Follicular Physiology, Ovulation, Luteinization, Luteolysis

Question 1

What process of follicular dynamics is characterized by high FSH, low LH, no inhibin, and no E2?

Answer 1

recruitment

Question 2

T/F: The sow ovulates a primary oocyte

Answer 2

False

The dog ovulates a primary oocyte​

Question 3

What is the dominant hormone during the luteal phase?

Answer 3

progesterone

Question 4

Ovulation typically occurs during estrus, except in __________

Answer 4

cows

Usually a 12-hour period. If you see them in heat, you breed them 12 hours later

Question 5

Describe the hormonal pre-ovulatory events that occur, starting with a decrease in progesterone (due to luteolysis):

Answer 5

• Decrease in P4 due to luteolysis
• Release of negative feedback of P4 at hypothalamus, which increases GnRH, increasing FSH and LH
• Developing follicle increases estrogen and inhibin production
  
  • Estrogen sends positive feedback to the surge center, resulting in even more release of GnRH
  • Simultaneously, inhibin and estrogen send negative feedback to FSH in the anterior pituitary, resulting in a huge amount of LH
• Preovulatory LH surge
• Boom.

Question 6

Which of the following is seasonally polyestrus:

• Horse
• Cow
• Sow
• Dog

Answer 6

Horse

Question 7

T/F: Progesterone induces luteolysis

Answer 7

False

Question 8

Degeneration of antral follicles is termed:

Answer 8

atresia

Question 9

What are the 3 main events that occur during the luteal phase?

Answer 9

• Luteinization of follicular cells to luteal cells
• Growth/development of CL ∴ production of P4
• Luteolysis

Question 10

What is the dominant hormone during the follicular phase of the estrous cycle?

Answer 10

Estrogen

Question 11

The bitch ovulates _____ days after LH surge

Answer 11

2-3 days

Question 12

What are the four major events during the follicular phase of the estrous cycle?

Answer 12

1. Rising levels of gonadotropin release from anterior pituitary
2. Follicular growth/prep for ovulation
3. Sexual receptivity
4. Ovulation

Question 13

What stages of the estrous cycle are involved in the follicular phase?

Answer 13

proestrus and estrus

Question 14

Pathways to luteolysis vary by species. Luteolysis occurs via only a systemic pathway in __________

Answer 14

mares

How does PGF_2a get from the uterus to the ovary? Prostaglandin PGF_2a​ from the uterus is transported to the ipsilateral ovary through a vascular countercurrent exchange mechanism. The countercurrent diffusion system is present in the cow, sow, and ewe, but not in the mare.

Question 15

The key player in luteolysis is:

Answer 15

PGF_2a

Generally uterine endometrium is the source of PGF_2a in domestic animals

Question 16

Which stages of the estrous cycle are involved in the luteal phase?

Answer 16

metestrus and diestrus

Question 17

Luteinization is the transformation of the theca interna and granulosa cells of the follicle to luteal cells producing P4. Granulosa cells become __________ and theca interna cells become __________

Answer 17

Luteinization is the transformation of the theca interna and granulosa cells of the follicle to luteal cells producing P4. Granulosa cells become large luteal cells and theca interna cells become small luteal cells

Question 18

Positive feedback from what hormone causes GnRH release from the surge center?

• Progesterone
• Estrogen
• FSH
• LH

Answer 18

Estrogen

Question 19

Which of the following is not an important event during the follicular phase of the ovary?

• Elevated GnRH release from pituitary
• Preparation for ovulation
• Sexual receptivity
• LH surge
• Progesterone secretion

Answer 19

Progesterone secretion​

Question 20

What process of follicular dynamics is characterized by low FSH, high LH, and high inhibin?

Answer 20

dominance

Question 21

___________ refers to decomposition of the corpus luteum

Answer 21

Luteolysis refers to decomposition of the corpus luteum.

It occurs during a 1-3 day period at the end of the luteal phase. If luteolysis does not occur, the animal will remain in a sustained luteal phase because progesterone inhibits gonadotropin secretion

Question 22

T/F: Progesterone blocks the preovulatory LH surge

Answer 22

True

Question 23

T/F: Progesterone increases basal GnRH amplitude and frequency

Answer 23

False

Question 24

T/F: Elevated GnRH is essential for initiating the follicular phase of the estrous cycle

Answer 24

True

Question 25

__________ ovulators require stimulation of the vagina and/or cervix for ovulation to occur

Answer 25

induced ovulators

• Rabbits, minks, ferrets, giant fruit bats, cats, the 13 –lined ground squirrel, Sumatran rhinos
• Camelids appear to also require a substance in seminal plasma for ovulation
• Cats have a 50% of ovulation if mated once
• Lions have been reported to mate more than 100 times during the 2-4 day estrus cycle.

Question 26

During the follicular phase, the tonic center of the hypothalamus releases small pulses of GnRH that stimulate release of __________ from the anterior pituitary

Answer 26

FSH and LH

This causes growth and development of follicles on the ovary. The follicles produce estrogen.

Question 27

During the recruitment phase of follicular development, which hormone is dominant?

• FSH
• LH
• Inhibin
• Estrogen

Answer 27

FSH

Question 28

What physiologic effect does progesterone have on uterine tone?

Answer 28

causes relaxation of the uterus

Question 29

The surge center of the hypothalamus responds in a positive-feedback-fashion to increasing levels of __________ in absence of __________ to release large quantities of GnRH

Answer 29

The surge center of the hypothalamus responds in a positive-feedback-fashion to increasing levels of estrogen (produced by follicle) in absence of progesterone to release large quantities of GnRH

• This causes release of LH and leads to ovulation*
• **The surge center is “turned on” once estrogen reaches threshold level***

Question 30

The cells of the theca interna contain receptors for LH. Thecal cells produce __________ that diffuses into the granulosal cells that contain FSH receptors.

Answer 30

The cells of the theca interna contain receptors for LH. Thecal cells produce testosterone that diffuses into the granulosal cells that contain FSH receptors.

Binding of FSH to the granulosal cell receptors causes the synthesis of enzymes that are responsible for the conversion of testosterone to estradiol