| zone of optimal proportion | <chemistry> A zone in a solution of mixed antigen in which the two biomolecules are totally combined. (11 May 1997) |
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| 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) |
| foetal zone | An extensive area of the adrenal gland present in primates during foetal life and for a short period after birth; located between the definitive cortex and the medulla, it contains large steroid-secreting cells arranged in a reticular pattern; involution of this zone in humans is largely completed by three months after birth. Synonym: androgenic zone, foetal reticularis, foetal zone, provisional cortex. (05 Mar 2000) |
| language zone | A large area of the cerebral cortex on the left side (in right-handed persons) considered by some to embrace all the centres of memories and associations connected with language. (05 Mar 2000) |
| latent zone | That portion of the cerebral cortex, the stimulation of which produces no movement and a lesion of which produces no symptoms; mainly the more anterior areas of the frontal lobes. (05 Mar 2000) |
| frontal zone contraction theory | Model proposed to account for the movement of giant amoebae in which cytoplasmic contraction at the front of the leading pseudopod (fountain zone) pulls viscoelastic cytoplasm forward in the centre of the cell and forms a tube of more rigid cytoplasm immediately below the plasma membrane behind the active region. The peripheral contracted cytoplasm relaxes into a weaker gel at the rear and is pulled forward in its turn. Contrasts with the ectoplasmic tube contraction model. (18 Nov 1997) |
| Lissauer's marginal zone | A longitudinal bundle of thin, unmyelinated and poorly myelinated fibres capping the apex of the posterior horn of the spinal gray matter, composed of posterior root fibres and short association fibres that interconnect neighboring segments of the posterior horn. Synonym: fasciculus dorsolateralis, tractus dorsolateralis, dorsolateral tract, fasciculus marginalis, Lissauer's bundle, Lissauer's column, Lissauer's fasciculus, Lissauer's marginal zone, Lissauer's tract, marginal fasciculus, Spitzka's marginal tract, Spitzka's marginal zone, Waldeyer's tract, Waldeyer's zonal layer. (05 Mar 2000) |
| Amberg's lateral sinus line | A line dividing the angle formed by the anterior edge of the mastoid process and the temporal line. (05 Mar 2000) |
| amyotrophic lateral sclerosis | A serious neurologic disease that results from the progressive degeneration of the motor neurons. (27 Sep 1997) |
| amyotropic lateral sclerosis | A chronic progressive disease of motor neurons (the nerves that come from the spinal cord to supply electrical energy to the muscles). (12 Dec 1998) |
| anterior lateral malleolar artery | <anatomy, artery> Origin, anterior tibial; distribution, ankle joint; anastomoses, peroneal, lateral tarsal. Synonym: arteria malleolaris anterior lateralis. (05 Mar 2000) |
| bulb of lateral ventricle | A rounded elevation in the dorsal part of the medial wall of the posterior horn of the lateral ventricle, produced by the major forceps. (05 Mar 2000) |
| bulb of posterior horn of lateral ventricle of brain | Bulb of posterior horn of lateral ventricle of the brain; a curved elevation on the inner wall of the posterior horn produced by the fibres of the forceps major of the corpus callosum as they bend backward into the occipital lobe. Synonym: bulb of posterior horn of lateral ventricle of brain. (05 Mar 2000) |
| vein of lateral recess of fourth ventricle | A small vein originating in the cerebellar tonsil, coursing by the lateral recess of the fourth ventricle on its way to terminate in the petrosal vein. Synonym: vein of lateral recess of fourth ventricle. (05 Mar 2000) |
| ventral lateral nucleus of thalamus | The composite middle third of the ventral nucleus receiving in its various parts distinctive projections from the contralateral half of the cerebellum (by way of the superior cerebellar peduncle) and the ipsilateral globus pallidus; nearly all parts of the nucleus projects to the motor cortex. Synonym: nucleus ventralis intermedius thalami, nucleus ventralis lateralis, ventral lateral nucleus of thalamus. (05 Mar 2000) |