Which spermatid phase (spermiogenesis) is distinguished by the presence of PAS positive granules called pro acrosomal granules?

Correct Answer: A

Rationale: The correct answer is A: Golgi phase. During the Golgi phase of spermiogenesis, the proacrosomal granules are formed from the Golgi apparatus and are PAS positive. These granules will later contribute to the formation of the acrosome in mature sperm. The other choices are incorrect because: B: Cap phase - This phase is characterized by the formation of the acrosomal cap over the nucleus, not the proacrosomal granules. C: Acrosome phase - This phase involves the elongation and shaping of the acrosome, not the formation of proacrosomal granules. D: Maturation phase - This phase focuses on the final maturation and condensation of the sperm cell, not the formation of proacrosomal granules.

Correct Answer: B

Rationale: The correct answer is B: cervix. The cervix is the structure between the uterus and the vagina, serving as the lower part of the uterus that connects to the vagina. It plays a crucial role in pregnancy by allowing sperm to enter the uterus and facilitating the passage of menstrual blood. Rationale: 1. The uterine tube (A) is not the correct answer as it connects the ovaries to the uterus and is not located between the uterus and the vagina. 2. The vulva (C) is the external genitalia and is not the structure between the uterus and the vagina. 3. The hymen (D) is a thin membrane at the opening of the vagina and does not serve as the structure between the uterus and the vagina.

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.