vitelline membrane

views updated Jun 11 2018

vitelline membrane The membrane that surrounds the ovum of animals, from which it has been secreted (e.g. in birds this is the membrane surrounding the yolk of the egg). In Drosophila the term is used rather specifically for the membrane that immediately surrounds the plasma membrane of the ovum. In this case it is formed by the fusion of deposits in the intercellular space between the oocyte and columnar follicle cells that surround it.

zona pellucida

views updated May 23 2018

zona pellucida A layer of glycoprotein that surrounds the plasma membrane of a mammalian egg cell. It develops as a jelly coat around the primary oocyte and is surrounded by the granulosa cells.

zona pellucida

views updated May 17 2018

zona pellucida (zoh-nă pel-oo-sid-a) n. the thick membrane that develops around the mammalian oocyte within the ovarian follicle. See ovum.

zona pellucida

views updated May 14 2018

zona pellucida The transparent covering of an oocyte.

vitelline membrane

views updated May 11 2018

vitelline membrane See egg membrane.