Exam 2: Estrous Cycles, Follicular Phase Flashcards
Steps of the Preovulatory LH Surge
↓ P4 from CL
↑ GnRH
↑ FSH and LH
Proestual follicular development
↑ inhibin > ↓ FSH
↑ estradiol –> preovulatory LH surge
Follicular Dynamics
Process of follicular growth and degeneration
Involves LH and FSH
Occur continuously throughout the entire estrous cycle
Antral follicle
4 dynamics of antral follicles
Steps of folliculogenesis
Recruitment
Selection
Dominance
Atresia
Folliculogenesis
Begins with recruitment (activation) of a primordial follicles into pool of growing
Ends with ovulation or atresia
Stages of folliculogenesis
Preantral/gonadotropin-independent phase: growth and differentiation of the oocyte
Antral/gonadotropin-dependent phase: increase in the size of the follicle
Recruitment
Small antral follicles recruited from the ovarian pool and produce small amounts of Estradiol
Selection
Follicles are selected from previously recruited small follicles and either become atretic or develop further Selected follicles produce moderate amounts of Estradiol
Dominance
Selected follicles that do not become atretic become dominant: produce high quantities of Estradiol & will ovulate
In polytocous species, more than one follicle is selected, in monotocous species one follicle is selected
Atresia
Death of follicles
Hormones in selection
low FSH
moderate LH
low inhibin
moderate estradiol
Hormones in recruitment
high FSH
low LH
no inhibin
low estradiol
Hormones in dominance
low FSH
high LH
high inhibin
high estradiol
Follicular waves
2 or 3 waves of folliculogenesis occur during one estrous cycle
Only the wave that occurs during proestrus and estrus (after luteolysis) will result in ovulation
Atresia
Reduced FSH concentrations in blood coupled with reduced blood supply to some follicles results in atresia
Occurs continuously during folliculogenesis
Over 90 % of ovarian follicles undergo atresia
Word atresia refers to closure of antrum
What causes menopause
Depletion of follicles
Changes that occur during menopause
Ovarian function ceases, reduction in estrogen, progesterone, and inhibin
Dramatic decline in follicular/oocyte numbes, leads to decrease estrogen in blood
No follicles –> inhibin cannot be secreted, FSH levels increase to 20-30x
No LH surge because estrogens do not peak to cause GnRH surge
2 cell, 2 gonadotropin model
(understand the diagram)
Important step in preparation of follicle for ovulation:
Expression of LH receptors by granulosa cells
When LH receptors are present, preovulatory LH surge can exert its full effect on the follicle to cause ovulation
Targets of estrogen
Increased blood flow
Genital swelling
Change in tissue electrical conductivity
Leukocytosis
Increased mucosal secretion
Initiation of uterine gland growth
Elevated myometrial tone
