A patient comes in having had repeated colds and infections. Problems in his ear are shown to be due to accumulation of fluid in the middle ear. This is due to a blockage of the:

Correct Answer: D

Rationale: The correct answer is D: Eustachian tube. The Eustachian tube connects the middle ear to the back of the nose and throat, helping to equalize air pressure and drain fluid from the middle ear. Blockage of the Eustachian tube can lead to fluid accumulation in the middle ear, causing ear problems. The other choices, A: Saccule and B: Utricle, are structures in the inner ear related to balance and hearing, not fluid drainage. Choice C: External ear, refers to the outer ear structures and is not involved in middle ear fluid accumulation.

Correct Answer: C

Rationale: Step-by-step rationale for the correct answer (C): 1. After delivery, the baby takes its first breath, increasing oxygen levels. 2. This leads to the closure of the foramen ovale to shift blood flow from the right to the left side. 3. Increased left atrial pressure occurs due to increased blood returning from the lungs. 4. This pressure change causes the foramen ovale to close. Summary of incorrect choices: A: Increased prostaglandin E2 does not directly affect flow through the foramen ovale. B: Increased flow through the pulmonary artery is expected after birth, but it does not directly impact the foramen ovale. D: Increased right atrial pressure would not cause a decrease in flow through the foramen ovale.

Correct Answer: B

Rationale: The correct answer is B: Human chorionic gonadotropin (hCG) stimulates the secretion of testosterone during embryonic development. hCG is produced by the developing embryo and acts on the Leydig cells in the testes to trigger the production of testosterone. This hormone plays a crucial role in male differentiation by promoting the development of male reproductive organs. A: Luteinizing hormone (LH) from the maternal pituitary gland is not involved in the early stages of male differentiation in the embryo. LH is typically involved in the regulation of testosterone production postnatally. C: Inhibin from the corpus luteum is not involved in the stimulation of testosterone secretion during embryonic development. Inhibin is mainly involved in the negative feedback regulation of FSH secretion. D: Gonadotropin-releasing hormone (GnRH) from the embryo's hypothalamus is not responsible for directly stimulating testosterone secretion during embryonic development. GnRH regulates the secretion

Correct Answer: C

Rationale: The correct answer is C because the resistance of the arterioles supplying the corpora cavernosa increases. This occurs due to the contraction of smooth muscle in the arterioles stimulated by sympathetic nervous system activity post-ejaculation. This constriction of arterioles reduces blood flow into the corpora cavernosa, leading to the flaccid state. Choice A is incorrect because systemic arterial pressure does not decrease significantly post-ejaculation. Choice B is incorrect as decreased sympathetic stimulation would actually lead to vasodilation, not vasoconstriction. Choice D is incorrect because the release of nitric oxide by the parasympathetic nervous system would lead to vasodilation, not vasoconstriction.

Correct Answer: D

Rationale: The correct answer is D: Ejaculation. Motor neurons control muscle movements, including those involved in ejaculation. Since the motor neurons below the thoracic region are damaged, the man would not be able to ejaculate. Arousal (A), erection (B), and lubrication (C) are controlled by different mechanisms and do not solely rely on motor neurons in the spinal cord.