What is the smooth, membrane-covered inner fetal side of the placenta called?

The smooth, membrane-covered inner fetal side of the placenta is called the amnion. This structure plays a crucial role in protecting the developing fetus, as it forms a sac that contains amniotic fluid, providing cushioning and helping to maintain a stable temperature. The amnion is derived from the fetal tissue and is essential for fetal development, facilitating movement and allowing for the proper growth of the fetus within the uterus.

The other terms refer to different aspects of the placenta and its associated tissues: chorion refers to the outer fetal membrane and is involved in nutrient exchange, decidua is the maternal tissue that forms the uterine lining after implantation, and villous chorion includes the projections that facilitate nutrient transfer between the mother and fetus. Understanding these distinctions is vital for grasping the anatomy and function of the placenta during pregnancy.