| zona ciliaris | 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) |
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| zona corona | An irregularly disposed collection of visible veins seen in the skin of people usually of or past middle age; it has no specific connection with any deep structure, such as the diaphragm, and no necessary connection with underlying visceral disease. Synonym: zona corona. (05 Mar 2000) |
| zona dermatica | A ridge of thickened skin surrounding the protrusion in spina bifida. (05 Mar 2000) |
| zona epithelioserosa | The membranous ring, within the zona dermatica, surrounding the protrusion in spina bifida. (05 Mar 2000) |
| zona facialis | Herpes zoster involving the face. (05 Mar 2000) |
| zona fasciculata | The wide middle zone of the adrenal cortex. This zone consists of large lipid-laden cells radially arranged in parallel cords. It converts pregnenolone to cortisol by a series of enzymatically regulated steps. A small amount of corticosterone is formed as a by-product of cortisol synthesis. (12 Dec 1998) |
| zona glomerulosa | The narrow subcapsular outer zone of the adrenal cortex. This zone consists of granular cells which stain deeply and are arranged in rounded groups. It converts pregnenolone to aldosterone by a series of enzymatically regulated steps. (12 Dec 1998) |
| zona haemorrhoidalis | The part of the anal canal that contains the rectal venous plexus. Synonym: annulus haemorrhoidalis, zona haemorrhoidalis. (05 Mar 2000) |
| zona ignea | <virology> A reactivation of the same Herpes virus that is responsible for chicken pox. This results in a painful blistery red rash that is confined to one side of the body. The zoster rash affects one nerve distribution or dermatome. Facial rash can lead to optic nerve involvement with resultant blindness. Synonym: shingles. (06 Mar 1998) |
| zona incerta | A flat, obliquely disposed plate of gray matter in the subthalamic region situated between the thalamic fasciculus (tegmental field H1 of Forel) and the lenticular fasciculus (tegmental field H2). Medially, cells of this nucleus are adjacent to the prerubral area (tegmental field H) and, laterally, they are continuous with the reticular nucleus of the thalamus. Z. I. Is a derivative of the ventral thalamus; it receives afferents from the precentral motor cortex and the cerebellum. (05 Mar 2000) |
| zona medullovasculosa | The fissured segment of the spinal cord that dorsally closes the sac in meningomyelocele. (05 Mar 2000) |
| zona ophthalmica | Herpes zoster in the distribution of the ophthalmic nerve. (05 Mar 2000) |
| zona orbicularis | Fibres of the articular capsule of the hip joint encircling the neck of the femur. Synonym: orbicular zone, ring ligament, zonular band. (05 Mar 2000) |
| zona pectinata | The outer two-thirds of the basilar membrane of the cochlear duct. Synonym: zona pectinata. (05 Mar 2000) |
| zona pellucida | <cell biology, gynaecology> A translucent, elastic, noncellular layer surrounding the ovum of many mammals. (11 May 1997) |