| LMCA | left main coronary artery; left middle cerebral artery |
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| MCA | major coronary artery; Maternity Center Association; medical care administration; methylcholanthrene... |
| PA | panic attack; pantothenic acid; paralysis agitans; paranoia; passive aggressive; pathology; patient'... |
| PAD | pain and distress; patient surface axis depth; percutaneous abscess drainage; percutaneous automated... |
| PAH | para-aminohippurate; phenylalanine hydrolase; polycyclic aromatic hydrocarbon; predicted adult heigh... |
| external inguinal ring | The slit-like opening in the aponeurosis of the external oblique muscle of the abdominal wall through which the spermatic cord (round ligament in the female) and inguinal hernias emerge from the inguinal canal. See: aponeurosis of external abdominal oblique muscle. Synonym: annulus inguinalis superficialis, external inguinal ring, subcutaneous ring. (05 Mar 2000) |
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| external intercostal membrane | The membrane that replaces the external intercostal muscle anteriorly between costal cartilages. Synonym: membrana intercostalis externa. (05 Mar 2000) |
| external intercostal muscles | Each arises from lower border of one rib and pass obliquely downward and forward to be inserted into the upper border of rib below; action, contract during inspiration, also maintain tension in the intercostal spaces to resist mediolateral movement; nerve supply, intercostal. Synonym: musculus intercostales externi. (05 Mar 2000) |
| external jugular vein | <anatomy, vein> Superficial vein formed inferior to the parotid gland by the junction of the posterior auricular vein and the retromandibular vein, and passes down the side of the neck crossing to the sternocleidomastoid muscle vertically to empty into the subclavian vein. Synonym: vena jugularis externa. (05 Mar 2000) |
| external lip of iliac crest | The roughened outer margin of the crest that gives attachment to the external oblique and latissimus dorsi muscles above and to the fasciae latae and the tensor fascia lata muscle below. Synonym: labium externum cristae iliacae. (05 Mar 2000) |
| external male genital organs | The external masculine genital organs, the penis and scrotum. Synonym: organa genitalia masculina externa. (05 Mar 2000) |
| 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) |
| 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 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 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) |