Question 1

Which hormone is primarily responsible for triggering ovulation in eutherian females, and what is the mechanism by which it is released?

Accepted Answer

Luteinizing hormone (LH); released in a surge following a critical increase in estradiol activating the hypothalamic surge center

Question 2

In the male reproductive system, which cell type does FSH act upon to indirectly stimulate spermatogenesis, and what is the immediate effect?

Accepted Answer

Sertoli cells; increased mitosis and release of paracrine factors

Question 3

Which feedback mechanism is unique to the female hypothalamic-pituitary-gonadal axis during the midcycle phase?

Accepted Answer

Positive feedback of estrogen on the surge center, leading to an LH surge

Question 4

What is the primary function of inhibin secreted by Sertoli cells in males?

Accepted Answer

Selectively inhibit FSH release from the adenohypophysis

Question 5

During the luteal phase, which hormones inhibit further follicular development and prevent a second ovulatory episode?

Accepted Answer

Estrogen and progesterone

Question 6

Aromatase knockout male mice exhibit disrupted spermatogenesis. What does this observation suggest about the role of estrogens in the testis?

Accepted Answer

Estrogens, produced locally via aromatase, facilitate spermatogenesis through estrogen receptors on germ cells

Question 7

Which of the following best describes the two-cell, two-gonadotropin model of estrogen synthesis in the ovarian follicle?

Accepted Answer

LH stimulates thecal cells to produce androgens, which are aromatized to estrogen by FSH-stimulated granulosa cells

Question 8

Which signaling pathway is activated by LH binding to its receptor on granulosa cells during ovulation, and what is one of its key downstream effects?

Accepted Answer

MAPK/ERK pathway; increases transcription of genes involved in follicle rupture and luteinization

Question 9

What is the role of oxytocin and prostaglandin F2α (PGF2α) in the process of luteolysis?

Accepted Answer

Oxytocin from the pars nervosa triggers pulses of PGF2α, which induces luteolysis

Question 10

A patient presents with abnormally low levels of FSH but normal LH. Which feedback regulator is most likely overactive?

Accepted Answer

Inhibin

Question 11

Which of the following best explains why testosterone concentrations are much higher within the testis compared to circulating levels?

Accepted Answer

High intratesticular testosterone is required for paracrine regulation of spermatogenesis

Question 12

Which event marks the transition from the follicular phase to the luteal phase in the ovarian cycle?

Accepted Answer

Ovulation

Question 13

What is the effect of activin on granulosa cells during the follicular phase?

Accepted Answer

Increases P450aro activity, enhancing estrogen synthesis

Question 14

Which of the following best describes the role of the corpus luteum in the menstrual cycle?

Accepted Answer

It secretes estrogens and progesterone to inhibit further ovulation

Question 15

A researcher blocks the action of interferon tau (IFNT) in a pregnant mammal. What is the most likely outcome?

Accepted Answer

Luteolysis occurs due to unblocked PGF2α pathway, leading to loss of the corpus luteum

Question 16

Which of the following is a direct effect of ERK1/2 activation in granulosa cells during ovulation?

Accepted Answer

Increased transcription of genes for cumulus-oocyte complex (COC) formation and follicle rupture

Question 17

Which cell type is responsible for androgen synthesis in the testis, and which hormone stimulates this process?

Accepted Answer

Leydig cell; LH

Question 18

Which of the following best describes the feedback effect of progesterone on the hypothalamic-pituitary axis during the luteal phase?

Accepted Answer

Negative feedback on both tonic and surge centers, inhibiting GnRH release

Question 19

Which process is directly inhibited by inhibin in both males and females?

Accepted Answer

FSH secretion

Question 20

A patient has a mutation that prevents the formation of tight junctions between Sertoli cells. Which of the following is the most likely consequence?

Accepted Answer

Disruption of the blood-testis barrier, leading to impaired spermatogenesis

The Reproductive System: Hormonal Regulation and Gametogenesis in Mammals

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