| external maxillary plexus | An autonomic plexus on the facial artery derived from the external carotid plexus; it sends a branch to the submandibular ganglion. Synonym: external maxillary plexus, plexus maxillaris externus. (05 Mar 2000) |
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| external medium | The medium or fluid in which a disperse is suspended. Synonym: continuous phase, dispersion medium, dispersion phase, external medium. (05 Mar 2000) |
| external meningitis | Inflammation of the outer surface of the dura mater. Synonym: epidural meningitis, external meningitis. (05 Mar 2000) |
| external naris | 1. <anatomy> One of the external openings of the nose, which give passage to the air breathed and to secretions from the nose and eyes; one of the anterior nares. In sperm whales, porpoises, and allied animals, there is only one nostril, which is situated on the top of the head and called a spiracle. 2. Perception; insight; acuteness. "Methinks a man Of your sagacity and clear nostril should Have made another choice." (B. Jonson) Origin: OE. Nosethril, nosethirl, AS. Nospyrl; nos for nosu nose + pyrel opening, hole, from pyrel pierced, for pyrhel, fr. Purh through. See Nose, and Through, and cf. Thrill. Source: Websters Dictionary (01 Mar 1998) |
| external nasal branches | Branches to external aspect of nose. The external nasal branches of 1) infraorbital nerve, rami nasales externii nervi infraorbitalis, 2) nasociliary nerve, rami nasales externi nervi ethmoidalis anterioris. Synonym: rami nasales externi. (05 Mar 2000) |
| external nasal veins | Several vessels that drain the external nose, emptying into the angular or facial vein. Synonym: venae nasales externae. (05 Mar 2000) |
| external nose | The visible portion of the nose which forms a prominent feature of the face; it consists of a root, dorsum and apex from above downward and is perforated inferiorly by two nostrils separated by a septum. Synonym: nasus externus, nasus. (05 Mar 2000) |
| external nuclear layer of retina | The outermost layer of the cerebral layer of retina, composed of the primary receptor cells of the retina; the stratum consists of two sublayers: 1) an external layer made up of the rods and cones, the photosensitive processes of the receptor cells, and 2) the external nuclear layer containing the cell bodies of these cells; the external limiting membrane forms a perforated supporting plate between the two sublayers; the name refers to the fact that the retinal receptor cells are a specialised form of (epithelial) ependyma cell and thus, in a sense, are comparable to the neuroepithelial cells (e.g., hair cells) of other sense organs. Synonym: external nuclear layer of retina, stratum neuroepitheliale retinae, stratum nucleare externum retinae. (05 Mar 2000) |
| external oblique | <anatomy, muscle> Origin, fifth to twelfth ribs; insertion, anterior half of lateral lip of iliac crest, inguinal ligament, and anterior layer of the rectus sheath; action, diminishes capacity of abdomen, draws thorax downward; nerve supply, thoracoabdominal nerves. Synonym: musculus obliquus externus abdominis, abdominal external oblique muscle. (05 Mar 2000) |
| external oblique reflex | Contraction of the external oblique and rectus abdominis muscles upon tapping the anterior and outer part of the lower thoracic wall. (05 Mar 2000) |
| external oblique ridge | A horizontal bony crest on the external surface of the body of the mandible, inferior to the alveolar bone, marking the site of attachment of the buccinator muscle. (05 Mar 2000) |
| external obturator muscle | <anatomy, muscle> Origin, lower half of margin of obturator foramen and adjacent part of external surface of obturator membrane; insertion, trochanteric fossa of greater trochanter; action, rotates thigh laterally; nerve supply, obturator. Synonym: musculus obturator externus, external obturator muscle. (05 Mar 2000) |
| external occipital crest | A ridge extending from the external occipital protuberance to the border of the foramen magnum. Synonym: crista occipitalis externa, linea nuchae mediana. (05 Mar 2000) |
| external occipital protuberance | A prominence about the centre of the outer surface of the squamous portion of the occipital bone, giving attachment to the ligamentum nuchae. Synonym: protuberantia occipitalis externa. (05 Mar 2000) |
| external opening of urethra | 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) |