| 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) |
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| 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) |
| zona perforata | The perforations along the tympanic lip of the spiral lamina giving passage to the cochlear nerves. Synonym: habenulae perforata, zona perforata. (05 Mar 2000) |
| zona pupillaris | The central region of the anterior surface of the iris located between the collarette and the pupillary margin. Synonym: zona pupillaris. (05 Mar 2000) |
| zona radiata | The thickened cell membrane of the ovum in forms, such as certain amphibia, in which it appears radially striated under the light microscope; with the electron microscope the striations can be seen to be microvilli. Synonym: membrana striata, striated membrane, zona radiata. (05 Mar 2000) |
| zona reticularis | The inner zone of the adrenal cortex. This zone consists of an anastomosing network of cells which resemble those of the zona fasciculata except for the fact that they contain less lipid. The mitochondria are elongated and contain a mixture of tubular and flattened cristae. (12 Dec 1998) |
| zona serpiginosa | <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 striata | The thickened cell membrane of the ovum in forms, such as certain amphibia, in which it appears radially striated under the light microscope; with the electron microscope the striations can be seen to be microvilli. Synonym: membrana striata, striated membrane, zona radiata. (05 Mar 2000) |
| zona tecta | The inner third of the basilar membrane of the cochlear duct extending from the tympanic lip of the osseous spiral lamina to the outer pillar cell of the spiral organ (of Corti). Synonym: zona arcuata, zona tecta. (05 Mar 2000) |
| zona vasculosa | An area in the external acoustic meatus where a number of minute blood vessels enter from the mastoid bone. Synonym: spongy spot, zona vasculosa. (05 Mar 2000) |
| apertura externa aqueductus vestibuli | The external opening of the vestibular aqueduct on the posterior surface of the petrous part of the temporal bone near the groove for the sigmoid sinus. Synonym: apertura externa aqueductus vestibuli. (05 Mar 2000) |
| apertura externa canaliculi cochleae | The external opening of the cochlear aqueduct on the temporal bone medial to the jugular fossa. Synonym: apertura externa canaliculi cochleae. (05 Mar 2000) |
| arteria carotis externa | <anatomy, artery> Origin, common carotid at C-4 vertebral level; branches, superior thyroid, lingual, facial, occipital, posterior auricular, ascending pharyngeal, and terminal branches, maxillary and superficial temporal at level of neck of mandible. Synonym: arteria carotis externa. (05 Mar 2000) |
| arteria iliaca externa | <anatomy, artery> Origin, common iliac; branches, inferior epigastric, deep circumflex iliac; becomes the femoral at the inguinal ligament. Synonym: arteria iliaca externa. (05 Mar 2000) |