Female Repro Flashcards
GnRH secretion in the female lifespan
> What happens if the GnRH pulses are the same all throughout?
> What regulates GnRH secretion?
> Importance of GnRH pulses?
> Slow pulses stimulate secretion of? Fast pulses?
During the juvenile period, there’s no GnRH pulses because they are highly inhibited but in the peripubertal and pubertal period, you now have GnRH pulses that are more regular.
During ovulatory period, there’s a larger pulse
> What happens if the GnRH pulses are the same all throughout?
-There’ll be now LH surge during ovulation so you will not have the release of ovum.
>Regulation: Kisspeptin neurons Arcuate kisspeptin neurons: Stimulatory Preoptic kisspeptin neurons: Inhibitory *This is in the rats In humans, it’s in the infundibulum (stimulatory) and preoptic (inhibitory)
> Importance:
Pulses of GnRH drive the secretion of LH and FSH which will drive the secretion of progesterone and estrogen, respectively.
> Slow pulses = LH; Fast pulses = FSH
Folliculogenesis
You start with 7 million then before birth it declines and around puberty it goes down to 300k-400k and decreases further as you age.
Number of primordial follicles decreases progressively as a consequence of recruitment
Oogenesis
> equivalent of spermatogenesis in males; gametogenesis
> You have oogonia (SCs which divide via mitosis) —> 1’ oocyte which are arrested in the diplotene stage of the prophase I of meiosis I up until puberty -> During puberty, it will resume. The LH surge causes ovulation -> formation of 2’ oocyte which is arrested at metaphase II until sperm penetration of the egg when it finally completes meiosis
Development of the mature Graafian follicle
1st phase: Preantral phase or gonadotropin-independent phase
>Growth and dx of the oocyte from the oogonia to the 2’ follicle
>Cuboidal granulosa cells appear and they proliferate up until they become multilayered epithelium (2’ follicle) -> once it’s 3-6 layers, granulosa cells secrete hormones that work in a paracrine manner/paracrine factors which are important to form preantral follicle
>Mature preantral follicle will form your proteins that make the zona pellucida
>Follicles develop from primordial to primary to 2’ before acquiring an antral cavity
>NOT DEPENDENT ON FSH
2nd phase: Antral or Gonadotropin-dependent phase
>characterized by tremendous increase of the follicular size (takes about 25 days to develop)
>The increase of the granulosa cells make it form 2 groups:
1. Stratum granulosum
2. Cumulus cells
Pre-antral to Antral follicles
- Main factor for the selection of follicles
- What will tell your other follicles that one of the follicles has already seveloped/became 3’ follicle?
- FSH receptors
- Presence of antrum. Activin A is produced by the granulosa to inhibit further devt of primordial follicles AND mural granulosa cells will produce inhibin B which will stop further release of FSH
Folliculogenesis
- Occurs where?
- Four developmental stages in folliculogenesis?
- Cortex of the ovary
2.a. Follicular recruitment or primordial follicle activation
B. Preantral follicle development
C. Selection and growth of antral follicle that will eventually become you Graafian follicle
D. Follicle atresia
Initial vs. Cyclic Recruitment of Ovarian Follicles - in terms of the ff:
- Stages
- Hormones involved
- Default pathway
- Timing
- Oocyte status
Initial Recruitment:
- Stages: Primordial
- Hormones involved: not determined
- Default pathway: Remain dormant
- Timing: Continuous throughout life, begins after follicle formation
- Oocyte status: Starting to grow, not capable of undergoing geminal vesicle breakdown
Cyclic recruitment:
- Stages: Antral
- Hormones involved: FSH
- Default pathway: Apoptosis
- Timing: Cylic
- Oocyte status: complete growth; competent to undergo germinal vesicle breakdown
What is the “2 cell, 2 gonadotropin” theory?
The follicle is a temporary endocrine organ because it dies but it produces hormones.
>2 gonadotropin: LH and FSH
>2 cell: theca and granulosa cell
>As mentioned earlier, initially you have granulosa cells which when it reaches 3-6 layers, some will flatten and become your theca cells. The theca cells, then, respond to LH.
>And what happens here is the cell starts to produce the enzymes necessary to convert cholesterol to pregnenolone all the way to androstenedione and the latter crosses that BM to now go to the granulosa cell which has FSHr which will make the enzymes necessary to will convert androstenedione to estradiol and estradiol goes to the blood which has an effect on the uterus.
Menstrual cycle
- What is it?
- Phases
- Menstrual cycle occurring at less than 21 days interval? More than 35 days?
- Cyclic, orderly sloughing off of the functional layer of the endometrium due to estrogen and progesterone
- Phases:
A. Follicular
B. Luteal
*These refer to changes in the follicle NOT the uterus - Less than 21 = polymenorrhea
More than 35 = Oligomenorrhea
GnRH pulses
> Become very rapid during the time you have more LH secretion
After the ovulation has occurred, during LUTEAL phase, GnRH pulses slow down
Effects of FSH
- Granulosa cell proliferation and dx
- Antral follicle development
- Estrogen production (produces a positive feedback on LH)
- Induction of LH receptors on the dominant follicle
- Stimulate the production of inhibin by granulosa cells to inhibit FSH release
Follicular phase
- When does it happen?
- Development is dependent on?
- What happens?
- FSH trend here
- LH trend here
> From 1st day of menses to the production of mature Graafian follicle
> Development is dependent on the no. of FSHr in the granulosa cells of that developing follicle
> Inc granulosa cells -> inc estradiol -> cause eventual restruction of endometrium to proliferate and divide to replace the cells shed off
> FSH is elevated in the follicular phase then declines until ovulation where you have inc again
> LH is low in the early follicular phase and starts to rise mid cycle
Stages of development of the dominant follicle
- Recruitment
- Selection
- Dominance
Ovulation
- Happens when?
- Why does the LH surge happen?
- 10-12 hrs after LH peaks
- Increasing levels of estradiol causes a positive feedback on the AP that makes it more responsive to GnRH -> LH surge stimulate luteinization of the granulosa cells -> once there’s more lutein cells than granulosa cells, progesterone will be secreted more
Luteal phase
- Span
- If you are a 35-day cycle female, which period is longer - follicular or luteal?
- Usually 14 days long
2. Follicular
