Zone

n. pl. Zonæ .

[L., a girdle. See Zone.]
A zone or band; a layer.

Zona pellucida. [NL.]
(Biol.) (a) The outer transparent layer, or envelope, of the ovum. It is a more or less elastic membrane with radiating striæ, and corresponds to the cell wall of an ordinary cell. See Ovum, and Illust. of Microscope. (b) The zona radiata. -- Zona radiata [NL.]
(Biol.), a radiately striated membrane situated next the yolk of an ovum, or separated from it by a very delicate membrane only.

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Pl. zonae [L.] zone.

• z. alba — the white line in the horse's hoof.
• z. arcuata — see zona glomerulosa (see below).
• z. fasciculata — the thick middle layer of the adrenal gland.
• z. glomerulosa — the outermost layer of the adrenal cortex. Called also zona multiformis.
• z. multiformis — see zona glomerulosa (above).
• z. pellucida — 1. the transparent, noncellular, secreted layer surrounding an ovum.
— 2. area pellucida.
• z. radiata — a zona pellucida exhibiting conspicuous radial striations.
• z. reaction — caused by the penetration of the zona pellucida by the spermatozoa.
• z. reticularis — the innermost layer of the adrenal cortex.
• z. striata — a zona pellucida exhibiting conspicuous striations.

IN BRIEF: n. - (anatomy) any encircling or beltlike structure.

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i zone	Zone Perfect
zone	Polaroid I Zone