1. Any enveloping structure, such as the membranous covering of a muscle, nerve, or blood vessel. Any sheathlike structure. SYN: vagina (1). 2. The prepuce of male animals, especially of the horse. 3. A specially designed tubular instrument through which special obturators or cutting instruments can be passed, or through which blood clots, tissue fragments, calculi, etc. can be evacuated. 4. A tube used as an orthodontic appliance, usually on molars. [A.S. scaeth]
- anterior tarsal tendinous sheaths [TA] synovial tendon sheaths that allow movement of tendons across the anterior aspect of the tarsal bones, deep to the extensor retinacula; included are the tendinous sheaths (vagina tendini musculi...) of: (1) the tibialis anterior (muscle) [TA] (...tibialis anterioris [TA]), (2) the extensor hallucis longus (muscle) [TA] (...extensoris hallucis longi [TA]), and (3) the extensor digitorum longus (muscle) [TA] (...extensoris digitorum longi [TA]). SYN: vaginae tendinum tarsales anteriores [TA].
- axillary s. fibrous neurovascular s., formed as an extension of the prevertebral layer of deep cervical fascia through the cervicoaxillary canal, which enclosed the first part of the axillary artery, the axillary vein, and the brachial plexus.
- carotid s. [TA] the dense fibrous investment of the carotid artery, internal jugular vein, and vagus nerve on each side of the neck, deep to the sternocleidomastoid muscle; the layers of cervical fascia blend with it. SYN: vagina carotica [TA].
- carpal tendinous sheaths [TA] tendon sheaths occurring in relation to the wrist, allowing tendons to slide freely across the bones and bony formations of the wrist as they are held in place by the flexor and extensor retinacula. SYN: vaginae tendinum carpalium [TA].
- caudal s. a group of microtubules arranged cylindrically around the caudal pole of the nucleus in a developing spermatozoon.
- common flexor s. (of hand) [TA] the synovial palmar carpal tendinous s. that surrounds the eight tendons of the superficial and deep flexors of the digits of the hand as they pass through the carpal canal; it is commonly continuous with the synovial digital s. of the little finger. SYN: vagina communis tendinum musculorum flexorum (manus) [TA], ulnar bursa.
- common peroneal tendon s. the s. that surrounds the tendons of the fibularis (peroneus) longus and brevis muscles in their passage across the ankle. SYN: vagina communis tendinum musculorum fibularium communis [TA], vagina tendinum musculorum fibularium communis, vagina tendinum musculorum peroneorum communis.
- dentinal s. a layer of tissue relatively resistant to the action of acids, which forms the walls of the dentinal tubules. SYN: Neumann s..
- dorsal carpal tendinous sheaths [TA] synovial tendon sheaths enabling tendon movement across the posterior aspect of the wrist deep to the extensor retinaculum; they are the following six tendinous sheaths (vaginae tendinum... [TA]): (1) of abductor longus and extensor pollicis brevis (muscles) [TA] (...musculorum abductoris longi et extensoris pollicis brevis [TA]); (2) of extensors carpi radiales (muscles) [TA] (...musculi extensorum carpi radialium [TA]); (3) of extensor pollicis longus (muscle) [TA] (...musculi extensoris pollicis longi [TA]); (4) of extensor digitorum and extensor indicis (muscles) [TA] (...musculorum extensoris digitorum et extensoris indicis [TA]); (5) of extensor digiti minimi (muscle) (...musculi extensoris digiti minimi [TA]); and (6) of extensor carpi ulnaris (muscle) [TA] (...musculi extensoris carpi ulnaris [TA]). SYN: vaginae tendinum carpalium dorsalium [TA].
- dural s. an extension of the dura mater that ensheathes the roots of spinal nerves or, more particularly, the vagina externa nervi optici.
- fascial s. of eyeball [TA] a condensation of connective tissue on the outer aspect of the sclera from which it is separated by a narrow cleftlike episcleral space; the s. is attached to the sclera near the sclerocorneal junction and blends with the fascia of the extraocular muscles. SYN: vagina bulbi [TA], capsula bulbi, eye capsule, fascia bulbi, s. of eyeball, Tenon capsule, vagina oculi.
- femoral s. the fascia enclosing the femoral vessels, formed by the transversalis fascia anteriorly and the iliac fascia posteriorly; two septa divide the s. into three compartments, the lateral of which contains the femoral artery and the femoral branch of the genitofemoral nerve, the middle contains the femoral vein, and the medial is the femoral canal. SYN: crural s., infundibuliform s..
- fenestrated s. a s. with a window cut in the tip or lateral convexity, through which special cutting instruments can be passed.
- fibrous sheaths fibrous tendon s., fibrous sheaths of digits of hand, fibrous digital sheaths of toes.
- fibrous digital sheaths of toes [TA] fibrous sheaths of the toes, the tubular fibrous layer enclosing the synovial s. and the tendons of the long and short flexors of the toes and the flexor hallucis longus in the digits; they are composed of annular and cruciform parts. SYN: vaginae fibrosae digitorum pedis [TA], fibrous digital sheaths of foot.
- fibrous sheaths of digits of hand [TA] fibrous sheaths of the digits of the hand, the tubular fibrous layers that enclose the synovial sheaths and the superficial and deep flexor tendons and the tendon of the flexor pollicis longus in their passage along their respective digits; they are composed of annular and cruciform parts. SYN: vaginae fibrosae digitorum manus [TA], fibrous digital sheaths of hand.
- fibrous tendon s. [TA] fibrous s. of a tendon. SYN: stratum fibrosum vaginae tendinis, vagina fibrosa tendinis.
- fibular tarsal tendinous sheaths [TA] synovial tendon sheaths of flexor tendons enabling movement of tendons posterior to the lateral malleolus and across tarsal bones, passing deep to the fibular retinacula; includes (1) the common tendinous s. of fibulares (peronei) muscles [TA] (vagina communis tendineum musculorum fibularum (peroneum) [TA]); and (2) the plantar tendinous s. of fibularis (peroneus) (muscle) [TA]) (vagina plantaris tendinis musculi fibularis (peronei) longi [TA]). SYN: vaginae tendinum tarsales fibulares [TA].
- Henle s. SYN: endoneurium.
- Hertwig s. the merged outer and inner epithelial layers of the enamel organ which extends beyond the region of the anatomical crown and initiates formation of dentin in the root of a developing tooth; it atrophies as the root is formed, and any of the cells that persist are called Malassez epithelial rests.
- infundibuliform s. SYN: femoral s..
- inner s. of optic nerve [TA] the innermost s. around the optic nerve, continuous with the leptomeninges (pia-arachnoid) and including a cerebrospinal fluid-filled intervaginal space, continuous with the subarachnoid space. SYN: vagina interna nervi optici [TA], internal s. of optic nerve.
- intertubercular tendon s. [TA] the extension of the synovial membrane of the shoulder joint downward in the intertubercular groove to surround the tendon of the long head of the biceps. SYN: vagina tendinis intertubercularis [TA].
- s. of Key and Retzius SYN: endoneurium.
- microfilarial s. the membrane surrounding the embryos of certain blood-borne microfilariae, such as Wuchereria, Brugia, and Loa of humans; thought to be derived from the vitelline membrane.
- mitochondrial s. the spirally arranged mitochondria in the middle piece of a spermatozoon; provides energy for the movement of the tail.
- myelin s. the lipoproteinaceous envelope in vertebrates surrounding most axons of more than 0.5-μm diameter; it consists of a double plasma membrane wound tightly around the axon in a variable number of turns, and supplied by oligodendroglia cells (in the brain and spinal cord) or Schwann cells (in peripheral nerves); unwound, the double membrane would appear as a sheetlike cell expansion that is empty of cytoplasm but for a few narrow cytoplasmic strands corresponding to apparent interruptions of the regular myelin structure, the incisures of Schmidt-Lanterman; the myelin s. of each axon is composed of a fairly regular longitudinal sequence of segments, each corresponding to the length of s. supplied by a single oligodendroglia or Schwann cell; in the short interval between each two neighboring segments, the nodes of Ranvier, the axon is unmyelinated even though enclosed by complex finger-like plasmatic expansions of the neighboring oligodendroglia or Schwann cells. SYN: medullary s..
- neurovascular s. fibrous tissue enveloping and binding together arteries, their accompanying veins (venae comitantes) and nerves that run together; often it is merely the adventitious tissue of the neurovascular structures, but may be highly developed as a distinct fascial layer ( e.g., in the case of the carotid or axillary sheaths).
- outer s. of optic nerve [TA] the outer s. around the optic nerve, continuous with the dura mater. SYN: vagina externa nervi optici [TA], dural s. of optic nerve, external s. of optic nerve.
- palmar carpal tendinous sheaths [TA] three synovial tendon sheaths that allow movement of tendons across the anterior aspect of the wrist, deep to or within the flexor retinaculum; they are the: (1) tendinous s. of flexor pollicis longus (muscle) [TA] (vagina tendinis musculi flexoris pollicis longi [TA]); (2) tendinous s. of flexor carpi radialis (muscle) [TA] (vagina tendinis musculi flexoris carpi radialis [TA]); and (3) common flexor s. [TA] (vagina communis tendineum musculorum flexorum [TA]). SYN: vaginae tendinum carpales palmares [TA].
- periarterial lymphatic s. (PALS) the accumulation of lymphocytes investing the central arteries of the spleen and comprising the white pulp.
- plantar tendon s. of fibularis longus muscle [TA] the synovial s. surrounding the tendon of the peroneus longus in its course across the sole of the foot. SYN: vagina tendinis musculi fibularis longi plantaris [TA], plantar tendon s. of peroneus longus muscle, vagina tendinis musculi peronei longi plantaris.
- prostatic s. loose fibrous, partly vascular enclosure of the prostate and its dense (true) fibrous capsule; it is continuous inferiorly with the superior fascia of the urogenital diaphragm and posteriorly becomes part of the rectovesical septum; it contains the prostatic venous plexus.
- rectus s. [TA] s. of the rectus abdominis, formed by the aponeuroses of the three anterolateral muscles of the abdominal wall that split to enclose the rectus and fuse medially to form the linea alba; it consists of an anterior lamina and a posterior lamina, the latter being absent below the arcuate line. SEE ALSO: aponeurosis of external oblique muscle, aponeurosis of internal oblique muscle. SYN: vagina musculi recti abdominis [TA].
- resectoscope s. an operative s. through which transurethral electroresection of bladder tumors or prostate gland can be performed.
- root s. one of the epidermic layers of the hair follicle : external root s. is continuous with the stratum basale and stratum spinosum of the epidermis; internal root s. comprises the cuticle of the internal roots, Huxley layer, and Henle layer.
- Rouget-Neumann s. the amorphous ground substance between an osteocyte and the lacunar or canalicular wall.
- Scarpa s. SYN: cremasteric fascia.
- s. of Schwann SYN: neurilemma.
- s. of styloid process [TA] a crest of bone (edge of the tympanic portion of the temporal bone) running from the front and medial side of the mastoid process to the spine of the sphenoid; it splits to ensheath the base of the styloid process. SYN: vagina processus styloidei [TA], vaginal process.
- synovial s. [TA] See synovial tendon s., vagina synovialis trochleae, synovial sheaths of digits of hand, synovial sheaths of toes. SYN: vagina synovialis [TA].
- synovial sheaths of digits of hand [TA] the synovial sheaths that enclose the flexor tendons of the fingers and line the inside of the fibrous tendon sheaths. SYN: vaginae synoviales digitorum manus [TA].
- synovial tendon s. [TA] a s. of synovial membrane enveloping certain of the tendons; it contains a small amount of synovial fluid. SYN: vagina synovialis tendinis [TA], mucous s. of tendon, theca tendinis, vagina mucosa tendinis, vaginal synovial membrane.
- synovial sheaths of toes [TA] similar in structure to the corresponding sheaths of the hand. SYN: vaginae tendinum digitorum pedis [TA], synovial sheaths of digits of foot.
- tendinous s. of abductor pollicis longus and extensor pollicis brevis muscles [TA] the dorsal carpal synovial tendinous s. lining the compartment of the extensor retinaculum that contains the abductor pollicis longus and extensor pollicis brevis tendons. SYN: vagina tendinum musculorum abductoris longi et extensoris brevis pollicis [TA].
- tendinous s. of extensor carpi radialis muscles [TA] the dorsal carpal synovial tendon s. lining the compartment of the extensor retinaculum containing the tendons of the extensor carpi radialis longus and brevis muscles. SYN: vagina tendinum musculorum extensorum carpi radialium [TA].
- tendinous s. of extensor carpi ulnaris muscle [TA] the dorsal carpal synovial tendon s. surrounding the tendon of the extensor carpi ulnaris in its course deep to the extensor retinaculum. SYN: vagina tendinis musculi extensoris carpi ulnaris [TA], peritenon.
- tendinous s. of extensor digiti minimi muscle [TA] the dorsal carpal synovial tendon s. surrounding the tendon of the extensor digiti minimi in its passage deep to the extensor retinaculum. SYN: vagina tendinis musculi extensoris digiti minimi [TA].
- tendinous s. of extensor digitorum and extensor indicis muscles [TA] the dorsal carpal synovial tendon s. that surrounds the four tendons of the extensor digitorum muscle and the tendon of the extensor indicis deep to the extensor retinaculum. SYN: vagina tendinum musculorum extensoris digitorum et extensoris indicis [TA].
- tendinous s. of extensor digitorum longus muscle of foot [TA] the anterior tarsal synovial tendon s. that surrounds the tendons of the extensor digitorum longus muscle and the peroneus tertius in their passage across the ankle. SYN: vagina tendinum musculi extensoris digitorum pedis longi [TA].
- tendinous s. of extensor hallucis longus muscle [TA] the anterior tarsal synovial tendon s. that surrounds the tendon of the extensor hallucis longus in its passage across the ankle. SYN: vagina tendinis musculi extensoris hallucis longi [TA].
- tendinous s. of extensor pollicis longus muscle [TA] the dorsal carpal synovial tendon s. surrounding the extensor pollicis longus tendon in its passage deep to the extensor retinaculum. SYN: vagina tendinis musculi extensoris pollicis longi [TA].
- tendinous s. of flexor carpi radialis muscle [TA] the palmar carpal synovial tendon s. enclosing the tendon of the flexor carpi radialis as it crosses the wrist. SYN: vagina tendinis musculi flexoris carpi radialis [TA].
- tendinous s. of flexor digitorum longus muscle (of foot) [TA] the tibial tarsal synovial tendon s. that envelops the flexor digitorum longus tendons as they pass into the foot deep to the flexor retinaculum. SYN: vagina tendinum musculi flexoris digitorum pedis longi [TA].
- tendinous s. of flexor hallucis longus muscle [TA] the tibial tarsal synovial tendon s. that envelops the tendon of the flexor hallucis longus as it passes into the foot deep to the flexor retinaculum. SYN: vagina tendinis musculi flexoris hallucis longi [TA].
- tendinous s. of flexor pollicis longus muscle [TA] the palmar carpal synovial tendon s. that envelops the tendon of the flexor pollicis longus in its course through the carpal canal; it is continuous with the digital s. of the thumb, the two generally being considered as one s.. SYN: vagina tendinis musculi flexoris pollicis longi [TA], radial bursa.
- tendinous s. of superior oblique muscle [TA] the synovial s. enclosing the tendon of the superior oblique muscle as it passes through the trochlea. SYN: vagina tendinis musculi obliqui superioris [TA], synovial trochlear bursa, trochlear synovial bursa, vagina synovialis trochleae.
- tendinous s. of tibialis anterior muscle [TA] the anterior tarsal synovial tendon s., deep to the extensor retinaculum, that surrounds the tendon of the tibialis anterior as it crosses the ankle. SYN: vagina tendinis musculi tibialis anterioris [TA].
- tendinous s. of tibialis posterior muscle [TA] the tibial tarsal synovial tendon s. surrounding the tendon of the tibialis posterior as it passes into the foot deep to the flexor retinaculum. SYN: vagina tendinis musculi tibialis posterioris [TA].
- s. of thyroid gland covering of the thyroid gland external to its capsule formed by a splitting of the pretracheal layer of deep cervical fascia at the gland's posterior border; the anterior lamina covers the gland anterolaterally, attaching to the arch of the cricoid cartilage superior to the isthmus of the gland (causing it to move with the trachea during elevation/depression of the larynx); the posterior lamina passes posterior to the esophagus to blend with the buccopharyngeal fascia; inferiorly, the s. extends along the inferior thyroid veins to open into the superior mediastinum (hence, expansion of the thyroid, as by goiter, can take this direction).
- tibial tarsal tendinous sheaths [TA] synovial tendon sheaths that allow movement of tendons across the medial side of the tarsal bones, deep to flexor retinaculum; included are (1) the tendinous s. (vagina tendinis/tendinum musculi...) of flexor digitorum longus (muscle) [TA] (...flexoris digitorum longi [TA]); (2) the tibialis posterior (muscle) [TA] (...tibialis posterioris [TA]); and (3) the flexor hallucis longus (muscle) [TA] (...flexoris hallucis longi [TA]). SYN: vaginae tendinum tarsales tibialis [TA].
- vascular sheaths fibrous envelopes ensheathing the arteries with their accompanying veins and sometimes nerves as well. SYN: sheaths of vessels, vaginae vasorum.
- sheaths of vessels SYN: vascular sheaths.
- Waldeyer s. the tubular space between the bladder wall and the intramural portion of the ureter as it courses obliquely through this structure; actually a space and not a true s.. SYN: Waldeyer space.
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1) an investing cover or case of a plant or animal body or body part: as
a) the tubular fold of skin into which the penis of many mammals is retracted
b) the connective tissue of an organ or part that binds together its component elements and holds it in place
2) CONDOM (1)
sheathed adj
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n.
1. (in anatomy) the layer of connective tissue that envelops structures such as nerves, arteries, tendons, and muscles.
2. a condom.
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(shēth) [L. vagina; Gr. thēkē] a tubular structure enclosing or surrounding some organ or part.Medical dictionary. 2011.