| aplanatism | Freedom from spherical aberration; said of a lens. Origin: G. A-priv. + planetos, wandering (05 Mar 2000) |
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| aplasia | <embryology> A lack of development of an organ or tissue or of the cellular products from an organ or tissue. Compare: hypoplasia. Origin: Gr. Plassein = to form (18 Nov 1997) |
| aplasia cutis congenita | Congenital absence or deficiency of a localised area of skin, with the base of the defect covered by a thin translucent membrane; most often a single area near the vertex of the scalp, but may occur in other areas; underlying structures may also be affected; autosomal inheritance, either dominant or recessive. (05 Mar 2000) |
| aplastic | <pathology> Lacking in cell production, as in aplastic anaemia. Origin: Gr. Plassein = to form (27 Sep 1997) |
| aplastic anaemia | <haematology> This form of anaemia occurs when the bone marrow ceases sufficient red and white blood cell production. It may be induced by exposures to high levels of toxic chemicals, radiation and certain drugs. It is generally unresponsive to specific therapy, often accompanied by granulocytopenia and thrombocytopenia, in which the bone marrow may not necessarily be hypocellular or hypoplastic but fails to produce adequate numbers of peripheral blood elements. The term actually is all inclusive and most probably encompasses several clinical syndromes. Origin: Gr. Haima = blood (29 Sep 1997) |
| aplastic lymph | Lymph containing a relatively large number of leukocytes, but comparatively little fibrinogen; such lymph does not form a good clot and manifests only a slight tendency to become organised. Synonym: corpuscular lymph. (05 Mar 2000) |
| apleuria | Congenital absence of one or more ribs; usually associated with absent transverse process or processes. Origin: a-priv. + G. Pleura, rib (05 Mar 2000) |
| aplotomy | <surgery> Simple incision. Origin: Gr. Simple + a cutting. Source: Websters Dictionary (01 Mar 1998) |
| aplustre | An ornamental appendage of wood at the ship's stern, usually spreading like a fan and curved like a bird's feather. Origin: L, fr. Gr. Source: Websters Dictionary (01 Mar 1998) |
| Aplysia | <marine biology> Opisthobranch mollusc with reduced shell, favourite source of ganglia for neurophysiological study. (18 Nov 1997) |
| apna | <medicine> Partial privation or suspension of breath; suffocation. Origin: NL, fr. Gr. Priv. +, breath, to breathe, blow. Source: Websters Dictionary (01 Mar 1998) |
| apnea | <clinical sign> Cessation of breathing. (18 Nov 1997) |
| apneic | Related to or suffering from apnea. (05 Mar 2000) |
| apneic oxygenation | Maintenance of oxygenation during apnea by intratracheal insufflation of oxygen at high flow rates. Synonym: apneic oxygenation. (05 Mar 2000) |
| apneic pause | Cessation of air flow for more than 10 seconds. See: sleep apnea. (05 Mar 2000) |