Which of the following portions of the placenta secretes HCG?

Correct Answer: A

Rationale: The correct answer is A: Syncytiotrophoblast. This layer of the placenta secretes human chorionic gonadotropin (HCG), a hormone crucial for maintaining pregnancy by supporting the corpus luteum to produce progesterone. Syncytiotrophoblast is a multinucleated layer formed from the fusion of cytotrophoblast cells and is responsible for hormone secretion. B: Cytotrophoblast is the inner layer of the trophoblast but does not secrete HCG. C: Endometrium is the lining of the uterus and is not part of the placenta. D: Chorion is a membrane that contributes to the formation of the placenta but does not secrete HCG.

Correct Answer: B

Rationale: The correct answer is B: vulva. The vulva includes all external female genital structures, such as the labia, clitoris, and mons pubis. The term "vulva" is the most inclusive and accurate choice, encompassing all components of the external female genitalia. The other options, A, C, and D, refer to specific parts of the vulva, making them incorrect in this context. The labia are the outer and inner folds surrounding the vaginal opening, the clitoris is a highly sensitive organ involved in sexual pleasure, and the mons pubis is the fatty tissue overlying the pubic bone.

Correct Answer: A

Rationale: Progesterone levels rise to their highest point between ovulation and the beginning of menstruation because this is the luteal phase of the menstrual cycle when the corpus luteum (formed from the ruptured follicle after ovulation) secretes progesterone. This hormone prepares the endometrium for implantation and maintains a potential pregnancy. Explanation for other choices: - B: Immediately before ovulation, estrogen levels are high, not progesterone. - C: Luteinizing hormone surge triggers ovulation, not directly related to progesterone rise. - D: The development of primary follicles is associated with estrogen, not progesterone.

Correct Answer: B

Rationale: Correct Answer: B - High levels of progesterone and estrogen during pregnancy suppress milk production. Rationale: 1. Progesterone and estrogen levels are high during pregnancy to maintain the uterine lining and support fetal development. 2. These hormones inhibit the action of prolactin, the hormone responsible for milk production. 3. As a result, the mammary glands are prevented from producing milk until after delivery when progesterone and estrogen levels drop. 4. Once these hormone levels decrease, prolactin can initiate milk production in response to the baby's demand for feeding. Summary of other choices: A: Levels of luteinizing hormone and follicle-stimulating hormone do not directly impact milk production during pregnancy. C: Alveolar cells of the breast may have some developmental changes during pregnancy, but it is not the primary reason for milk production post-delivery. D: Oxytocin is involved in milk ejection, not milk production, and its release is

Correct Answer: B

Rationale: The correct answer is B: Peptide or protein hormones have receptors on the cell membrane. These hormones are typically large molecules that cannot pass through the cell membrane, so they bind to receptors on the cell surface to initiate signal transduction pathways. This allows them to quickly and effectively communicate with target cells. A: They do not have longer half-lives than steroid hormones. Peptide hormones are usually rapidly degraded compared to steroid hormones. C: They do not have a slower onset of action than steroid and thyroid hormones. Peptide hormones can have rapid onset of action due to their signaling pathways. D: They can be stored in endocrine-producing glands, such as insulin being stored in pancreatic beta cells.