Frank is a 24 year old man who presents with multiple vesicles and burning erosions on the shaft of his penis and some tender inguinal adenopathy. Which of the following is most likely?

Correct Answer: B

Rationale: The correct answer is B: Herpes simplex. This is because the presentation of multiple vesicles, burning erosions on the penis shaft, and inguinal adenopathy is classic for genital herpes. Primary syphilis (A) presents with a painless chancre, chancroid (C) with painful ulcers, and gonorrhea (D) with urethral discharge or dysuria. Genital herpes is a viral infection caused by HSV-1 or HSV-2 and typically presents with vesicles, erosions, and adenopathy in the affected area.

Correct Answer: B

Rationale: The correct answer is B: Right atrial pressure. Before birth, the fetal circulatory system has a shunt called the foramen ovale that allows blood to bypass the lungs, resulting in higher pressure in the right atrium. After birth, when the foramen ovale closes, the right atrial pressure decreases. Incorrect Choices: A: Arterial Po2 - Typically, arterial Po2 is lower in the fetus due to the placenta's oxygenation, but it increases after birth. C: Aortic pressure - Aortic pressure remains relatively stable before and after birth. D: Left ventricular pressure - Left ventricular pressure increases after birth due to the transition from fetal to neonatal circulation.

Correct Answer: C

Rationale: The correct answer is C: Increased secretion of oxytocin from the paraventricular nuclei. During breast-feeding, oxytocin is released from the paraventricular nuclei in response to suckling. Oxytocin stimulates the contraction of myoepithelial cells around the alveoli and ducts in the breast, facilitating milk ejection. This response helps in the release of milk for the infant's feeding. Rationale: - Choice A is incorrect because ADH is not directly related to breast-feeding. - Choice B is incorrect because ADH is not primarily released from the paraventricular nuclei in response to breast-feeding. - Choice D is incorrect as neurophysin is not directly involved in the hormonal response during breast-feeding.

Correct Answer: D

Rationale: The correct answer is D because two days before menstruation, the corpus luteum secretes estrogen, progesterone, and inhibin, which collectively suppress the hypothalamus's secretion of GnRH and the pituitary gland's secretion of FSH and LH. This hormonal feedback loop helps prepare the body for menstruation. A: The anterior pituitary gland becoming unresponsive to GnRH does not explain the low FSH and LH levels. B: Estrogen from developing follicles typically exerts a positive feedback on the hypothalamus, not inhibitory feedback. C: The rise in body temperature does not directly impact FSH and LH levels; it is more related to ovulation.

Correct Answer: C

Rationale: The correct answer is C: Progesterone from the corpus luteum. After ovulation, the corpus luteum forms from the ruptured follicle and secretes progesterone. Progesterone is responsible for preparing the endometrium for potential implantation of a fertilized egg by increasing its thickness. Luteinizing hormone (A) triggers ovulation but does not directly affect endometrial thickness. Estrogen from the corpus luteum (B) also plays a role in preparing the endometrium but does not specifically stimulate the increase in thickness. Follicle-stimulating hormone (D) primarily regulates the development of ovarian follicles and does not directly influence endometrial thickness.