| inferior oesophageal sphincter | A sphincter supposedly present at the oesophagogastric junction; this is in fact an extrinsic sphincter formed by the surrounding musculature of the oesophageal hiagus of the right crus of the diaphragm; causes a normally-occuring constriction at the oesophagogastric junction observable with a barium swallow. Synonym: sphincter constrictor cardiae. (05 Mar 2000) |
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| internal anal sphincter | <anatomy> A smooth muscle ring, formed by an increase of the circular fibres of the rectum, situated at the upper end of the anal canal, internal to the outer voluntary external anal sphincter. This sphincter is maximally-contracted when the rectal ampulla is at rest -empty or relaxed to accommodate a distending faecal mass. It is inhibited with filling of the ampulla, increased distension and peristalsis. Synonym: musculus sphincter ani internus, internal sphincter muscle of anus. (05 Mar 2000) |
| internal sphincter muscle of anus | <anatomy> A smooth muscle ring, formed by an increase of the circular fibres of the rectum, situated at the upper end of the anal canal, internal to the outer voluntary external anal sphincter. This sphincter is maximally-contracted when the rectal ampulla is at rest -empty or relaxed to accommodate a distending faecal mass. It is inhibited with filling of the ampulla, increased distension and peristalsis. Synonym: musculus sphincter ani internus, internal sphincter muscle of anus. (05 Mar 2000) |
| internal urethral sphincter | The complete collar of smooth muscle cells of the neck of the urinary bladder which extend distally to surround the preprostatic sportion of the male urethra. There is not a comparable structure in the neck of the femoral bladder; the internal urethral sphincter may exist to prevent reflux of semen into bladder. Synonym: annulus urethralis, internal urethral sphincter, musculus sphincter vesicae, preprostate urethral sphincter, proximal urethral sphincter, sphincter muscle of urinary bladder. (05 Mar 2000) |
| intrinsic sphincter | A thickening of the circular fibres of the muscular coat of an organ. (05 Mar 2000) |
| O'Beirne's sphincter | <anatomy> A circular band of muscular fibres at the recto sigmoid junction. Synonym: O'Beirne's sphincter, O'Beirne's valve, pelvirectal sphincter. (05 Mar 2000) |
| oddi's sphincter | An annular sheath of muscle that invests the bile duct within the wall of the duodenum. (12 Dec 1998) |
| ostial sphincter | A thickening of circular muscular fibres at the level of an orifice. (05 Mar 2000) |
| external anal sphincter | A fusiform ring of striated muscular fibres surrounding the anus, attached posteriorly to the coccyx and anteriorly to the central tendon of the perineum; it is subdivided, often indistinctly, into a subcutaneous part, a superficial part and a deep part for descriptive purposes. Synonym: musculus sphincter ani externus, external sphincter muscle of anus. (05 Mar 2000) |
| external sphincter muscle of anus | A fusiform ring of striated muscular fibres surrounding the anus, attached posteriorly to the coccyx and anteriorly to the central tendon of the perineum; it is subdivided, often indistinctly, into a subcutaneous part, a superficial part and a deep part for descriptive purposes. Synonym: musculus sphincter ani externus, external sphincter muscle of anus. (05 Mar 2000) |
| external urethral sphincter | Origin, ramus of pubis; insertion, with fellow in median raphe behind and in front of urethra; action, constricts membranous urethra; nerve supply, pudendal. Synonym: musculus sphincter urethrae, external urethral sphincter, Guthrie's muscle, musculus compressor urethrae, musculus constrictor urethrae, musculus sphincter urethrae membranaceae, sphincter muscle of urethra, Wilson's muscle. (05 Mar 2000) |
| extrinsic sphincter | A sphincter provided by circular muscular fibres extraneous to the organ. (05 Mar 2000) |
| unicanalicular sphincter | A sphincter limited to one visceral canal or tube. (05 Mar 2000) |
| urinary sphincter, artificial | An artifical implanted device, usually in the form of an inflatable silicone cuff, inserted in or around the bladder neck in the surgical treatment of urinary incontinence caused by sphincter weakness. Often it is placed around the bulbous urethra in adult males. The artificial urinary sphincter is considered an alternative to urinary diversion. (12 Dec 1998) |
| first duodenal sphincter | The sphincter supposedly located at the level of the aboral extremity of the duodenal bulb. (05 Mar 2000) |