7 - Follicular Phase Flashcards
Six primary events of the follicular phase
- Elevated gonadotropin release (FSH & LH)
- Follicle growth & prep for ovulation
- Increase and peak in E2
- Sexual receptivity (estrus)
- LH surge
- Ovulation
Slide 6
The important diagram
Four processes of ovarian follicular development
- Recruitment
- Selection
- Dominance
- Atresia
What is recruitment
Small follicles begin to grow & produce E2
FSH is dominant hormone
What is selection
Selected follicle(s) proceed towards dominance (rest become atretic)
FSH + moderate LH & E2
What determines which follicles are recruited and which become atretic
Amount of receptors the follicle has for FSH (more = selected)
What is dominance
Dominant follicle(s) proceed to the point of ovulation & inhibit other follicles
LH & E2 + Inhibin
What is atresia
Degeneration & resorption of follicles that did not develop prior to ovulation
Slide 9-12
Follicular development diagrams ***
What are the roles of FSH and LH in follicular dynamics
There are stages dependent on each hormone
FSH dependent = recruited & early selected follicles
LH dependent = large selected & preovulatory follicles
What follicles become preovulatory?
Those with more LH receptors
Slides 14-16
Real follicles at different stages **
How many waves of follicular development are there?
Several occur during the Estrous cycle
What determines if a wave of follicular development reaches ovulation or not
Waves that occur during metestrus &/or diestrus (with high progesterone) will not reach ovulation; will be atretic & regress
Wave initiated during proestrus will develop into estrus stage and reach ovulation
Slide 18
Estrogen vs estradiol
Estrogen = substance (natural or synthetic) that exerts biological activity having an estrogenic effect (e.g. Estradiol, Estriol)
Estradiol = predominant estrogen produced by ovarian follicles during the estrous cycle
How is estradiol synthesized by the follicle (briefly)
Theca interna cell has receptor for LH
LH binds and protein kinase turns cholesterol into testosterone
Testosterone diffuses into granulosa cell, where FSH binds its receptor on the membrane
Protein kinase turns testosterone into Estradiol, which diffuses into the blood stream
Granulosa cells also…
develop LH-receptors preovulation
Estrogenic effects on the brain, hypothalamus
Brain = mating behaviour
Hypothalamus = increase GnRH = LH surge
Estrogenic effects on the reproductive tract
Increased:
- blood flow
- leukocytes (protect against foreign materials)
- mucosal secretion (vagina, cervix, uterus, oviduct)
- growth of uterine glands (secrete mucus)
- smooth muscle tone
- genital swelling
Slide 24
Steps to LH surge
