The trophoblast eventually differentiates into two layers. Which of these layers erodes the endometrium and begins projecting extensions into the uterine lining?

• A. The cytotrophoblast.
• B. The syncytiotrophoblast.
• C. The blastocyst.
• D. The morula.

Answer: (B)

Verified step by step guidance

1. Begin by understanding the structure of the blastocyst, which is an early stage in embryonic development. The blastocyst consists of an inner cell mass and an outer layer called the trophoblast.
2. The trophoblast is crucial for implantation into the uterine lining. It differentiates into two distinct layers: the cytotrophoblast and the syncytiotrophoblast.
3. The cytotrophoblast is the inner layer of the trophoblast, consisting of individual cells that retain their cell membranes.
4. The syncytiotrophoblast is the outer layer of the trophoblast. It is characterized by a multinucleated cell mass that lacks distinct cell boundaries.
5. The syncytiotrophoblast is responsible for eroding the endometrium and projecting extensions into the uterine lining, facilitating implantation and establishing the placenta.