| sphincter muscle of pupil | A ring of smooth muscle fibres surrounding the pupillary border of the iris. Synonym: musculus sphincter pupillae, sphincter muscle of pupil. (05 Mar 2000) |
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| sphincter muscle of pylorus | A thickening of the circular layer of the gastric musculature encircling the gastroduodenal junction. Synonym: musculus sphincter pylori, sphincter muscle of pylorus. (05 Mar 2000) |
| sphincter muscle of urethra | 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) |
| sphincter muscle of urinary bladder | 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) |
| sphincter oculi | <anatomy> Consists of three portions: orbital part, or external portion, which arises from frontal process of maxilla and nasal process of frontal bone, encircles aperture of orbit, and is inserted near origin; palpebral part, or internal portion, which arises from medial palpebral ligament, passes through each eyelid, and is inserted into lateral palpebral raphe; lacrimal part (tensor tarsi muscle, Duverney's or Horner's muscle) arises from posterior lacrimal crest and passes across lacrimal sac to join palpebral portion; action, closes eye, wrinkles forehead vertically; nerve supply, facial. Synonym: musculus orbicularis oculi, musculus orbicularis palpebrarum, orbicular muscle of eye, sphincter oculi. (05 Mar 2000) |
| sphincter of antrum | Angular sphincter, thickening of the circular muscular layer forming a proposed intermediate sphincter at the level of the angular notch of the stomach. While the thickening of the circular muscle may indicate the commencement of the pyloric antrum, true functional sphincteric activity distinct from the other peristaltic contractions of the stomach is not observed although some of these may in fact temporarily close off the antrum from the remainder of the stomach lumen. Synonym: antral sphincter, midgastric transverse sphincter, sphincter antri, sphincter intermedius, sphincter of antrum, sphincter of gastric antrum. (05 Mar 2000) |
| sphincter of common bile duct | Smooth muscle sphincter of the common bile duct immediately proximal to the hepatopancreatic ampulla; it is this sphincter that controls the flow of bile in the duodenum. Synonym: musculus sphincter ductus choledochi, Boyden's sphincter, choledochal sphincter, sphincter muscle of common bile duct. (05 Mar 2000) |
| sphincter of gastric antrum | Angular sphincter, thickening of the circular muscular layer forming a proposed intermediate sphincter at the level of the angular notch of the stomach. While the thickening of the circular muscle may indicate the commencement of the pyloric antrum, true functional sphincteric activity distinct from the other peristaltic contractions of the stomach is not observed although some of these may in fact temporarily close off the antrum from the remainder of the stomach lumen. Synonym: antral sphincter, midgastric transverse sphincter, sphincter antri, sphincter intermedius, sphincter of antrum, sphincter of gastric antrum. (05 Mar 2000) |
| sphincter of hepatic flexure of colon | Physiological sphincter at the level of the right colic flexure. (05 Mar 2000) |
| sphincter of hepatopancreatic ampulla | The smooth muscle sphincter of the hepatopancreatic ampulla within the duodenal papilla. Synonym: musculus sphincter ampullae hepatopancreaticae, Glisson's sphincter, hepatopancreatic sphincter, Oddi's sphincter. (05 Mar 2000) |
| sphincter of Oddi dysfunction | Structural or functional abnormality of the sphincter of Oddi that interferes with bile drainage. Synonym: biliary dyskinesia. (05 Mar 2000) |
| sphincter of pancreatic duct | Smooth muscle sphincter of the main pancreatic duct immediately proximal to the hepatoduodenal, ampulla. Synonym: musculus sphincter ductus pancreatici, pancreatic sphincter, sphincter muscle of pancreatic duct. (05 Mar 2000) |
| sphincter of the pharyngeal isthmus | A constant band of the superior pharyngeal constrictor muscle which sweeps posteriorly from the anterolateral part of the superior surface of the palatine aponeurosis. It creates a visible ridge when the superior constrictor is contracted, meeting the elevated soft palate to seal off the pharyngeal isthmus during swallowing. Synonym: pharyngeal ridge, sphincter of the pharyngeal isthmus, velopharyngeal sphincter. (05 Mar 2000) |
| sphincter of third portion of duodenum | A physiological sphincter supposedly located at the horizontal (inferior) portion of the duodenum. (05 Mar 2000) |
| sphincter oris | <anatomy, muscle> Origin, by nasolabial band from septum of the nose, by superior incisive bundle from incisor fossa of maxilla, by inferior incisive bundle from lower jaw each side of symphysis; insertion, fibres surround mouth between skin and mucous membrane of lips and cheeks, and are blended with other muscles; action, closes lips; nerve supply, facial. Synonym: musculus orbicularis oris, musculus sphincter oris, orbicular muscle of mouth, sphincter oris. (05 Mar 2000) |