Here's a breakdown:
* Amnion: A thin, tough membrane that encloses the embryo in a fluid-filled sac called the amniotic sac. This sac protects the embryo from physical damage and helps regulate temperature.
* Amniotic Sac: The fluid-filled sac within the amnion that cushions the embryo, allows movement, and prevents dehydration.
While the amnion is the primary protective structure, other structures also contribute to the embryo's safety:
* Chorion: The outermost membrane that surrounds the embryo and the amnion. It's involved in gas exchange and nutrient transfer.
* Yolk Sac: Provides nourishment to the embryo in the early stages of development.
* Allantois: A sac that stores waste products from the embryo.
Together, these structures form the amniotic egg, which is a crucial adaptation that allowed vertebrates to move onto land.
