vitelline membrane
Quick Summary
The vitelline membrane is a biological layer that encloses an egg. In mammals, this membrane is known as the zona pellucida. In many invertebrates and amphibians, as well as some fish, the vitelline membrane separates from the egg's surface after fertilization, forming a fertilization membrane.1
In zoology, the egg is the female sex cell, or gamete. While the ovum is the single cell, the term "egg" can refer to the ovum along with its protective membranes and nutritive materials. The vitelline membrane is the innermost membrane surrounding the egg in most animal species, except for some cnidarians.2
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.
egg…of which is called the vitelline membrane. The vitelline membrane is the only membrane in the eggs of various invertebrates—ctenophores, many worms, and echinoderms—and of certain lower chordates. All higher vertebrates and many invertebrates have one or more additional membranes. Insect eggs, for example, are covered by a thick, hard…
Read More…of which is called the vitelline membrane. The vitelline membrane is the only membrane in the eggs of various invertebrates—ctenophores, many worms, and echinoderms—and of certain lower chordates. All higher vertebrates and many invertebrates have one or more additional membranes. Insect eggs, for example, are covered by a thick, hard…
Read More
animal developmentPreparatory eventsIn frogs, a very thin vitelline membrane forms around the eggs in the ovary; subsequently a layer of jelly is deposited around the eggs while they pass through the oviducts. In birds, a very thin vitelline membrane is produced around the egg in the ovary; then several layers of secondary…
Read MoreIn frogs, a very thin vitelline membrane forms around the eggs in the ovary; subsequently a layer of jelly is deposited around the eggs while they pass through the oviducts. In birds, a very thin vitelline membrane is produced around the egg in the ovary; then several layers of secondary…
Read More