What is the primary purpose of the amnion in embryonic development?

The primary purpose of the amnion in embryonic development is to cushion the embryo. The amnion is a membrane that surrounds the embryo and is filled with amniotic fluid, which serves to protect the developing fetus from physical shocks and helps to maintain a stable temperature. This cushioning effect is crucial, especially during the various movements that occur within the uterus, as it prevents injury to the embryo from potential impacts against the surrounding tissues or from movements of the mother.

While the other choices relate to important aspects of embryonic development, they do not directly pertain to the specific role of the amnion. Nutrient supply primarily comes from the placenta, gas exchange occurs through the placenta as well, and cell differentiation is guided by various factors in the embryo's environment rather than specifically by the amnion itself. Thus, the cushioning function is central to the amnion's role in protecting the embryo during development.