| IR | drop of voltage across a resistor produced by a current; ileal resection; immune response; immunizat... |
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| IRV | inferior radicular vein; inspiratory reserve volume; inverse ratio ventilation |
| ITA | inferior temporal artery; internal thoracic artery; International Tuberculosis Association |
| ITQ | inferior temporal quadrant |
| ITV | inferior temporal vein |
| external malleolar sign | <clinical sign> When the external malleolar skin area is irritated, extension of the great toe occurs in cases of organic disease of the corticospinal reflex paths. Synonym: Chaddock reflex, external malleolar sign. (05 Mar 2000) |
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| external malleolus | The process at the lateral side of the lower end of the fibula, forming the projection of the lateral part of the ankle; the lateral malleolus is more inferiorly placed then the medial malleolus. Synonym: malleolus lateralis, external malleolus, extramalleolus, outer malleolus. (05 Mar 2000) |
| external mammary artery | <anatomy, artery> Origin, axillary; distribution, muscles of chest and mammary gland. Synonym: arteria thoracica lateralis, external mammary artery, long thoracic artery. (05 Mar 2000) |
| external matrix | The substance occupying the space between the inner and outer membrane of any organelle (e.g., mitochondria) with a double membrane. (05 Mar 2000) |
| external maxillary artery | <anatomy, artery> Origin, external carotid; branches, ascending palatine, tonsillar and glandular branches, submental, inferior labial, superior labial, masseteric, buccal, lateral nasal branches, and angular. Synonym: arteria facialis, arteria maxillaris externa, external maxillary artery. (05 Mar 2000) |
| 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) |
| 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) |