| 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) |
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| 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) |
| sphincter pupillae | A ring of smooth muscle fibres surrounding the pupillary border of the iris. Synonym: musculus sphincter pupillae, sphincter muscle of pupil. (05 Mar 2000) |
| sphincter urethrae | 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 vaginae | <anatomy> In the male: origin, the perineal membrane fascia on the dorsum of the bulb of the penis; insertion, central tendon of the perineum and the median raphe on the free surface of the bulb; action, constricts bulbous urethra when attempting to expel last drops following urination, or spasmodically with ejaculation to expel semen. In the female: origin, the dorsum of the clitoris, the corpus cavernosum, and the perineal membrane; insertion, central tendon of the perineum; action, acts as a weak sphincter of the vagina; when developed, is a part of "cross-member musculature" of pelvic floor which resists prolapse of pelvic viscera. Nerve supply, pudendal (deep perineal branch). Synonym: musculus bulbospongiosus, musculus bulbocavernosus, musculus ejaculator seminis, musculus sphincter vaginae, sphincter vaginae. (05 Mar 2000) |
| sphincter vesicae | 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 vesicae biliaris | The sphincter of the gallbladder, at the transition between the neck of the gallbladder and the cystic duct. (05 Mar 2000) |
| Nelaton's sphincter | See: transverse rectal folds. Synonym: Nelaton's fibres. (05 Mar 2000) |
| striated muscular sphincter | A sphincter made up of striated musculature. Synonym: striated muscular sphincter. Origin: rhabdo-+ G. Sphinkter, sphincter (05 Mar 2000) |
| subcutaneous part of external anal sphincter | pars subcutanea musculi sphincteri ani externi, subcutaneous portion of external anal sphincter |
| subcutaneous portion of external anal sphincter | pars subcutanea musculi sphincteri ani externi, subcutaneous portion of external anal sphincter |
| superficial part of external anal sphincter | superficial part of external anal sphincter |
| superior oesophageal sphincter | <anatomy, muscle> This is the horizontal muscle located at the top of the oesophagus. (13 Nov 1997) |
| deep part of external anal sphincter | deep part of external anal sphincter |