Two sacs of tissue, the inner amnion and the outer amnion, that encloses the developing fetus in the uterus.
Collectively, the amnion, chorion, and umbilical cord (which includes the yolk stalk, allantois, and blood vessels), all of which function for the protection, nourishment, respiration, and excretion of the developing fetus. The placenta, of both fetal and maternal tissue, also serves these functions.
One of the membranous structures that protect and support the embryo and provide its nutrition, respiration, and excretion. The structures are yolk sac, allantois, amnion, chorion, decidua, and placenta.