7 – Female Reproduction II

Question 1

Follicular dynamics: continuous

Answer 1

• Follicular growth and regression is a continuous process
• Independent of the phase of the reproductive cycle
• Not synchronized

Question 2

Follicular dynamics: wave pattern

Answer 2

• Reservoir of antral follicles in a resting stage
• At a particular time (species dependent) one will grow and reach maturity during estrus
• *greater than 95% of bovine estrous cycles are composed of either 2 or 3 follicular waves

Question 3

Estrus cycle

Answer 3

• Duration between 2 estrus (heats)
• Bovine=23 days

Question 4

Dynamics of follicles consist of:

Answer 4

1. Recruitment
2. Selection
3. Dominance
   a. Polytocous species=multiple dominant follicles)
4. Atresia
   *synchronized by interaction of 4 hormones

Question 5

4 hormones that are synchronized

Answer 5

• FSH
• LH
• Estradiol
• P4 (progesterone)
• *2 negative, 1 positive feedbacks

Question 6

What controls GnRH release?

Answer 6

• Tonic and surge centers in hypothalamus
• Release of FSH and LH

Question 7

Release of GnRH from tonic center neurons

Answer 7

• Occurs spontaneously in a rhythmic fashion
• Always activated
• Does not have HIGH concentration

Question 8

Release of GnRH from surge centre

Answer 8

• Controlled by HIGH ESTROGEN
  o From growing antral follicles in form of estradiol
• HIGH production of GnRH=high production of LH (LH surge)
• Accompanied by low progesterone (from CL)

Question 9

Role of progesterone

Answer 9

• Essential to turn on surge center to achieve ovulation

Question 10

Recruitment of follicles

Answer 10

• Phase of follicular development in which cohort of small antral follicles begin to GROW

Question 11

What precedes a follicular wave?

Answer 11

• Surge of plasma FSH from tonic centre

Question 12

Selection of follicles

Answer 12

• Selected and either become atretic or develop further
• Some follicles start shifting their dependence from FSH to LH=acquire LH responsiveness

Question 13

Low estradiol concentrations

Answer 13

• Negative feedback on hypothalamus so follicular wave can finish
  o Don’t need more FSH and LH

Question 14

Dominant follicle

Answer 14

• One that reaches the largest diameter
• Produces increasing amounts of estradiol=positive feedback to A. pituitary

Question 15

How does the dominant follicle become dominant?

Answer 15

• FSH starts follicular wave
• Post surge decline of FSH, growth of most follicles of a wave stop and begin to regress
• *Maintains growth by transitioning dependence from FSH to LH

Question 16

What happens once estradiol (from dominant follicle) reaches threshold level?

Answer 16

• Negative to positive feedback of GnRH=surge of LH=OVULATION

Question 17

Peak estradiol concentration in follicular fluid of ovulatory follicle compared to anovulatory dominant follicles

Answer 17

• Twice as high

Question 18

What happens at ovulation?

Answer 18

• Antral contents are evacuated
• Wall of ovulatory follicle collapses =CL
• CL produces progesterone

Question 19

What is plasma progesterone concentration highly correlated with?

Answer 19

• CL weight and volume
• *if increased=inhibits SURGE center

Question 20

What happens when there is high progesterone from CL?

Answer 20

• Tonic centre release GnRH
• FSH
• Growing follicles produce estradiol
• Estradiol effect on SURGE centre is blunted
• No LH surge
• No ovulation

Question 21

What happens when there is low progesterone from CL?

Answer 21

• Tonic centre release GnRH
• FSH
• Growing follicles produce estradiol
• Estradiol is above threshold and activates SURGE centre
• LH surge
• Ovulation

Question 23

Endogenous (or exogenous) progesterone in pregnant cows

Answer 23

• Regular emergence of anovulatory follicular waves (tonic center is always activated)
• Dose-related suppression of LH and dominant follicle growth
• Max follicle diameter and intra-wave interval decreases
  *High progesterone (since pregnant)=inhibits surge center (eventually slightly decreases tonic centre)
• Follicular wave through gestation EXCEPT LAST 21 days

Question 24

Luteolysis

Answer 24

• when pregnancy does NOT occur
• caused by prostaglandin F2-alpha

Question 25

Prostaglandin F2-alpha

Answer 25

* released from endometrium around day 17-19 of cows estrous cycle

Question 26

Prostaglandin F2-alpha: mares

Answer 26

* systemic route

Question 27

Prostaglandin F2-alpha: ruminants

Answer 27

* local route

Question 28

Prostaglandin F2-alpha: pigs and camelids

Answer 28

* both local and systemic

Question 29

Prostaglandin F2-alpha: dogs

Answer 29

* similar profile in pregnant and non-pregnant * pseudopregnancy: drops slowly * pregnant: drops suddenly

Question 30

Prepubertal calves

Answer 30

* Regular emergence of anovulatory follicular waves

Question 31

Regular emergence of anovulatory follicular waves in prepubertal calves

Answer 31

1. FSH surges coupled to wave emergence 2. Follicle dominance increases with age 3. Max follicular diameter and intra-wave interval (IWI) increase with age 4. Circulating LH concentration increases with age

Question 32

First ovulatory cycle is short

Answer 32

* 8 days * Short-lived, under-developed CL * 1 follicular wave

Question 33

What starts the follicular wave?

Answer 33

* FSH

Question 34

2-wave vs. 3-wave patterns: difference

Answer 34

* Duration of cycle (19-20 or 22-23 days) * Interwave interval (10 or 8 days) * Max size of 2nd dom. Follicle (15 or 13 mm) * Onset of luteolysis (day 16 or 18) *pregnancy rate is the same

Question 35

Wave emergence size

Answer 35

* 1mm * Dominant follicle emerges 6-12hrs earlier than first subordinate follicle

Question 36

Reproductive senescence

Answer 36

* Gradual decline in reproductive capacity with age * Continued 2/3 wave patterns * Elevated FSH * Interovulatory and interwave interval do not change * CL smaller=lower progesterone * Fewer follicles at wave emergence * Lower super stimulatory response * Lower fertilization rate

Question 37

Mother vs. daughter pairs

Answer 37

* Have same 2- or 3- wave pattern