| transitional zone | The equatorial region of the lens of the eye where the anterior epithelial cells become transformed into lens fibres, that portion of a scleral contact lens between the corneal and scleral sections. (05 Mar 2000) |
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| entry zone | The area of the dorsal funiculus of the spinal cord, medial to the tip of the posterior horn, in which the entering fibres of the posterior nerve root divide into ascending and descending branches. (05 Mar 2000) |
| ependymal zone | An inner epithelial layer of cells bordering the lumen of the embryonic neural tube and brain, formed during the latter's stratification, and persisting in modified form throughout life. Synonym: ependymal zone, ventricular layer. (05 Mar 2000) |
| epileptogenic zone | A cortical region which on stimulation reproduces the patient's spontaneous seizure or aura. (05 Mar 2000) |
| equivalence zone | In a precipitin reaction, the zone in which neither antibody nor antigen is in excess. See: precipitation. Synonym: equivalence point. (05 Mar 2000) |
| erogenous zone | An erotogenic zone, areas of the body, such as genitals and nipples, which elicit sexual arousal when stimulated. (05 Mar 2000) |
| trophotropic zone of Hess | An area in the hypothalamus concerned with rewarding bodily sensations. (05 Mar 2000) |
| trummerfeld scurvy zone | <radiology> Lucent band in metaphysis beneath white line of Frankel, seen in scurvy (12 Dec 1998) |
| zone | 1. A girdle; a cincture. "An embroidered zone surrounds her waist." (Dryden) "Loose were her tresses seen, her zone unbound." (Collins) 2. <geography> One of the five great divisions of the earth, with respect to latitude and temperature. The zones are five: the torrid zone, extending from tropic to tropic 46 deg 56 min, or 23 deg 28 min on each side of the equator; two temperate or variable zones, situated between the tropics and the polar circles; and two frigid zones, situated between the polar circles and the poles. "Commerce . . . Defies every wind, outrides every tempest, and invades." (Bancroft) 3. <mathematics> The portion of the surface of a sphere included between two parallel planes; the portion of a surface of revolution included between two planes perpendicular to the axis. 4. A band or stripe extending around a body. A band or area of growth encircling anything; as, a zone of evergreens on a mountain; the zone of animal or vegetable life in the ocean around an island or a continent; the Alpine zone, that part of mountains which is above the limit of tree growth. 5. <chemistry> A series of planes having mutually parallel intersections. 6. Circuit; circumference. Abyssal zone. To girdle; to encircle. <physics> A straight line passing through the center of a crystal, to which all the planes of a given zone are parallel. Origin: F. Zone, L. Zona, Gr.; akin to to gird, Lith. Jsta to gird, Zend yah. Source: Websters Dictionary (01 Mar 1998) |
| zone 1, 2, 3, 4 of West | In pulmonary physiology, defines the levels in a vertical lung according to the relationships of alveolar gas pressure, capillary blood pressure, and pulmonary venous pressure. (05 Mar 2000) |
| zone centrifugation | <technique> High-speed centrifugation inwhich molecules float at a point wheretheir density equals that in a gradient of cesium chloride or sucrose. (12 Jan 1998) |
| zone electrophoresis | <chemistry, procedure> A type of electrophoresis used by physical chemists. In it, the components of a mixture are separated into distinct zones by moving the solution through a porous medium such as filter paper. (06 May 1997) |
| zone of inhibition | <microbiology> The area of no bacterial browth around an antimicrobial agent in the disk-diffusion test. (09 Oct 1997) |
| zone of optimal proportion | <chemistry> A zone in a solution of mixed antigen in which the two biomolecules are totally combined. (11 May 1997) |
| zone of polarizing activity | <cell biology> The small group of mesenchyme cells in avian limb buds that is located at the posterior margin of the developing bud and that produces a substance, possibly retinoic acid, that provides positional information to the developing limb bud. (18 Nov 1997) |