Week 3: Follicular Phase

Question 1

Describe estrogen levels in the folliclular phase of the ovarian cycle

Answer 1

Granulosa cells around the primary follicle continue to proliferate throughout the follicular phase as well as get a boost from the Theca cells around the follicle in the form of androstenedione which is converted to estrogen by the granulosa cells so the estrogen level continues to rise throughout the follicular phase

Question 2

Decribe the uterine cycle in the folliclular phase

Answer 2

From around day 1 the endometrium continues shedding (Menses phase) until estrogen levels from the growing follicle get high enough to cause the endometrium to proliferate and prepare for egg implantation (Proliferative phase)

Question 3

Describe the levels of gonadotropic hormones during the follicular phase

Answer 3

As the hypothalamus begins to sense that the estrogen levels in the body are really high due to the production of mature follicle(s) they begin to release less FSH and LH. so get a dip of LH and FSH in the blood

(which makes sense because the reason FSH and LH were released in the first place was to signal the follicles to start developing)

But then, the granulosa cells produce even more estrogen and also progesterone and inhibin which inhibit the release of FSH and LH

However, when a threshold of estrogen levels in the blood is reached it paradoxically causes a massive release of LH and a large increase of FSH

The difference in LH to FSH is due to the presence of Inhibin which inhibits release of FSH but doesn’t really effect LH, causing an event called the luteal surge.

The luteal surge pushes the follicle to reach its final steps of development (Ovulation) where the egg pops out of the follicle (day 14)

Question 4

Reproductive cycle graph

Answer 4