tips of jaws  1107  and  1109  may be in contact, or may exert a compressive force on tissue between jaws  1107  and  1109 . Exerting a compressive force on proximal tips of jaws  1107  and  1109  may move jaws  1107  and  1109  to an open configuration by overcoming the biasing force exerted by biasing element  1113 . Anchors  1112  and  1121  may be similar to anchor  1108 . 
     Prior to deployment from holder  1162 , anchors  1108 ,  1112 , and  1121  may be arranged end-to-end, with the distal tips of the jaws of anchor  1121  clamped onto the proximal tips of jaws  1107  and  1109  of anchor  1108 . Similarly, the distal tips of jaws  1107  and  1109  of anchor  1108  may be clamped onto the proximal tips of the jaws of anchor  1112 . 
     During deployment, a positioning instrument (not shown, but similar to positioning instrument  718 ) may be used to push anchors  1108 ,  1112 ,  1121  distally through lumen  1160 . Anchor  1112  may begin to exit from the distal end of holder  1162 . As the distal tips of jaws  1107  and  1109  of anchor  1108  reach the transition between proximal portion  1103  and distal portion  1105  of holder  1162 , the reduction in diameter of holder  1162  may cause the interior surfaces of holder  1162  to exert a compressive force on the distal tips of jaws  1107  and  1109  of anchor  1108 . This compressive force may act on the proximal tips of the jaws of anchor  1112 , thus moving anchor  1112  to its open configuration. Anchor  1112  may receive tissue between its jaws. 
     As the positioning instrument pushes anchors  1108 ,  1112 ,  1121  further distally, the proximal tips of the jaws of anchor  1108  may be compressed by holder  1162  (and the distal tips of the jaws of anchor  1121 ) at the transition between proximal portion  1103  and distal portion  1105  of holder  1162 . Anchor  1108  may release anchor  1112 , allowing anchor  1112  to move to its closed configuration to fasten to the tissue. Anchor  1108  may then be ready to receive tissue. This process may be repeated to deploy additional anchors. While three anchors are shown, it should be understood that any suitable number of anchors may be provided in holder  1162 . After being deployed, the positioning instrument may be used to exert a compressive force on the proximal tips of any of the jaws of anchors  1108 ,  1112 ,  1121 , to move the anchor(s) to the open configuration so that tissue is released. The positioning instrument  1118  and/or introducer  1106  may move any of anchors  1108 ,  1112 ,  1121  to other locations. 
     It is contemplated that anchors  1108 ,  1112 , and  1121  may be deployed without being tethered, to engage tissue without necessarily cooperating to retract tissue. For example, anchors  1108 ,  1112 , and  1121  may be used as clips for closing apertures in tissue, positioning tissue, pinching blood vessels, or performing any other suitable task. Alternatively, at least two of anchors  1108 ,  1112 , and  1121  may be linked by a tether (not shown, but similar to tethers  114 ,  214 , and  714 ) so that two or more of anchors  1108 ,  1112 ,  1121  may be used for tissue retraction. While system  1100  has been described above as having holder  1162  with narrowed distal portion  1105 , it is contemplated that holder  1062  of  FIG. 10  may replace holder  1162 . In such an example, relative rotation of holder  1062  relative to anchors  1108 ,  1112 , and  1121  may be used to effect opening and closing of anchors  1108 ,  1112 , and  1121 . 
       FIGS. 12A-12F  show a system  1200  for retracting tissue  1202 . Tissue  1202  may include, for example, an area  1204  targeted for removal, such as an area with a lesion. System  1200  may include an introducer  1206  for providing access to tissue  1202 . Introducer  1206  may facilitate the deployment of anchors  1208  and  1212  onto tissue  1202 , such as onto target area  1204  and a portion of tissue  1202  opposing or otherwise facing target area  1204 . A tether  1214  that may couple anchors  1208  and  1212  may also be deployed to aid in retracting target area  1204 . 
       FIG. 12A  shows introducer  1206  in a delivery configuration for facilitating navigation of the distal end of introducer  1206  to target area  1204 . Anchors  1208  and  1212  may be received within a holder  1262 . A positioning instrument  1218  also may be received within holder  1262 . Positioning instrument  1218  may be releasably coupled to anchor  1212 . By moving positioning instrument  1218  distally, the user may push anchors  1208  and  1212 , and tether  1214  distally to eject anchors  1208  and  1212 , and tether  1214  out of holder  1262  (see  FIG. 12B ). Anchor  1208  may be ejected in a closed configuration. Anchor  1212  may initially be ejected in a closed configuration, but once ejected, positioning instrument  1218  may be actuated to move anchor  1212  to an open configuration for receiving target area  1204 . Positioning instrument  1218  may be actuated again to move anchor  1212  to a closed configuration to fasten anchor  1212  to target area  1204 , as seen in  FIG. 12C . 
     With anchor  1212  fastened to target area  1204 , the user may release positioning instrument  1218  from anchor  1212 . The user may maneuver introducer  1206  toward anchor  1208 , and may releasably couple introducer  1206  to anchor  1208  (see  FIGS. 12D  and  12 E). Using introducer  1206  and positioning instrument  1218 , the user may move anchor  1208  to a portion of tissue  1202  opposing or otherwise facing target area  1204 . This movement may impart a tensile force on tether  1214 , which may pull anchor  1212 , and thereby retract target area  1204  ( FIG. 12E ). When a desired vector of retraction is achieved, the user may actuate positioning instrument  1218  to open anchor  1208 . This may allow anchor  1208  to receive tissue  1202 , after which positioning instrument  1218  may close anchor  1208  to fasten anchor  1208  to tissue  1202 . 
     A cutting instrument  1220  (similar to any of the aforementioned cutting instruments in this disclosure) may be used to cut retracted target area  1204  (see  FIG. 12F ). If the cutting reduces the tension in tether  1214 , such that the retraction of target area  1204  is no longer adequate, the position of anchor  1208  may be readjusted. Readjustment may be accomplished by releasably coupling positioning instrument  1218  to anchor  1208  (see  FIG. 12D ), actuating positioning instrument  1218  to open anchor  1208  to release tissue  1202 , moving anchor  1208  to another position on tissue  1202  at which a new desired vector of retraction is achieved, and actuating positioning instrument  1218  to close anchor  1208  to fasten anchor  1208  to tissue  1202  at the new position. This readjustment may provide a user with the ability to utilize different vectors of retraction (e.g., directions and/or magnitudes of retraction) with respect to target area  1204 . This control over the vector of retraction may provide the user with an enhanced ability to expose and/or visualize the cutting plane the user uses to guide cutting, with cutting instrument  1220 , for purposes of removing target area  1204 . Additionally or alternatively, positioning instrument  1218  may be used to move anchor  1212  from target area  1204  to another target area for retraction and removal of the new target area. 
     Introducer  1206  may be similar to any of the aforementioned introducers described in this disclosure. Introducer  1206  may include lumens, one of which may be an instrument lumen  1260 . Holder  1262  may include a sleeve that may be slidable within instrument lumen  1260  such that the distal end of holder  1262  may be extendable out of introducer  1206  (e.g., during deployment of anchors  1208  and  1212 ) and retractable into introducer  1206  (e.g., during insertion and maneuvering of the distal portion of introducer  1206  to target area  1204 ). 
     Anchor  1208  may include a base  1244 . Base  1244  may include a sleeve or capsule having an internal lumen. Anchor  1208  also may include a fastener  1238  that secures to tissue  1202 , such as a grasping element formed by jaws  1207  and  1209 . Fastener  1238  may extend distally out from the distal end of base  1244 . Jaws  1207  and  1209  may have a closed configuration (seen in  FIG. 12A ) and an open configuration (similar to the open configuration of anchor  1212  in  FIG. 12B ). 
     Anchor  1208  also may include an actuation element  1235 . Actuation element  1235  may include a loop  1237  and a shaft  1239 . Loop  1237  may extend proximally out from the proximal end of base  1244 . Loop  1237  may be coupled to fastener  1238  by shaft  1239 . Shaft  1239  may extend through base  1244 . Jaws  1207  and  1209  may occupy the closed configuration when movement of loop  1237  and shaft  1239  in the proximal direction draws jaws  1207  and  1209  toward base  1244 . The distal end of base  1244  may exert a constraining force on jaws  1207  and  1209 , thus holding them in the closed configuration. Movement of loop  1237  and shaft  1239  in the distal direction may extend jaws  1207  and  1209  distally away from base  1244 , removing the constraining force on jaws  1207  and  1209 , and thereby allowing jaws  1207  and  1209  to move to the open configuration. Anchor  1212  may be similar to anchor  1208 . Anchors  1208  and  1212  may be connected by tether  1214 , which may be similar to tethers  114 ,  214 ,  714 . Ends of tether  1214  may be attached to the bases of anchors  1208  and  1212 . Alternatively, tether  1214  may be omitted. In such an example, anchors  1208  and  1212  may be used as individual redeployable surgical clips. 
     Positioning instrument  1218  may include a receiver  1241  and a manipulation element  1243 . Receiver  1241  may include a sleeve or capsule having a lumen (not shown). Manipulation element  1243  may be movable in proximal and distal directions within the lumen of receiver  1241 , such that manipulation element  1243  may be extendable out of the distal end of receiver  1241 , and retractable into the distal end or receiver  1241 .  FIG. 12D  shows manipulation element  1243  extended distally out of the distal end of receiver  1241 . Manipulation element  1243  may be configured to releasably engage loop  1237  of actuation element  1235  of anchor  1208 . For example, manipulation element  1243  may include a bent distal end  1245 . 
     Once bent distal end  1245  engages loop  1237 , manipulation element  1243  may be withdrawn into receiver  1241  to proximally pull anchor  1208  to receiver  1241 . Initially, loop  1237  and a proximal portion of shaft  1239  may be drawn into receiver  1241 . Further withdrawal of manipulation element  1243  may draw base  1244  to receiver  1241 , such that receiver  1241  may receive base  1244 . The distal portion of receiver  1241  and the proximal portion of base  1244  may include cooperating coupling elements  1247  and  1249  for releasably coupling receiver  1241  and base  1244 , allowing receiver  1241  to temporarily acquire base  1244 . When coupling elements  1247  and  1249  are engaged, receiver  1241  and base  1244  may be fixed relative to each other. Coupling elements  1247  and  1249  may include any suitable releasable mechanical coupling, such as a snap-fit coupling, a latching arrangement, a magnetic coupling, or the like. 
     With coupling elements  1247  and  1249  engaged, manipulation element  1243  may extend distally to move loop  1237 , shaft  1239 , and jaws  1207  and  1209  distally relative to base  1244 . This may move jaws  1207  and  1209  to their open configuration, such that anchor  1208  may acquire tissue  1202 , and/or release previously acquired tissue  1202 . Movement of manipulation element  1243  proximally may move jaws  1207  and  1209  back to their closed configuration to fasten anchor  1208  to newly acquired tissue. After anchor  1208  is fastened to tissue  1202 , coupling elements  1247  and  1249  may be released from each other, and manipulation element  1243  may be released from loop  1237 . Positioning instrument  1218  may be moved away from anchor  1208 , leaving anchor  1208  in place on the tissue. This process may be repeated whenever deployment and/or redeployment of anchors  1208  and  1212  onto tissue is desired. 
       FIG. 13  shows portions of another positioning element  1318  and another anchor  1308 , similar in ways to positioning element  1218  and anchor  1208  of system  1200 . It is contemplated that the portions of positioning element  1318  and anchor  1308  may be used in place of similar portions of positioning element  1218  and anchor  1208 . Positioning element  1318  may include a receiver  1341  and a manipulation element  1343  with a bent distal end  1245 . Anchor  1308  may include a fastener  1338  with jaws  1307 ,  1309 ; an actuation element  1335  including a shaft (not shown) and a loop  1337 ; and a base  1344 . 
     Receiver  1341  and base  1344  may include cooperating coupling elements  1347 ,  1349 . Coupling element  1347  may include a groove or channel extending proximally from the distal end of receiver  1341 , and laterally, forming an L-shaped cavity. Coupling element  1349  may include a protrusion protruding from an external surface of base  1344 . In use, manipulation element  1343  may engage loop  1337 , and may draw base  1344  into receiver  1341 . Coupling element  1349  may be aligned with coupling element  1347 , such that coupling element  1349  may move proximally through coupling element  1347  as manipulation element  1343  moves proximally. By twisting manipulation element  1343 , anchor  1308  may be rotated about its central longitudinal axis, causing coupling element  1349  to travel laterally through coupling element  1347 . This releasably couples positioning element  1318  to anchor  1308 . 
     With positioning element  1318  releasably coupled to anchor  1308 , receiver  1341  and base  1344  may be fixed relative to each other. Manipulation element  1343  may be pulled proximally to close jaws  1307 ,  1309 , for fastening anchor  1308  to tissue. Manipulation element  1343  may be pushed distally to open jaws  1307 ,  1309 , to allow jaws  1307 ,  1309  to acquire tissue, and/or to release jaws  1307 ,  1309  from previously acquired tissue for redeployment of anchor  1308 . 
       FIG. 14  shows portions of another positioning element  1418  and another anchor  1408 , similar in ways to positioning elements  1218  and  1318  and anchors  1208  and  1308  of systems  1200  and  1300 , respectively. It is contemplated that the portions of positioning element  1418  and anchor  1408  may be used in place of similar portions of the other positioning elements and anchors. Positioning element  1418  may include a receiver  1441  and a manipulation element  1443  with a bent distal end  1445 . Anchor  1408  may include a fastener  1438  with jaws  1407  and  1409 ; an actuation element  1435  including a shaft  1439  and a loop  1437 ; and a base  1444 . 
     Receiver  1441  and base  1444  may include cooperating coupling elements  1447  and  1449 . Coupling elements  1447  and  1449  may include, for example, mating geometric structures, such as mating screw threads. Coupling element  1447  may include screw threads on an interior surface of receiver  1441 . Coupling element  1449  may include screw threads on an exterior surface of base  1444 . In use, manipulation element  1443  may engage loop  1437 , and may draw the proximal end of base  1444  to the distal end of receiver  1441 . By twisting manipulation element  1443 , possibly assisted by proximal pulling of manipulation element  1443 , anchor  1408  may be rotated about its central longitudinal axis, thereby facilitating engagement of coupling elements  1447  and  1447 . Further twisting of manipulation element  1443  may screw anchor  1408  into positioning element  1418 . This releasably couples positioning element  1418  to anchor  1408 . 
     With positioning element  1418  releasably coupled to anchor  1408 , receiver  1441  and base  1444  may be fixed relative to each other. Manipulation element  1443  may be pulled proximally to close jaws  1407  and  1409 , for fastening anchor  1408  to tissue. Manipulation element  1443  may be pushed distally to open jaws  1407  and  1409 , to allow jaws  1407  and  1409  to acquire tissue, and/or to release jaws  1407  and  1409  from previously acquired tissue for redeployment of anchor  1408 . 
       FIG. 15  shows a portion of a manipulation element  1543 , and in particular, a bent distal end  1545  of manipulation element  1543 . Manipulation element  1543  may be similar in ways to manipulation elements  1243 ,  1343  and  1443 . Bent distal end  1545  may engage a loop  1537  of an actuation element  1535 . Loop  1537  may be similar in ways to loops  1237 ,  1337  and  1437 . Loop  1537 , however, may have a discontinuity  1551  formed therein. When enough force is applied by bent distal end  1545  at discontinuity  1551 , bent distal end  1545  may spread loop  1537  apart, allowing bent distal end  1545  to enter or exit from loop  1537  via discontinuity  1551 . Loop  1537  may be used in place of any of loops  1237 ,  1337 , and  1437  to facilitate entry of manipulation elements into the loops, and withdrawal of manipulation elements out of the loops. 
       FIGS. 16A and 16B  show portions of another positioning element  1618  and another anchor  1608 . It is contemplated that portions of positioning element  1618  and anchor  1608  may be used in place of similar portions of any of the other positioning elements described in this disclosure, such as positioning elements  1218 ,  1318 , and  1418 . Positioning element  1618  may include a receiver  1641  and a manipulation element  1643  with an enlarged distal end  1645 . Enlarged distal end  1645  may include a spherical ball, a circular plate, and/or any other suitable protuberance. Anchor  1608  may include a fastener with jaws (not shown); an actuation element  1635  including a shaft  1639  and a socket  1637 ; and a base  1644 . The fastener may include, for example, aspects of fasteners  1238 ,  1338 ,  1438 . 
     Receiver  1641  and base  1644  may include cooperating coupling elements  1647 ,  1649 . Coupling elements  1647 ,  1649  may include, for example, mating snap-fit elements. Coupling element  1647  may include one or more protrusions an the distal end of the interior surface of receiver  1641 . Coupling element  1649  may include one or more indentations or notches on an exterior surface of a proximal end of base  1644 , or one or more apertures through one or more sides of the proximal end of base  1644 . 
       FIG. 16A  shows coupling elements  1647  and  1649  releasably coupled to each other to fix receiver  1641  relative to base  1644 . Enlarged distal end  1645  of manipulation element  1643  also may be releasably coupled to socket  1637  of actuation element  1635 . Moving the releasably coupled manipulation element  1643  and actuation element  1635  distally may open the fastener, while moving them proximally may close the fastener. In  FIG. 16A , the fastener is closed. Further proximal movement of socket  1637  may be prevented by engagement of the proximal end of socket  1637  with a reduced diameter portion  1653  of base  1644 . The closed fastener may be fastened to tissue. To leave anchor  1608  in place on the tissue, manipulation element  1643  may be pulled proximally to pull enlarged distal end  1645  out of socket  1637 , as shown in  FIG. 16B . Continued proximal pulling of manipulation element  1643  may bring enlarged distal end  1645  into contact with a reduced-diameter portion  1657  of receiver  1641 . As enlarged distal end  1645  moves proximally through reduced-diameter portion  1657 , enlarged distal end  1645  may force open reduced-diameter portion  1657 , which may release coupling element  1647  from coupling element  1649 , thereby allowing positioning element  1618  to release from anchor  1608 . 
     In order to remove anchor  1608  from tissue for redeployment, the distal end of receiver  1641  may move toward the proximal end of base  1644 . Sloped surfaces of coupling element  1647  may engage the proximal end of base  1644 , which may cause coupling elements  1647  to move outwardly and onto the exterior surface of base  1644 . Receiver  1641  may move distally relative to base  1644  until coupling element  1647  snaps into engagement with coupling element  1649 . Manipulation element  1643  may move to bring enlarged distal end  1645  into engagement with reduced-diameter portion  1657 , to help force reduced-diameter portion  1657  outward, thereby facilitating coupling of receiver  1641  to base  1644 . Manipulation element  1643  may move distally into engagement with socket  1637  to push socket  1637  distally, thereby opening the fastener. Enlarged distal end  1645  may snap into socket  1637  when pushing socket  1637  distally. In one example, a protrusion, shoulder, or other abutment (not shown) may be provided on the interior surface of base  1644  to engage the distal end of socket  1637 , for limiting further distal travel of socket  1637  beyond the point at which the fastener is fully opened. When socket  1637  contacts the protrusion, shoulder, or abutment, forcibly pushing enlarged distal end  1645  against the proximal end of socket  1637  may cause enlarged distal end  1645  to snap into socket  1637 . 
     With the fastener open, anchor  1608  may be released from the one location on the tissue and brought to another location on the tissue. The fastener may be closed onto the tissue at the new location by moving manipulation element  1643  proximally, thereby moving actuation element  1635  proximally, due to receipt of enlarged distal end  1645  into socket  1637 . Positioning element  1618  may then be released from anchor per the steps described above. This process may be repeated whenever redeployment is desired. 
       FIG. 17  shows a perspective view of a portion of an actuation element  1735  which may be similar to actuation element  1635 . Actuation element  1735  may be used in place of actuation element  1635 . Actuation element  1735  may include a socket  1737  at its proximal end. The proximal portion of actuation element  1735 , however, may extend proximally beyond the proximal end of base  1644 , and the rest of actuation element  1735  may be received in base  1644 . Lateral protrusions  1757  at the proximal end of socket  1737  may be configured to abut the proximal end of base  1644  when the fastener of anchor  1608  is fully opened. The abutting of lateral protrusion  1757  against the proximal end of base  1644  may hold socket  1737  in place to facilitate insertion of enlarged distal end  1645  of manipulation element  1643  into socket  1737  for use in closing the fastener. Socket  1737  may define a U-shaped recess to facilitate side entry of enlarged distal end  1645  into socket  1737 . It also is contemplated that the base of the U-shaped recess may be enlarged to further facilitate side entry of enlarged distal end  1645 . 
       FIG. 18  shows portions of another positioning element  1818  and another anchor  1808 , similar in ways to positioning element  1618  and anchor  1608 . Anchor  1808  may include a spring-biased fastener  1838  with jaws  1807  and  1809 . Fastener  1838  may be spring-biased by a biasing element  1859 , which may include a compression spring. A proximal end of biasing element  1859  may engage a base element  1861  at the proximal ends of jaws  1807  and  1809 . A distal end of biasing element  1859  may engage a stop  1863  that may be fixed relative to the distal end of a base  1844  of anchor  1808 . In the absence of a deforming force acting on biasing element  1859 , biasing element  1859  may move base element  1861  away from stop  1863 . This may draw jaws  1807  and  1809  toward the distal end of base  1844 , and causing jaws  1807  and  1809  to close due to engagement between jaws  1807  and  1809  and the interior surface of the distal end of base  1844  and/or engagement between jaws  1807  and  1809  and the exterior surface of stop  1863 . 
     Positioning element  1818  may be provided with a manipulation element  1843  having an enlarged distal portion  1845  that may be similar to enlarged distal end  1645 . Enlarged distal portion  1845  may include a circular plate, a spherical ball, and/or any other suitable form of enlargement. Enlarged distal portion  1845  may be used to engage a receiver (not shown) of positioning element  1818 , which may be similar to receiver  1641 , to facilitate engagement of a coupling element on the receiver with a coupling element (not shown) on base  1844 . The coupling elements may, for example, be similar to coupling elements  1647  and  1649 . Enlarged distal portion  1845  also may facilitate disengagement of the coupling elements. 
     When the coupling elements are engaged, manipulation element  1843  may be pushed distally through base  1844 . An extension  1865  extending distally from enlarged distal portion  1845  may engage base element  1861 . Extension  1865  may exert a distally-directed force on base element  1861 , causing compression of biasing element  1859 , and also causing jaws  1807  and  1809  to move to the opened position. Upon removal or reduction of the distally-directed force on base element  1861 , biasing element  1859  may move jaws  1807  and  1809  back to the closed position. 
       FIGS. 19A-19H  show a system  1900  for retracting tissue  1902 . Tissue  1902  may include, for example, an area  1904  targeted for removal, such as an area with a lesion. System  1900  may include an introducer  1906  for providing access to tissue  1902 . Introducer  1906  may facilitate the deployment of a tether  1914  through target area  1904 , and an anchor  1908  onto a portion of tissue  1902  opposing or otherwise facing target area  1904 . 
       FIG. 19A  shows introducer  1906  positioned near target area  1904 , and anchor  1908  extended distally from the distal end of introducer  1906 .  FIG. 19B  shows anchor  1908  in an open configuration, with its jaws  1907  and  1909  spread, for receiving target area  1904 . Tether  1914  may be secured to jaw  1907 .  FIG. 19C  shows anchor  1908  being moved to a closed configuration to penetrate target area  1904  with jaws  1907  and  1909 , and pass tether  1914  through target area  1904 . Tether  1914  may be grasped by jaw  1909 .  FIG. 19D  shows anchor  1908  moved back to the open configuration, with tether  1914  now threaded through target area  1904 . Anchor  1908  may be opened and closed through actuation of a positioning instrument (not shown). 
     The user may maneuver introducer  1906  and anchor  1908  to a portion of tissue  1902  opposing or otherwise facing target area  1904 . This movement may impart a tensile force on tether  1914 , which may pull tether  1914 , and thereby retract target area  1904  (seen in  FIG. 19E ). When a desired vector of retraction is achieved, the user may close anchor  1908  to fasten anchor  1908  to tissue  1202  at a desired location (seen in  FIG. 19F ). 
     A cutting instrument  1920  (similar to any of the aforementioned cutting instruments described in this disclosure) may be used to cut retracted target area  1904  (see  FIG. 19G ). If the cutting reduces the tension in tether  1914 , such that the retraction of target area  1904  is inadequate, the length of tether  1914  may be adjusted to increase the retraction. Readjustment may be accomplished by grasping a free end of tether  1914  with a forceps or other grasping instrument, and pulling the free end to tighten the portion of tether  1914  coupling anchor  1908  to target area  1904 , as shown in  FIG. 19H . 
     Introducer  1906  may be similar to any of the other introducers described in this disclosure. Introducer  1906  may include lumens, one of which may be an instrument lumen (not shown). An end cap  1926  may be provided at the distal end of introducer  1906 . End cap  1926  may include ports, one of which may be a port  1930 . Port  1930  may open into the instrument lumen. Anchor  1908  may be slidable within the instrument lumen, such that anchor  1908  may be housed within the instrument lumen during delivery, and may be extended out of the instrument lumen via passage through port  1930  to extend distally from the distal end of introducer  1906  for deployment. Movement of anchor  1908  into and out of introducer  1906  may be caused by a positioning instrument (not shown) releasably coupled to anchor  1908 . The positioning instrument may, for example, be similar to any of the aforementioned positioning instruments described in this disclosure. 
     Anchor  1908  may include jaws  1907  and  1909  and a base  1944 . Jaws  1907  and  1909  may be movable between open and closed configurations by moving relative to base  1944 . For example, jaws  1907  and  1909  may move toward the open configuration when moved distally relative to the distal end of base  1944 . Jaws  1907  and  1909  may move toward the closed configuration when moved proximally relative to the distal end of base  1944 . The arrangement and operation of jaws  1907  and  1909  and base  1944  may be similar to the arrangement and operation of similar components of anchors  1208 ,  1210 ,  1308 ,  1408 ,  1608 , and  1808 . The positioning instrument for operating jaws  1907  and  1909  may be similar to positioning instruments  1218 ,  1318 ,  1418 ,  1618 , and  1818 . 
     Tether  1914 , which may include a suture, chain, or other suitable structure and/or material, may extend along a portion of jaw  1907  such that a grabbing element  1967  extending laterally inward from jaw  1909  may hook a portion of tether  1914  as anchor  1908  is closed. In use, anchor  1908  may be positioned in the open configuration with jaws  1907  and  1909  over opposite sides of target area  1904  (as seen in  FIG. 19B ). Anchor  1908  may then be closed so that grabbing element  1967  pierces target area  1904  as jaw  1909  moves toward jaw  1907  (as seen in  FIG. 19C ). A hook feature  1969  at an end of grabbing element  1967  may interface with jaw  1907  to hook a loop  1971  of tether  1914  extending along first jaw  1907 . Anchor  1908  may once again be opened so that grabbing element  1967 , with tether  1914  hooked thereto, may be passed through target area  1904 , thereby anchoring tether  1914  to target area  1904 . 
     Jaw  1907  may include a notch  1973  along the interior surface of jaw  1907  at the distal end. Jaw  1907  also may include a slot  1975  extending laterally through the distal end thereof in communication with the notch  1973 . When loop  1971  of tether  1914  is hooked on notch  1973 , a portion of loop  1971  may extend across slot  1975 . Grabbing element  1967  may pass through slot  1975 , between opposing sides of notch  1973 , to hook loop  1971 . Jaw  1907  also may include an opening  1977  extending laterally therethrough, with opening  1977  separated from slot  1975  by a distance. Alternatively, jaw  1907  may include a loop, magnet, hook-and-loop fastener, screw, or latch, for mating with a catch, magnet, hook-and-loop fastener, threaded hole, or keeper on tether  1914 , to secure tether  1914  to jaw  1907 . 
     A length of tether  1914  may extend through base  1944  of anchor  1908 , with a proximal free end of tether  1914  protruding out from the proximal end of base  1944 . At its distal end, tether  1914  may be fed through opening  1977  so that a remaining distal length of tether  1914  may extend along the interior surface of jaw  1907 . Loop  1971  of tether  1914  may be hooked by opposing sides of notch  1973  so that a portion of loop  1971  extends across slot  1975 . Thus, when grabbing element  1967  is passed through slot  1975 , grabbing element  1967  may pass through loop  1971  to grab or hook a portion thereof 
     Grabbing element  1967  may extend laterally from the interior surface of jaw  1909 . Grabbing element  1967  may include hook feature  1969 , which may be defined by a J or L-shaped slot. The free end of grabbing element  1967  may have an angled surface  1979  configured so that, as grabbing element  1967  is inserted through slot  1975 , loop  1971  may be guided along angled surface  1979  until loop  1971  reaches hook feature  1969  and is received therein. When anchor  1908  is closed, at least a portion of grabbing element  1967  may be received within slot  1975  so that hook feature  1967  hooks loop  1971 . 
     The proximal free end of tether  1914  may extend out of the proximal end of base  1944  (as seen in  FIG. 19G ) when anchor  1908  is deployed. By pulling the free end, the portion of tether  1914  between target area  1904  and anchor  1908  may be tightened. A one-way mechanism (not shown) may be provided in base  1944 . The one-way mechanism may allow tightening of tether  1914 , while preventing loosening of tether  1914 . The one-way mechanism may include, for example, a ratchet assembly. Tether  1914  may be similar to other tethers described above. Additionally or alternatively, tether  1914  may include grooves and/or protrusions similar to a zip-tie or chain to facilitate one-way movement for tightening. Alternatively, tether  1914  may be omitted, and anchor  1908  may be used individually as a surgical clip. 
       FIGS. 20A and 20B  show a version of system  1900  in which tether  1914  may extend proximally from anchor  1908 , into port  1930 , through the instrument lumen, and out the proximal end of introducer  1906 . The user may adjust retraction on target area  1904  from the proximal end of introducer  1906  by pulling tether  1914 . The step of grasping tether  1914  using a forceps or the like may be avoided. 
     Another difference with  FIGS. 20A and 20B  is that tether  1914  may not extend through base  1944 . As such, the one-way mechanism need not be provided in base  1944 . Rather, the one-way mechanism may be provided in port  1930 , the instrument lumen, or at the proximal end of introducer  1906 , to prevent loosening of tether  1914  between target area  1904  and anchor  1908 . As explained above, the one-way mechanism may include a ratchet assembly, zip tie features, or the like. Additionally or alternatively, the one-way mechanism may include a tie down at the proximal end of introducer  1906  to prevent unwanted distal migration of tether  1914 . 
     In  FIG. 20A , cutting instrument  1920  may cut target area  1904  in a manner that produces a flap. This may cause slack to develop in the portion of tether  1914  between anchor  1908  and target area  1904 .  FIG. 20B  shows the portion of tether  1914  between anchor  1908  and target area  1904  after being tightened by pulling the proximal end of tether  1914  from the proximal end of introducer  1906 . 
       FIGS. 21A and 21B  show a version of system  1900  wherein the retraction vector acting on target area  1904  may be adjusted by deploying an auxiliary anchor  1910 . Auxiliary anchor  1910  may be maneuvered by introducer  1906  (or another introducer) into engagement with the portion of tether  1914  between anchor  1908  and target area  1904 . Auxiliary anchor  1910 , while holding tether  1914 , may be fastened to tissue  1902  at another location, thereby adjusting the magnitude and/or direction of the retraction force exerted on target area  1904  by tether  1914  and anchor  1908 . Additional auxiliary anchors may be deployed to further adjust the retraction vector. It is also contemplated that auxiliary anchor  1910  may be used to adjust the retraction vector of any of the other aforementioned tethers described in this disclosure. 
       FIG. 22  shows yet another exemplary version of an auxiliary anchor  2210  that may be used to adjust the retraction vector by engaging tether  1914  and tissue  1902 . Auxiliary anchor  2210  may include opposed jaws  2283  and  2285 . Jaws  2283  and  2285  may include biasing elements  2287 ,  2289 , such as torsion springs, to bias jaws  2283  and  2285  into closed configurations. Jaws  2283  and  2285  may be linked by a spring member  2291 . Spring member  2291  may include a tension spring that can be stretched to exert a retraction force between jaws  2283  and  2285 , and material grasped by jaws  2283  and  2285 . Opposite ends of spring member  2291  may be pivotably coupled to jaws  2283  and  2285  by swiveling links  2293 ,  2295 . In one example, jaw  2283  may be opened to receive tether  1914 , and closed to grasp tether  1914 . Jaws  2285  may be fastened to tissue after a desired amount of retraction force is exerted on tether  1914  via jaws  2283  and spring member  2291 . 
       FIGS. 23A and 23B  show a version of system  1900  wherein the retraction vector acting on target area  1904  may be adjusted by adjusting an angle of a swivel link  2393  pivotably coupled to base  1944  of anchor  1908  by a hinge  2395 . In  FIG. 23A , swivel link  2393  may be positioned relative to base  1944  such that their central longitudinal axes are coaxial. Swivel link  2392  may be pivoted relative to base  1944  such that their central axes are angled, as shown in  FIG. 23B . A locking mechanism, such as a ratchet assembly or the like, may be provided at hinge  2395  to maintain the angled orientation of swivel link  2392  relative to base  1944 . The angling of swivel link  2392  may redirect the direction of retraction force exerted on target area  1904 , and may increase the magnitude of the retraction force, to facilitate cutting of target area  1904 . It is contemplated that this swivel link connection may be provided between any of the aforementioned tethers and anchors in this disclosure. 
       FIGS. 24A and 24B  show a version of system  1900  wherein the retraction vector acting on target area  1904  may be adjusted by adjusting a distance between legs of tether  1914  in the portion of tether  1914  that extends between target area  1904  and anchor  1908 . The adjustment may be provided using an annular element  2397 . The user may slide annular element  2397  down tether  1914  from the position shown in  FIG. 24A , toward target area  1904 . Continued sliding of annular element  2397  toward target area  1904  to the position shown in  FIG. 24B  may reduce the length of tether  1914  passing through target area  1904  such that tether  1914  may cinch target area  1904 . The cinching may cause target area  1904  to tent upward. It is contemplated that annular element  2397  may be used with any version of system  1900  described in this disclosure. 
       FIGS. 25A and 25B  show a version of system  1900  wherein the retraction force exerted on target area  1904  by tether  1914  may be adjusted by heating tether  1914  and/or directing electrical energy into tether  1914 . In such an example, tether  1914  may be made using “muscle wire,” which may include, for example, a nitinol wire configured to contract when heat or electrical energy is applied. Base  1944  of anchor  1908  may include a port 2599 configured to receive, for example, the distal tip of cutting instrument  1920 . Cutting instrument  1920  may supply the energy for contracting tether  1914  via port 2599.  FIG. 25A  shows tether  1914 , and the retraction force exerted on target area  1904 , prior to contraction of tether  1914 .  FIG. 25B  shows tether  1914 , and the increased retraction force, after contraction of tether  1914 . It is contemplated that any of the aforementioned bases and tether arrangements in this disclosure may include muscle wire, and a port for directing energy into the muscle wire, to provide increased retraction through contraction of the muscle wire. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed devices and methods without departing from the scope of the disclosure. Other aspects of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the features disclosed herein. It is intended that the specification and examples be considered as exemplary only.