CH 8 (part 1) The follicular phase of the estrous cycle

Question 1

When does the follicular phase occur? What does it consist of?

Answer 1

Initiated after luteolysis

Consists of proestrus and estrus

Question 2

What happens to follicular phase during and after luteal phase?

Answer 2

During luteal phase - high progesterone

At luteolysis - the negative feedback of progesterone on the hypothalamus is removed. This causes GnRH to be released at higher amplitudes and frequencies that during luteal phase.

Question 3

What 4 events take place during follicular phase?

Answer 3

• gonadotropin release from anterior pituitary
• follicular preparation for ovulation
• sexual receptivity
• ovulation

Question 4

What is the follicular phase governed by?

Answer 4

hypothalamus, anterior pituitary, and ovary

Question 5

What does the surge center control?

Answer 5

Surge center responds dramatically to high estrodiol -
positive feedback of estradiol on neurons of the surge center

Question 6

What does the tonic center do?

Answer 6

Basa secretion of GnRH

Question 7

What happens when there is high estrogen concentration?

Answer 7

When estrogen concentration in blood reaches a certain level, a large quantity of GnRH is released from neurons located in surge center.

Question 8

What happens during the follicular phase?

Answer 8

Follicles produce more estradiol as the amount of follicular fluid increases in these follicles. Once this estradiol reaches a certain threshold level, it triggers the surge center to release spike of GnRH which leads to the spike of LH and FSH from the anterior pituitary

Question 9

What percent of the estrous cycle includes the follicular phase?

Answer 9

The follicular phase represents 20% of the estrous cycle. However, follicle growth and degeneration occurs continuously which leads to the spike of LH and FSH of the anterior pituitary

Question 10

How many antral follicles do pigs have?

Answer 10

50 small antral follicles / ovary

Question 11

What is recruitment in terms of follicular dynamics?

Answer 11

A cohort of small antral follicles and produce estrdiol

Some undergo antresia

Question 12

What is selection in terms of follicular dynamics?

Answer 12

a group of growing follicles which haven’t undergone atresia are selected

Involved emergence of dominant follicle(s) from cohort of already antral follicles - may become the dominant follicle or may undergo atresia

Continue to produce increasing amounts of estradiol and begin to produce a little inhibin

Question 13

What is dominance in terms of follicular dynamics?

Answer 13

One or more follicles exert an inhibitory effect on the other developing follicles

This is through to be caused by the production of inhibin and a reduce blood supply to some follicles

Question 14

What factors can promote atresia?

Answer 14

decreased FSH and decreased blood supply

Question 15

Atresia

Answer 15

In the medical literature, the term ‘ovarian follicular atresia’ refers to the degeneration and resorption of several follicles and their ovules (a form of apoptosis) prior to the maturation and release of one ovule from a healthy follicle. This term has been carried over to the context of oocytes in any animal system

Question 16

Hormone profiles of recruitment

Answer 16

increased FSH, decreased LH, no inhibin

Question 17

Hormone profiles of selection

Answer 17

Moderate FSH, moderate LH, decreased inhibin

Question 18

Hormone profiles of dominance

Answer 18

decreased FSH, increased LH, increased inhibin

Question 19

2 gonadotropin 2 cell theory

Answer 19

According to the two-cell–two-gonadotropin theory, luteinizing hormone stimulates thecal cells to produce androgens, and follicle-stimulating hormone stimulates granulosa cells to produce estrogens from androgens.