Outer cell mass gives rise to?
**Core Concept**
The outer cell mass, also known as the trophectoderm, plays a crucial role in the early development of the embryo. It is one of the two distinct cell layers that form during the blastocyst stage, the other being the inner cell mass.
**Why the Correct Answer is Right**
The outer cell mass gives rise to the trophoblast, which is responsible for the formation of the placenta and other supporting tissues. This process is initiated by the invasion of trophoblast cells into the endometrium, where they differentiate into cytotrophoblast and syncytiotrophoblast. The cytotrophoblast gives rise to the Langhans cells, which are involved in implantation, while the syncytiotrophoblast produces human chorionic gonadotropin (hCG) and human placental lactogen (hPL). The trophoblast also contributes to the formation of the chorionic villi, which are essential for gas and nutrient exchange between the fetus and the mother.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the origin of any embryonic structures.
* **Option B:** This option is incorrect because the inner cell mass gives rise to the embryoblast, not the outer cell mass.
* **Option C:** This option is incorrect because while the outer cell mass does contribute to the formation of the placenta, it is not the primary tissue responsible for the development of the fetal membranes.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that the outer cell mass (trophectoderm) and the inner cell mass (embryoblast) are distinct cell layers that give rise to different embryonic structures. This knowledge is crucial for understanding the normal development of the embryo and the pathophysiology of various pregnancy-related complications.
**Correct Answer:** C.