| 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) |
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| 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 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) |
| first duodenal sphincter | The sphincter supposedly located at the level of the aboral extremity of the duodenal bulb. (05 Mar 2000) |
| functional sphincter | A section of a tubular structure that acts as if it has a band of circular muscle to constrict it, although no such specialised structure can be found on morphological examination. Synonym: functional sphincter, radiological sphincter. (05 Mar 2000) |
| lower oesophageal sphincter | <anatomy> A muscular sphincter located at the junction of the oesophagus and the stomach. On closure the lower oesophageal sphincter prevents the back wash (reflux) of stomach acid into the oesophagus where it may damage the mucosa. See: gastrooesophageal reflux disease. (16 Mar 1998) |
| abdominal external oblique muscle | <anatomy, muscle> Origin, fifth to twelfth ribs; insertion, anterior half of lateral lip of iliac crest, inguinal ligament, and anterior layer of the rectus sheath; action, diminishes capacity of abdomen, draws thorax downward; nerve supply, thoracoabdominal nerves. Synonym: musculus obliquus externus abdominis, abdominal external oblique muscle. (05 Mar 2000) |
| abdominal internal oblique muscle | <anatomy, muscle> Origin, iliac fascia deep to lateral part of inguinal ligament, anterior half of crest of ilium, and lumbar fascia; insertion, tenth to twelfth ribs and sheath of rectus; some of the fibres from inguinal ligament terminate in the conjoint tendon; action, diminishes capacity of abdomen, flexes lumbar vertebral column (bends thorax forward); nerve supply, lower thoracic. Synonym: musculus obliquus internus abdominis, abdominal internal oblique muscle. (05 Mar 2000) |
| abdominal muscle deficiency syndrome | <syndrome> Congenital absence (partial or complete) of abdominal muscles, in which the outline of the intestines is visible through the protruding abdominal wall; in males, genitourinary anomalies (urinary tract dilation and cryptorchidism) are also found; genetics unclear. (05 Mar 2000) |
| abductor digiti minimi muscle of foot | Origin, lateral and medial processes of calcanean tuberosity; insertion, lateral side of proximal phalanx of fifth toe; action, abducts and flexes little toe; nerve supply, lateral plantar nerve. Synonym: musculus abductor digiti minimi pedis, abductor muscle of little toe, musculus abductor digiti quinti. (05 Mar 2000) |
| abductor digiti minimi muscle of hand | Origin, pisiform bone and pisohamate ligament; insertion, medial side of base of proximal phalanx of the little finger; action, abducts and flexes little finger; nerve supply, ulnar. Synonym: musculus abductor digiti minimi manus, abductor muscle of little finger, musculus abductor digiti quinti. (05 Mar 2000) |