The menstrual cycle

Question 1

Exaplin why GnRH release must be pulsatile. (1)

Answer 1

To reduce the risk of desensitisation.

Question 2

Describe the follicular phase of the ovarian cycle. (8)

Answer 2

Preparing the follicle for ovulation. FSH levels rise and multiple follicles begin development, which prompts cellular proliferation within the follicle causing oestrogen to rise. Negative feedback begins. As the follicle develops, oestrogen rises further, causing positive feedback. Inhibin also rises, inhibiting FSH, so the positive feedback creates the LH surge which prompts ovulation.

Question 3

Describe the luteal phase of the ovarian cycle. (5)

Answer 3

Granulosa and theca cells form the corpus luteum, which secrete progesterone and oestrogen. The progesterone creates negative feedback despite high oestrogen. The corpus luteum has a limited lifespan of 14 days, and regresses if no implantation occurs. Oestrogen, progesterone and inhibin drop.

Question 4

Describe the proliferative phase of the uterine cycle. (2)

Answer 4

Endometrium proliferates and thickens in response to oestrogen. The simple straight glands within the endometrium will coil as they expand.

Question 5

Explain the endometrium. (2)

Answer 5

Endometrial lining divided into the functional layer (sheds during menstruation) and the basal layer (allows for regrowth in the next cycle).

Question 6

Describe the secretory phase of the uterine cycle. (2)

Answer 6

After ovulation, the coiled glands in the endometrium become secretory under the influence of progesterone. In no implantation occurs, the glands lose structure, and the functional layer sheds.

Question 7

Explain what hCG does. (3)

Answer 7

If implantation occurs, the trophoblast (outer cell mass) produces hCG to maintain the corpus luteum until oestrogen and progesterone production is taken over by the placenta.

Question 8

Describe the functions of oestrogen (5).

Answer 8

Increased growth of myometrium 
Increased growth of endometrium 
Secreted watery fluid to conduct sperm
Thins cervical mucus
Peristalsis of Fallopian tubes.

Question 9

Describe the functions of progesterone. (3)

Answer 9

Drastically thickens endometrium
Increased myometrial thickening
Thickening and acidification of cervical mucus.

Question 10

Describe the graph depicting hormone levels. (5)

Answer 10

LH - very high peak on ovulation - the LH surge.
FSH - two little peaks, a slow rise and fall around day 0 and a sharper one around ovulation.
Oestrogen - sharp peak just before ovulation, gradual hump around day 21
Progesterone - large fat peak in the second half.
Inhibin - small bump at ovulation, slightly larger bump around day 21.