A membrane enveloping the fetus of mammals, external to and enclosing the amnion.
A membrane covering the fertilised ovum.
Outer membrane of the embryo sac, which gives rise to the placenta (the inner membrane is the amnion).
Embryonic membrane that makes up part of the placenta.
The embryonic membrane that totally surrounds the embryo from the time of implantation. It is formed from trophoblast lined with mesoderm and becomes closely associated with the allantois. The blood vessels (supplied by the allantois) are concentrated in the region of the chorion that is attached to the wall of the womb and forms the placenta.
An extraembryonic membrane that, in early development, forms the outer wall of the blastocyst. It is formed from the trophoblast and its lining of mesoderm. From it develop the chorionic villi, which grow into the endometrium and will become the fetal portion of the placenta.
The chorion, which is the outermost embryonic membrane, plays a crucial role in the development of the placenta. It encompasses the amniotic sac or sacs, within which the developing fetuses reside.
The chorion, one of the two membranes enveloping the embryo, is situated on the outer side of the amnion. It features delicate finger-like projections known as chorionic villi and eventually transforms into the placenta.
The outermost membrane of the fetal sac, where the developing baby resides.