Follicular Physiology/ Ovulation/ Luteolyis

Question 1

What are the 4 major events of the follicular phase ?

Answer 1

Rising level of gonadotropin from AP

Follicular growth/ prep for ovulation

Sexual receptivity

Ovulation

Question 2

What is the dominant hormone released during the follicular phase?

Answer 2

Estrogen

Question 3

How id proestrual follicular development initiated?

Answer 3

Leuteolysis leads to a decrease in progesterone

GnRH levels increase

FSH and LH levels increase

—> follicular development

Question 4

Follicles produce what hormones that feedback to the anterior pituitary?

Answer 4

Inhibin — negative feedback on FSH

Estradiol — positive feedback to surge center for release of GnRH, negative feedback at AP for FSH

This will lead to an LH surge —> ovulation

Question 5

What are the steps from the ovarian follicular pool that leads to an ovulatory follicle?

Answer 5

Recruitment (stimulated by FSH and LH)

Selection —> some of the recruited follicles will become atretic or progress further

Dominance — selected follicles that do not undergo atresia produce large quantities of E2

Ovulation

Question 6

What are the hormone levels of FSH, LH, inhibin and E2 during follicular recruitment?

Answer 6

FSH - high

LH - low

Inhibin — none

E2 — none

Question 7

What are the hormone levels of FSH, LH, inhibin and E2 during follicular selection?

Answer 7

FSH - low

LH- moderate

Inhibin — low

E2- low

Question 8

What are the hormone levels of FSH, LH, inhibin and E2 during follicular dominance ?

Answer 8

FSH - low

LH - high

Inhibin - high

E2- high

Question 9

Where does estrogen come from?

Answer 9

2-cell, 2-gonadotropin model

Theca interna cell turns cholesterol into testosterone

Granulosa cell uses testosterone to make estradiol

Question 10

LH binds to ________ cells resulting int he production of _________ hormone

Answer 10

Theca interna, testosterone

Question 11

FSH binds to ___________ cells resulting in production of __________ hormone

Answer 11

Granulosa cells, E2

Question 12

The preovulatory LH surge stimulates an increase in what hormones?

Answer 12

Increased PGE2
increased PGF2a
Progesterone

Question 13

An increase in PGF2a causes what?

Answer 13

Release of lysosomal enzymes —> follicle wall weakens

Increased contraction of ovarian smooth muscle —> increased follicular pressure

Ovulation

Question 14

The primordial germ cells have how many chromosomes ?

Answer 14

2N (diploid)

Question 15

Primary oocytes have how many chromosomes?

Answer 15

2N (diploid) —> 4N with arrest at first meiotic prophase (arrested here until LH surge )

Question 16

Secondary oocyte has now many pairs of chromosomes?

Answer 16

2N with 1st polar body (following first meiotic divisions)

Question 17

At the time of ovulation how many chromosome pairs are in the oocyte?

Answer 17

1N with 2 polar bodies

Question 18

What is an induced ovulator?

Answer 18

Requires stimulation of the vagina and/or cervix for ovulation to occur

Sensory neurons within the vagina and at the cervix sense copulation and relay this signal to the surge center —> GnRH release —>LH release —> ovulation

Question 19

What is the duration of the LH surge in most speices?

Answer 19

24hrs

Except in mares where it is elevated form 3-5days

Question 20

T/F: All animal except the cow ovulate during estrus, except the cow

Answer 20

True

Eg bitch ovulates 2-3days after LH surge

Question 21

What occurs to the follicle following ovulation

Answer 21

Collapses

Fills with blood — corpus hemorrhagicum

Question 22

Most species ovulate a secondary oocyte, except __________ who will ovulate a primary oocyte

Answer 22

Canids

Question 23

What two phases of the estrous cycle occur during the luteal phase?

Answer 23

Metestrus and diestrus

Question 24

What are the 3 main events of the luteal phase?

Answer 24

Lutenization of follicular cells to luteal cells

Growth/development of CL —>progesterone production

Luteolysis

Question 25

What is the process of lutenization?

Answer 25

Transformation of the theca interna cells into small luteal cells and granulosa cells into large luteal cells —> producing progesterone

Question 26

What other hormones besides progesterone does the CL produce?

Answer 26

Oxytocin

Relaxin

Question 27

What are the physiological effects of progesterone?

Answer 27

Hypothalamus — neg feedback, decrease GnRH

Anterior pituitary — neg feedback

Uterus — positive influence on uterine glands to secrete “uterine milk” for potential concepts, reduces myometrial tone

Mammary glands — prior to parturition causes final alveolar development

Question 28

What is luteolysis?

Answer 28

Disintegration of the CL

—> dramatic drop in progesterone (1-3days)

Question 29

What is the luteolytic agent in domestic animals and where does it come form?

Answer 29

PGF2a

Uterine endometrium (except in dog)

Question 30

How does PGF2a get from the uterus to the ovaries in ruminant vs mare vs sow?

Answer 30

Ruminant — local countercurrent exchange from ipsilateral uterine vein to ovarian artery in ruminants

Mare — systemic

Sow— combination of the both

Question 31

When do oxytocin receptors appear in the endometrium?

Answer 31

10-14days of increasing P4

CL contains large amounts of oxytocin
Oxytocin release stimulates a pulse of PGF release —> oxytocin release (positive feedback)