| 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) |
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| internal spiral sulcus | A concavity in the floor of the cochlear duct formed by the overhanging labium vestibulare. Synonym: sulcus spiralis internus. (05 Mar 2000) |
| internal squint | Cross-eyed. (27 Sep 1997) |
| internal strabismus | An obsolete term for esotropia (05 Mar 2000) |
| internal surface | The internal concave surface of either the frontal or the parietal bone. Synonym: facies interna. (05 Mar 2000) |
| internal surface of frontal bone | The surface of the frontal bone that contributes to the wall of the cranial cavity. Synonym: facies interna ossis frontalis. (05 Mar 2000) |
| internal surface of parietal bone | The concave surface of the parietal bone forming part of the wall of the cranial cavity. Synonym: facies interna ossis parietalis. (05 Mar 2000) |
| internal traction | A pulling force created by using one of the cranial bones, above the point of fracture, for anchorage. (05 Mar 2000) |
| internal urethral opening | The internal opening or orifice of the urethra, at the anterior and inferior angle of the trigone. Synonym: ostium urethrae internum, internal urethral opening. (05 Mar 2000) |
| internal urethral orifice | The internal opening or orifice of the urethra, at the anterior and inferior angle of the trigone. Synonym: ostium urethrae internum, internal urethral opening. (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) |
| opening of internal acoustic meatus | The inner opening of the internal acoustic meatus on the posterior surface of the petrous part of the temporal bone. Synonym: porus acusticus internus, internal acoustic foramen, internal acoustic pore, auditory pore, internal auditory foramen, orifice of internal acoustic meatus. (05 Mar 2000) |
| orifice of internal acoustic meatus | The inner opening of the internal acoustic meatus on the posterior surface of the petrous part of the temporal bone. Synonym: porus acusticus internus, internal acoustic foramen, internal acoustic pore, auditory pore, internal auditory foramen, orifice of internal acoustic meatus. (05 Mar 2000) |
| transverse crest of internal acoustic meatus | A horizontal ridge that divides the fundus of the internal acoustic meatus into a superior and an inferior area. In the former are the introitus of the facial canal and openings for the branches of the vestibular nerve to the utricle and to the ampullae of the anterior and lateral saemicircular canals. In the latter are openings for the cochlear nerve, and for branches of the vestibular nerve to the saccule and to the ampulla of the posterior saemicircular canal. Synonym: crista transversa, falciform crest, transverse crest. (05 Mar 2000) |
| lamina internal ossium cranii | The inner table of one of the cranial bones; it is more compact and harder than the outer table. Synonym: lamina internal ossium cranii. (05 Mar 2000) |