Correct option is B
The inner cell mass (ICM) of the blastocyst does not differentiate into trophectoderm. Instead, it gives rise to the embryonic germ layers: ectoderm, mesoderm, and endoderm. The trophectoderm, which forms the placenta and extraembryonic tissues, originates from cells external to the ICM. The ICM is pluripotent and is responsible for forming the embryo proper.
Information Booster:
- Totipotent cells can form all embryonic and extraembryonic structures (e.g., 4-cell stage).
- Pluripotent cells of the ICM form the three germ layers but not extraembryonic tissues.
- Unipotent cells can differentiate into one cell type (e.g., spermatogonial stem cells).
- Multipotent cells can generate multiple related cell types (e.g., hematopoietic stem cells).
- The trophectoderm forms the outer layer of the blastocyst and contributes to the placenta.
Additional Knowledge:
- 4-cell stage mouse embryo (Option a):
These cells are totipotent, meaning they have the potential to form all embryonic and extraembryonic structures, including the placenta. - Inner cell mass (Option b):
Incorrect. The ICM gives rise to the embryo proper and differentiates into the three germ layers (ectoderm, mesoderm, endoderm). The trophectoderm, which contributes to the placenta, originates from outer blastocyst cells, not the ICM. - Spermatogonial stem cells (Option c):
These are unipotent cells in the testis, capable of differentiating only into sperm cells. - Hematopoietic stem cells (Option d):
These are multipotent, meaning they can differentiate into various blood cell types, including red blood cells, white blood cells, and platelets.
