(Greek: skin, membrane, leather; protective fetal membrane)
The chorioallantoic membrane is highly vascularized and is used experimentally as a site upon which to place pieces of tissue in order to test their invasive capacity.
2. A membrane surrounding an embryo.
In a bird's or reptile's egg, it lies next to the shell. In mammals, it forms a major part of the placenta.
2. The outermost of the two fetal membranes, the amnion being the innermost, which together surround the embryo.
The chorion develops villi (vascular fingers) and gives rise to the placenta.
In Greek, the word chorion means, "skin" or "leather".