| external sheath of optic nerve | <anatomy, nerve> The outer sheath around the optic nerve, continuous with the dura mater. Synonym: vagina externa nervi optici, dural sheath of optic nerve. (05 Mar 2000) |
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| external spermatic artery | <anatomy, artery> Origin, inferior epigastric; distribution, coverings of spermatic cord; anastomoses, external pudendal, spermatic, and perineal arteria. Synonym: arteria cremasterica, external spermatic artery. (05 Mar 2000) |
| external spermatic fascia | The outer fascial covering of the spermatic cord; it is continuous at the superficial inguinal ring with the fascia covering the external oblique muscle. See: aponeurosis of external abdominal oblique muscle. Synonym: fascia spermatica externa. (05 Mar 2000) |
| external spermatic nerve | <anatomy, nerve> Branch of genitofemoral nerve distributed to skin of anterior scrotum (male) or labia majora (female) and adjacent thigh and supplying a motor branch to the cremaster muscle. Usually passes through deep inguinal ring and canal. Synonym: ramus genitalis nervi genitofemoralis, external spermatic nerve, nervus spermaticus externus. (05 Mar 2000) |
| external sphincter muscle of anus | 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 sphincterotomy | Transurethral incision of external urethral sphincter. (05 Mar 2000) |
| external spiral sulcus | A concavity in the outer wall of the cochlear duct between the prominentia spiralis and the spiral organ. Synonym: sulcus spiralis externus. (05 Mar 2000) |
| external squint | <clinical sign> The outward or temporal deviation of an eye. (27 Sep 1997) |
| external strabismus | An obsolete term for exotropia. (05 Mar 2000) |
| external surface | The outer convex surface of either the frontal or the parietal bone. Synonym: facies externa. (05 Mar 2000) |
| external surface of parietal bone | The convex outer surface of the parietal bone. Synonym: facies externa ossis parietalis. (05 Mar 2000) |
| external traction | A pulling force created by using fixed anchorage (e.g., a headcap or bed frame) outside the oral cavity; principally used in the management of midfacial fractures. (05 Mar 2000) |
| external urethral orifice | The slitlike opening of the urethra in the glans penis, the external orifice of the urethra (in the female) in the vestibule, usually upon a slight elevation, the papilla urethrae. Synonym: ostium urethrae externum, external opening of urethra, meatus urinarius, orificium urethrae externum. (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) |
| external wall of cochlear duct | The wall that faces the outer side of the cochlea. Synonym: paries externus ductus cochlearis. (05 Mar 2000) |