Category:Zona

Zo"na, n.; pl. Zonæ. Etym: [l., a girdle. See zone.]

Defn: a zone or band; a layer. Zona pellucida. Etym: [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 etym: [nl.] (biol.), a radiately striated membrane Situated next the yolk of an ovum, or separated from it by a very Delicate membrane only.