Which term describes the membrane surrounding the embryo that forms a fluid-filled cavity?

Which term describes the membrane surrounding the embryo that forms a fluid-filled cavity?

• A. Chorion
• B. Allantois
• C. Germ layer
• D. Amnion

Answer: (D)

The key idea is identifying the extraembryonic membrane that creates a protective fluid-filled space around the developing embryo. The amnion forms the amniotic cavity, which is filled with amniotic fluid. This surrounding fluid cushions the embryo, helps maintain a stable environment, and allows for free movement during growth. The other membranes have different roles: the chorion is the outer membrane involved in exchange and, in mammals, part of the placenta; the allantois handles waste storage and gas exchange; and germ layers are early embryonic tissue layers that give rise to organs and tissues, not a surrounding cavity. So, the membrane that describes a fluid-filled cavity around the embryo is the amnion.

The key idea is identifying the extraembryonic membrane that creates a protective fluid-filled space around the developing embryo. The amnion forms the amniotic cavity, which is filled with amniotic fluid. This surrounding fluid cushions the embryo, helps maintain a stable environment, and allows for free movement during growth. The other membranes have different roles: the chorion is the outer membrane involved in exchange and, in mammals, part of the placenta; the allantois handles waste storage and gas exchange; and germ layers are early embryonic tissue layers that give rise to organs and tissues, not a surrounding cavity. So, the membrane that describes a fluid-filled cavity around the embryo is the amnion.