Extraembryonic Membranes

**Definition:** The thin layers of tissue that surround the developing embryo. There are four extra-embryonic membranes commonly found in VERTEBRATES, such as REPTILES; BIRDS; and MAMMALS. They are the YOLK SAC, the ALLANTOIS, the AMNION, and the CHORION. These membranes provide protection and means to transport nutrients and wastes.

**Tree numbers:** - A10.615.284 - A16.254.750

**Synonyms:** - Extra-Embryonic Membranes