The external genitalia of the female are collectively called the

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: 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.

Correct Answer: B

Rationale: The correct answer is B: Ductus venosus. The ductus venosus carries oxygenated blood from the umbilical vein to the inferior vena cava, bypassing the liver. This blood has the highest Po2 among the choices because it is coming directly from the placenta, where oxygen exchange occurs. The other choices (A, C, D) carry deoxygenated blood or blood with lower oxygen content in the fetal circulation. The ductus arteriosus shunts blood from the pulmonary artery to the aorta, so it carries deoxygenated blood. The ascending aorta and left atrium receive mixed oxygenated and deoxygenated blood, not the highest Po2.

Correct Answer: C

Rationale: The correct answer is C: Spermatids are streamlined to form sperm via spermiogenesis. Spermiogenesis is the final stage of spermatogenesis where round spermatids mature into spermatozoa. During spermiogenesis, the spermatids undergo significant structural changes, including the formation of the acrosome, tail, and mitochondria, to become fully functional sperm cells. Choices A and B are incorrect because spermiogenesis does not involve building the stem cell line or producing type A cells. Choice D is incorrect because spermiogenesis does not result in the production of two sperm from one primary spermatocyte; rather, it is the process by which spermatids are transformed into mature sperm cells.