Question

During the development of a mammalian embryo, "yolk sac" is formed by which one of the following?

• A. {Syncytiotrophoblast}
• B. {Primitive endoderm (hypoblast)}
• C. {Amniotic ectoderm}
• D. {Embryonic epiblast}

Hint:

The yolk sac is formed from the primitive endoderm (hypoblast) and plays an important role in early nutrition and blood circulation before the placenta is functional.

Answer 1

The Correct Option is B

The yolk sac in mammals is an early embryonic structure that plays a key role in providing nutrients to the developing embryo before the placenta is fully functional. It is formed from the primitive endoderm or hypoblast, a layer of cells that arises during the early stages of development. The yolk sac is an important structure during early development, as it is responsible for providing the nutrients and oxygen necessary for the growth of the embryo.
The primitive endoderm (hypoblast) forms part of the inner layer of the embryo and gives rise to the yolk sac, which is crucial for early nutrition and blood circulation. As the embryo develops further, other structures such as the placenta take over these functions.
The syncytiotrophoblast (option A) is involved in the formation of the placenta, but it does not contribute to the formation of the yolk sac. The amniotic ectoderm (option C) forms the amniotic sac, and the embryonic epiblast (option D) gives rise to the embryo itself, but neither of these directly forms the yolk sac.