| Definition: |
The chorioallantoic membrane is a vascular membrane found in eggs of some amniotes, such as birds and reptiles. It is formed by the fusion of the mesodermal layers of two developmental structures: the allantois and the chorion. Three different layers compose the chorioallantoic membrane; these are called the chorionic epithelium, the mesenchyme and the allantoic epithelium. Blood capillaries and sinuses are found between epithelial cells of the chorionic layer, allowing close contact (within 0.2 N
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