Correct option is B
Explanation-
Embryonic Stem Cells (ESCs) are pluripotent cells. They are derived from the Inner Cell Mass (ICM) of the blastocyst stage embryo (around day 5–7 after fertilization in mammals). These cells can differentiate into all three germ layers: ectoderm, mesoderm, and endoderm, making them crucial for embryonic development.
Incorrect Options -
Option a: Blastocoel
The blastocoel is just a fluid-filled cavity present inside the blastocyst stage embryo. It plays no role in giving rise to any cells, including embryonic stem cells. ESCs come from a group of cells (the ICM), not from this cavity.
Option c: Trophoectoderm
The trophoectoderm is the outer cell layer of the blastocyst. It gives rise to extra-embryonic structures like the placenta and associated tissues but not to the actual tissues of the embryo. Therefore, ESCs are not derived from trophectoderm.
Option d: Trophoendoderm
The term "Trophoendoderm" is not commonly used in standard mammalian developmental biology texts. It seems to be a misrepresentation or confusion with trophectoderm. Even if it refers to an extra-embryonic layer, such layers contribute to placental or yolk sac tissues, not the embryo. Thus, ESCs do not originate from this layer either.
Correct Option:
Inner Cell Mass (ICM) (Option b)
