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Multiple Choice
Which of the following correctly labels the structures of the implanting blastocyst?
A
Chorion (inner layer), Amnion, Gastrula
B
Epiblast, Hypoblast, Neural tube
C
Trophoblast (outer layer), Inner Cell Mass (embryoblast), Blastocoel (fluid-filled cavity)
D
Zona pellucida (inner layer), Morula, Yolk sac
Verified step by step guidance
1
Step 1: Understand the structure of the blastocyst. The blastocyst is a stage in early embryonic development characterized by a hollow structure containing three main components: the trophoblast (outer layer), the inner cell mass (embryoblast), and the blastocoel (fluid-filled cavity).
Step 2: Differentiate the components of the blastocyst. The trophoblast forms the outer layer and contributes to the formation of the placenta. The inner cell mass (embryoblast) develops into the embryo itself, while the blastocoel is the cavity filled with fluid that provides space for cell movement and growth.
Step 3: Compare the given options. Evaluate each option to determine whether the structures listed correspond to the correct components of the blastocyst. For example, the chorion and amnion are extraembryonic structures that develop later, and the zona pellucida is a glycoprotein layer surrounding the oocyte before fertilization.
Step 4: Eliminate incorrect options. Based on the definitions and timing of development, eliminate options that do not match the structures of the blastocyst. For instance, the neural tube forms during neurulation, which occurs after the blastocyst stage.
Step 5: Confirm the correct answer. The correct labeling of the blastocyst structures is: Trophoblast (outer layer), Inner Cell Mass (embryoblast), Blastocoel (fluid-filled cavity). This matches the description of the blastocyst's components during implantation.