In mammals, the __________ facilitates implantation in the uterine wall.

• A. blastocyst
• B. hypoblast
• C. amnion
• D. epiblast
• E. trophoblast

Answer: (E)

Verified step by step guidance

1. Understand the context: The question is about the process of implantation in mammals, which is a crucial step in early pregnancy where the embryo attaches to the uterine wall.
2. Identify the key term: The term 'trophoblast' is mentioned as the correct answer. It is important to know what the trophoblast is and its role in implantation.
3. Define the trophoblast: The trophoblast is the outer layer of cells in the blastocyst, which is an early stage in the development of the embryo. It plays a critical role in implantation by interacting with the uterine wall.
4. Explain the function: The trophoblast facilitates implantation by secreting enzymes that allow the blastocyst to penetrate the uterine lining, establishing a connection with the maternal blood supply.
5. Differentiate from other terms: Understand why the other options (blastocyst, hypoblast, amnion, epiblast) are not correct. The blastocyst is the structure containing the trophoblast, the hypoblast and epiblast are layers within the embryo, and the amnion is a membrane that forms later in development.