| external anal sphincter | 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) |
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| external aperture of cochlear canaliculus | The external opening of the cochlear aqueduct on the temporal bone medial to the jugular fossa. Synonym: apertura externa canaliculi cochleae. (05 Mar 2000) |
| external aperture of vestibular aqueduct | The external opening of the vestibular aqueduct on the posterior surface of the petrous part of the temporal bone near the groove for the sigmoid sinus. Synonym: apertura externa aqueductus vestibuli. (05 Mar 2000) |
| external arcuate fibres | They include: 1) dorsal external arcuate fibres that arise from cells in the accessory or lateral cuneate nucleus and pass to the cerebellum; 2) ventral external arcuate fibres that arise from the arcuate nuclei at the base of the medulla oblongata and pass around the lateral surface of the medulla; both enter the cerebellum as components of the restiform portion of the inferior cerebellar peduncle. Synonym: fibrae arcuatae externae. (05 Mar 2000) |
| external artery of nose | Origin, ophthalmic; external artery of the nose; distribution, skin of side of root of nose; anastomoses, angular artery. Synonym: arteria dorsalis nasi, arteria nasi externa, dorsal artery of nose, external artery of nose. (05 Mar 2000) |
| external auditory foramen | The orifice of the external acoustic meatus in the tympanic portion of the temporal bone. Synonym: porus acusticus externus, external acoustic foramen, external acoustic pore, external auditory pore, external auditory foramen, orifice of external acoustic meatus. (05 Mar 2000) |
| external auditory meatus | The passage leading inward through the tympanic portion of the temporal bone, from the auricle to the tympanic membrane; it consists of a bony (inner) portion and a fibrocartilaginous (outer) portion, the cartilaginous external acoustic meatus. Synonym: meatus acusticus externus, acoustic meatus, antrum auris, auditory canal, external auditory meatus. (05 Mar 2000) |
| external axis of eye | That part of the optic axis from the midpoint of anterior surface of the cornea to the posterior surface of the posterior pole of the external surface of the sclera. Synonym: axis bulbi externus. (05 Mar 2000) |
| external base of skull | External aspect of the base of skull Synonym: norma basilaris, basis cranii externa, norma inferior, norma ventralis. (05 Mar 2000) |
| external branch of accessory nerve | <anatomy, nerve> Portion of the accessory nerve trunk which exits independently from the jugular foramen, carrying fibres from the spinal root of the accessory nerve to the sternocleidomastoid and trapezius muscle. (05 Mar 2000) |
| external branch of superior laryngeal nerve | <anatomy, nerve> Terminal branch of superior laryngeal nerve (with internal laryngeal nerve) supplying motor innervation to cricothyroid muscle. Synonym: ramus externus nervi laryngei superioris. (05 Mar 2000) |
| external canthus | The angle formed by the junction of the lateral parts of the upper and lower eyelids. Synonym: angulus oculi lateralis, angulus oculi temporalis, external canthus, lateral canthus. (05 Mar 2000) |
| external capsule | A thin lamina of white substance separating the claustrum from the putamen. It joins the internal capsule at either extremity of the putamen, forming a capsule of white matter external to the lenticular nucleus. Synonym: capsula externa, periclaustral lamina. (05 Mar 2000) |
| external cardiac massage | Rhythmic compression of the heart between sternum and spine by depressing the lower sternum backward with the heels of the hands, the patient lying supine. Synonym: external cardiac massage. (05 Mar 2000) |
| external carotid artery | <anatomy, artery> Origin, common carotid at C-4 vertebral level; branches, superior thyroid, lingual, facial, occipital, posterior auricular, ascending pharyngeal, and terminal branches, maxillary and superficial temporal at level of neck of mandible. Synonym: arteria carotis externa. (05 Mar 2000) |