Resumen de The placenta. (Cover story)
The article discusses the evolution of the placenta and how it evolved from an eggshell membrane known as the chorion into an organ that allows a fetus to grow in a womb. Topics include an overview of the progenitors of modern mammals, which are animals that give birth to live young, the physiological processes that make live birth possible, such as the formation of placenta, which envelopes the embryo and supplies nutrients, and how the placenta prevents the mother from rejecting the fetus.
