Menstrual cycle Flashcards
What happens if the ovulated secondary oocyte is unfertilized?
it degenerates and is shed along with the stratum functionalis of the endomet.
Which germ cell is arrested in prophase I until the LH surge in ovulation?
Primary oocyte
- Diploid
- 2N, 4C
(46 sister chromatids are present)
After meiosis I, are the secondary oocytes diploid or haploid?
What else is produced after meiosis I occurs?
Haploid
1N, 2C
- reduction in number of chromosomes from diploid complement (46 sister chromatids) to haploid complement (23 sister chromatids)
First polar body
*note that sec. oocyte contains majority of cytoplasm
The secondary oocyte is arrested in meiosis II until when?
It is completed only if fertilization occurs
- gives rise to ovum and second polar bodies
Difference between first and second polar body
first and second both contains 23 chromosomes (1N)
first: 23 chromosomes contain duplicated DNA (2C)
second: 23 chromosomes contain non-duplicated DNA (1C)
* technically the first polar body can degenerate or divide again
The terminology of Follicular phase and Luteal phase for the menstrual cycle is used in terms of what?
Ovarian fxn
- luteal phase is most consistent in duration
- formation of corpus luteum, regardless of fert
The terminology of the Mentrual phase, the Proliferative phase, and the Secretory phase for the menstrual cycle is used in terms of what?
Endometrial activity
Oocytes develop within a histologic unit known as the _____
ovarian follicle
Preantral and antral follicles consist of what during follicular development?
Preantral
- Primordial follicle
- Primary follicle
- Secondary follicle
Antral follicle
- antral follicle
- tertiary follicle
- graafian follicle
Do all follicles reach the antral stage each month?
no just 10-30 who happen to be in right place at right time.
But only 1 reaches dominance each cycle –> becomes antral fol –> ovulates
Once ovulation occurs, the resulting histologic unit in the ovary is the ________
corpus luteum
- remaining shell of dominant follicle
- one of the most vascular tissues in the body
- this regression happens even if fertilization doesnt take place
- no longer contains oocyte
Locally mediated autocrine and paracrine factors in follicular maturation
Inhibin: inhibits FSH (help dom fol)
Activin: augments FSH
Interleukin
Growth factors
*ie: VEGF is produced by granulosa cells in response to LH and induces angiogenesis in developing follicle
What aids to the more estrogenic microenvironment of the dominant follicle?
- Better blood supply
- increases delivery of FSH to follicle - More FSH receptors
- More granulosa cell proliferation
- More aromatase activity
- more E production - More Inhibin production from the dominant follicle
- rising E and Inhibin [ ] exert (-) feedback on subsequent FSH secretion –> widening gap btwn itself and other non-dominant follicles in its cohort
When are primordial follicles completely formed?
6 months of life *frozen at prophase I
*only primordial follicle destined to ovulate becomes a primary follicle
What does the primordial follicle consist of?
primary oocyte
surrounded by layer of pregranulosa cells
surrounded by basement membrane
*most follicles remain in this state (prevent atresia of oocyte)
Only the primordial follicle destined to ovulate becomes a primary follicle. What does the primary follicle consist of?
Larger primary oocyte
- surrounded by zona pellucida layer
- facilitates sperm attachment to and fertilization of secondary oocyte
surrounded by single layer granulosa cells
surrounded by BM
*only thing thats new is ZP
Secondary follicle consists of what?
primary oocyte
surrounded by ZP
- surrounded by several layers of granulosa cells
- they acquire receptors for FSH, androgens, and E, and become hormonally active
surrounded by bm
- adjacent stromal tissue differentiates into theca cells
- theca cells develop LH receptors and begin to synth. steroids.
*vascular supply to the area increases
What change occurs in tertiary follicles (from secondary)?
FSH and estradiol cause the granulosa cells to proliferate + acquire LH receptors
- Antrum develops in granulosa
What does antral fluid contain?
estradiol progesterone androgens inhibin activin FSH + LH
- all play a role in follicular development, ovulation, and modulation of hormonal responses.
Corona radiata
Seen in the secondary or Graafian or antral follicle
Inner layer of granulosa cells surround the oocyte
- starts becoming enveloped by antral fluid
*see image in handouts
Cumulus oophorus
stalk that connects primary oocyte to remaining granulosa cells
*cumulus oophorus are located opp of the antrum
Just prior to ovulation, the first meiotic division is completed, giving rise to secondary oocyte and first polar body.
What else occurs jsut prior to ovulation?
The cumulus oophorus breaks down and the oocyte, zona pellucida, and cumulus float within the enlarging follicle
- the follicle ruptures during ovulation!
- squish!
What does the corpus luteum secrete?
estrogen and very high lvls of progesterone
- progesterone induces changes in the stratus functionalis which allows for successful implantation of fertilized ovum
What happens to the corpus luteum and its progesterone secretion if fertilization occurs?
hCG secreted by conceptus maintains it for ~ 9 weeks until placenta is able to independently produce progesterone
*if fertilization does not occur, the CL regresses after 11 days
