Amnion
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The extraembryonic membrane that forms a fluid-filled sac is the amnion. It helps protect and cushion the developing embryo by surrounding it with amniotic fluid.
A vesicle forms as a small sac from the cell's membrane.
Land animals have four extraembryonic membranes: amnion, chorion, allantois, and yolk sac. Aquatic animals typically have fewer extraembryonic membranes as they rely on the water environment for support and protection of their embryos.
Land animals have four extraembryonic membranes: amnion, chorion, allantois, and yolk sac. Aquatic animals typically have fewer extraembryonic membranes, as they do not require as much protection and nutrient transfer during development.
Extraembryonic organs, such as the placenta, yolk sac, and amnion, are called provisional because they play critical roles in supporting the embryo in utero but are ultimately discarded after birth. These organs are temporary structures that facilitate the exchange of nutrients, gases, and waste between the mother and developing embryo until the fetus is born and able to sustain itself.
The chorionic membrane is a thin, outermost membrane that surrounds the fetus in the womb. It is composed of layers of cells derived from both the embryo and the mother and plays a role in the exchange of nutrients and waste between the fetus and the mother. The chorionic membrane eventually fuses with the amniotic membrane to form the amniotic sac.