A muscle that encircles a duct, tube or orifice in such a way that its contraction constricts the lumen or orifice; it is the closing component of a pylorus (the outer component is the s. dilator).musculus sphincter [NA] , sphincter muscle; [G. sphinkter, a band or lace]
anatomical s.an accumulation of muscular circular fibers or specially arranged oblique fibers the function of which is to reduce partially or totally the lumen of a tube, the orifice of an organ, or the cavity of a viscus; the closing component of a pylorus.
s. angula´ris, angular s.thickening of the circular muscular layer forming a proposed intermediate s. 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.antral s., midgastric transverse s., s. antri, s. intermedius, s. of antrum, s. of gastric antrum;
s. a´ni, anal s. See external anal s., internal anal s.
s. a´ni ter´tiusthe third s. of the anorectum, a physiological s. at the sigmoidorectal junction.
annular s.a short thickening of circular muscular fibers, similar to a ring; a ring-shaped s. as opposed to a segmental s.
antral s.s. angularis
s. an´tris. angularis
s. of antrums. angularis
artificial s.a s. produced by surgical procedures to reduce speed of flow in the digestive system or to maintain continence of the intestine.
basal s.the thickening of the circular muscular coat at the base of the ileal papilla at the terminal ileum.sphincteroid tract of ileum;
bicanalicular s.a s. encircling two canals, such as the terminal portions of the common bile duct and the main pancreatic duct.
Boyden's s.s. of common bile duct
canalicular s.a s. located somewhere along the course of an organ, a tube, or a duct, as opposed to ostial s.
choledochal s.s. of common bile duct
colic s.one of the physiological s.'s of the colon.
s. of common bile ductsmooth 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.musculus sphincter ductus choledochi [NA] , Boyden's s., choledochal s., sphincter muscle of common bile duct;
s. constric´tor car´diaeinferior esophageal s
duodenal s.one of the physiological s.'s described in the duodenum.
duodenojejunal s.the s. supposedly present at the duodenojejunal flexure.
external anal s.a fusiform ring of striated muscular fibers 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.musculus sphincter ani externus [NA] , external sphincter muscle of anus;
external urethral s.s. urethrae
extrinsic s.a s. provided by circular muscular fibers extraneous to the organ.
first duodenal s.the s. supposedly located at the level of the aboral extremity of the duodenal bulb.
functional s.physiological s
s. of gastric antrums. angularis
Glisson's s.s. of hepatopancreatic ampulla
s. of hepatic flexure of colonphysiological s. at the level of the right colic flexure.
hepatopancreatic s.s. of hepatopancreatic ampulla
s. of hepatopancreatic ampullathe smooth muscle sphincter of the hepatopancreatic ampulla within the duodenal papilla.musculus sphincter ampullae hepatopancreaticae [NA] , Glisson's s., hepatopancreatic s., Oddi's s;
Hyrtl's s.a band, generally incomplete, of circular muscular fibers in the rectum about 10 cm above the anus (upper rectal ampulla). See Nélaton's s.
ileal s.a thickening of circular musculature at the free margin of the ileal papilla.ileocecocolic s., marginal s., operculum ilei, Varolius' s;
ileocecocolic s.ileal s
iliopelvic s.midsigmoid s
inferior esophageal s.a s. supposedly present at the esophagogastric junction; this is in fact an extrinsic sphincter formed by the surrounding musculature of the esophageal hiagus of the right crus of the diaphragm; causes a normally-occuring constriction at the esophagogastric junction observable with a barium swallow.s. constrictor cardiae;
s. intermediuss. angularis
internal anal s.a smooth muscle ring, formed by an increase of the circular fibers 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 fecal mass. It is inhibited with filling of the ampulla, increased distension and peristalsis.musculus sphincter ani internus [NA] , internal sphincter muscle of anus;
internal urethral s.s. vesicae
intrinsic s.a thickening of the circular fibers of the muscular coat of an organ.
lower esophageal s. (LES) musculature of the gastroesophageal junction that is tonically active except during swallowing.
macroscopic s.a s. visible to the naked eye.
marginal s.ileal s
mediocolic s.a physiological s. located midway in the ascending colon.
microscopic s.a s. visible only under the microscope.
midgastric transverse s.s. angularis
midsigmoid s.the physiological s. midway in the sigmoid colon.iliopelvic s;
myovascular s.a s. having a muscular and a vascular (usually venous) component. See myovenous s.
myovenous s.a s. having a muscular and a venous component, e.g., at the pharyngoesophageal junction and anal canal.
Nélaton's s. See transverse rectal folds, under fold.Nélaton's fibers;
O'Beirne's s.rectosigmoid s
s. oc´uliorbicularis oculi muscle
Oddi's s.s. of hepatopancreatic ampulla
s. o´risorbicularis oris muscle
ostial s.a thickening of circular muscular fibers at the level of an orifice.
palatopharyngeal s.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.pharyngeal ridge, s. of the pharyngeal isthmus, velopharyngeal s;
pancreatic s.s. of pancreatic duct
s. of pancreatic ductsmooth muscle sphincter of the main pancreatic duct immediately proximal to the hepatoduodenal, ampulla.musculus sphincter ductus pancreatici, pancreatic s., sphincter muscle of pancreatic duct;
pathologic s.a thickening of circular musculature caused by disease.
pelvirectal s.rectosigmoid s
s. of the pharyngeal isthmuspalatopharyngeal s
physiological s.a section of a tubular structure that acts as if it has a band of circular muscle to constrict it, although no such specialized structure can be found on morphological examination.functional s., radiological s;
postpyloric s.the duodenal portion of the s. or closing mechanism of the gastroduodenal pylorus.
prepapillary s.a s. of duodenum described in the location oral to the major duodenal papilla.
preprostate urethral s.s. vesicae
prepyloric s.a band of circular muscular fibers in the wall of the stomach near the gastroduodenal pylorus.
proximal urethral s.s. vesicae
s. pupil´laea ring of smooth muscle fibers surrounding the pupillary border of the iris.musculus sphincter pupillae [NA] , sphincter muscle of pupil;
pyloric s.a thickening of the circular layer of the gastric musculature encircling the gastroduodenal junction.musculus sphincter pylori [NA] , sphincter muscle of pylorus;
radiological s.physiological s
rectosigmoid s.a circular band of muscular fibers at the recto sigmoid junction.O'Beirne's s., O'Beirne's valve, pelvirectal s;
segmental s.a s. of a segment of an organ, a tube, or a canal, and longer than an annular s.
smooth muscular s.lissosphincter
striated muscular s.rhabdosphincter
superior esophageal s.cricopharyngeus muscle See inferior constrictor muscle of pharynx.
s. of third portion of duodenuma physiological s. supposedly located at the horizontal (inferior) portion of the duodenum.
unicanalicular s.a s. limited to one visceral canal or tube.
s. ure´thraeorigin, ramus of pubis; insertion, with fellow in median raphe behind and in front of urethra; action, constricts membranous urethra; nerve supply, pudendal.musculus sphincter urethrae [NA] , external urethral s., Guthrie's muscle, musculus compressor urethrae, musculus constrictor urethrae, musculus sphincter urethrae membranaceae, sphincter muscle of urethra, Wilson's muscle (1) ;
s. vagi´nae 1. bulbocavernosus muscle 2. deep transverse perineal muscle
Varolius' s.ileal s
velopharyngeal s.palatopharyngeal s
s. vesi´caethe 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 s. may exist to prevent reflux of semen into bladder.annulus urethralis, internal urethral s., musculus sphincter vesicae, preprostate urethral s., proximal urethral s., sphincter muscle of urinary bladder;
s. vesi´cae biliaristhe s. of the gallbladder, at the transition between the neck of the gallbladder and the cystic duct.
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