Female Cyclicity

Question 1

What are the dominant ovarian structures and dominant hormone in the follicular phase?

Answer 1

follicles

estrogen

Question 2

What are the dominant ovarian structures and dominant hormone in the luteal phase?

Answer 2

corpus lutea

progesterone

Question 3

At which day is there maternal recognition of pregnancy?

Answer 3

day 16

Question 4

What is happening in proestrus?

Answer 4

• begins when P4 drops as a result of luteloysis
• ends at the onset of estrus
• formation of ovulatory follicles and E2 secretion begins

Question 5

What is happening in metestrus?

Answer 5

• CL formation

- beginning of P4 secretion

Question 6

What is happening in diestrus?

Answer 6

• sustained secretion of high levels of P4 form mature CL

- ends with luteolysis

Question 7

What are the four major events in the follicular phase?

Answer 7

• rising levels of gonadotropin release from anterior pituitary
• follicular growth/pre for ovulation
• sexual receptivity
• ovulation

Question 8

Describe the action of the tonic center

Answer 8

• releases small pulses of GnRH that stimulate release of FSH and LH from anterior pituitary
• causes growth and development of follicles

Question 9

Describe the action of the surge center

Answer 9

• releases large quantities of GnRH in response to increasing estrogen levels
• causes release of LH, resulting in ovulation

Question 10

Describe the hormone levels in the recruitment phase

Answer 10

high FSH
low LH
no inhibin
no E2

Question 11

Describe the hormone levels in the selection phase

Answer 11

low FSH
moderate LH
low inhibin

Question 12

Describe the hormone levels in the dominance phase

Answer 12

low FSH
high LH
high inhibin

Question 13

Describe the 2-cell, 2-gonadotropin model of estrogen production

Answer 13

• LH binding to theca interna cells results in production of testosterone
• testosterone enters the granulosa cells
• when FSH binds to the granulosa cells, it causes conversion of testosterone to estrogen

Question 14

What are the 3 main events of the luteal phase?

Answer 14

• lutenization of follicular cells to luteal cells
• growth/development of CL leading to production of P4
• luteolysis

Question 15

What is lutenization?

Answer 15

transformation of theca interna and granulosa cells of the follicle to luteal cells producing P4

Question 16

What are the effects of progesterone on the hypothalamus?

Answer 16

• reduces GnRH
• prevents behavioral estrus
• stops pre-ovulatory LH surge

Question 17

What is the effect of progesterone on the anterior pituitary?

Answer 17

suppression of LH and FSH

Question 18

What are the effects of progesterone on the uterus?

Answer 18

• positive influence on uterine glands to secrete “uterine milk” for potential conceptus
• reduces myometrial tone

Question 19

What is the luteolytic agent in domestic animals, and what is the source?

Answer 19

PGF2a

- uterine endometrium

Question 20

What are the pathways of luteolysis?

Answer 20

• countercurrent exchange of PGF2a from uterine vein and ovarian artery in ruminants
• systemic pathway in mare
• combination in sows

Question 21

Describe the hormonal induction of luteolysis

Answer 21

• oxytocin receptors appear in endometrium in late luteal phase
• CL contains large amounts of oxytocin
• Oxytocin release stimulates pulse of PGF2a release
• PGF2a stimulates more oxytocin
• positive feedback system