| peritubular zone | The dentinal matrix surrounding the odontoblastic process; it is more highly calcified and contains finer collagen fibres than does the rest of the dentinal matrix. (05 Mar 2000) |
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| grenz zone | In histopathology, a narrow layer beneath the epidermis that is not infiltrated or involved in the same way as are the lower layers of the dermis. Origin: Ger. Grenze, borderline, boundary (05 Mar 2000) |
| ciliary zone | The outer, wider zone of the anterior surface of the iris, separated from the pupillary zone by the collarette. Synonym: zona ciliaris. (05 Mar 2000) |
| Weil's basal zone | The layer beneath the odontoblasts of the tooth; it contains reticular fibres but few if any cells. Synonym: Weil's basal zone. (05 Mar 2000) |
| Wernicke's zone | The region of the cerebral cortex thought to be essential for understanding and formulating coherent, propositional speech; it encompasses a large region of the parietal and temporal lobes near the lateral sulcus of the left cerebral hemisphere; corresponding approximately to Brodmann's areas 40, 39, and 22. Synonym: sensory speech centre, Wernicke's area, Wernicke's field, Wernicke's region, Wernicke's zone. (05 Mar 2000) |
| comfort zone | The temperature range between 28캜 and 30캜 at which the naked body is able to maintain the heat balance without either shivering or sweating; in the clothed body the range is from 13캜 to 21캜. (05 Mar 2000) |
| motor zone | That portion of the cerebral cortex, primarily the posterior region of the frontal lobe, near the central sulcus, which when stimulated produces a movement and when injured produces spasticity or paralysis. (05 Mar 2000) |
| polar zone | The region in the vicinity of an electrode applied to the body. See: electrotonus. (05 Mar 2000) |
| haemorrhoidal zone | The part of the anal canal that contains the rectal venous plexus. Synonym: annulus haemorrhoidalis, zona haemorrhoidalis. (05 Mar 2000) |
| pregnancy zone proteins | Glycoproteins with the electrophoretic mobility of an alpha 2-globulin. They are found in small amounts in normal human plasma but in much larger volume in the plasma of pregnant women. These proteins have also been found in increased amounts in individuals undergoing oestrogen therapy and are sometimes produced ectopically by tumours of non-placental origin. Pregnancy zone proteins are believed to be of maternal rather than placental origin. (12 Dec 1998) |
| progress zone | An undifferentiated population of mesenchyme cells beneath the apical ectodermal ridge of the chick limb bud from which the sucessive parts of the limb are laid down in a proximo distal sequence. (18 Nov 1997) |
| protective zone | The time in the cardiac cycle, immediately following the vulnerable period, during which a second stimulus will prevent the initiation of ventricular fibrillation by a previous stimulus applied during the vulnerable period, probably by blocking a reentrant pathway. (05 Mar 2000) |
| X zone | A transient adrenocortical zone present in some rodents at birth, most notably in mice, situated between the zona reticularis and the adrenal medulla; it degenerates in males with the secretion at puberty and in females during their first pregnancy; it slowly enlarges in unmated females after puberty and does not degenerate until middle age; the X zone appears to secrete no hormone. Synonym: androgenic zone. Misnomer for the foetal adrenal cortex of primates. Synonym: foetal reticularis. (05 Mar 2000) |
| secondary X zone | An adrenocortical zone, situated in the inner zona fasciculata, that appears upon postpubertal gonadectomy in some male rodents, most notably the mouse; the development of this zone is believed to be stimulated by pituitary gonadotropins. (05 Mar 2000) |
| segmental zone | In a young embryo, the thickened dorsal portion of the undifferentiated paraxial mesoderm which becomes metamerically divided to form the mesodermal somites. Synonym: segmental plate. (05 Mar 2000) |