Menstrual cycle

Question 1

What happens if the ovulated secondary oocyte is unfertilized?

Answer 1

it degenerates and is shed along with the stratum functionalis of the endomet.

Question 2

Which germ cell is arrested in prophase I until the LH surge in ovulation?

Answer 2

Primary oocyte
- Diploid
- 2N, 4C
(46 sister chromatids are present)

Question 3

After meiosis I, are the secondary oocytes diploid or haploid?

What else is produced after meiosis I occurs?

Answer 3

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

Question 4

The secondary oocyte is arrested in meiosis II until when?

Answer 4

It is completed only if fertilization occurs

- gives rise to ovum and second polar bodies

Question 5

Difference between first and second polar body

Answer 5

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

Question 6

The terminology of Follicular phase and Luteal phase for the menstrual cycle is used in terms of what?

Answer 6

Ovarian fxn

• luteal phase is most consistent in duration
• formation of corpus luteum, regardless of fert

Question 7

The terminology of the Mentrual phase, the Proliferative phase, and the Secretory phase for the menstrual cycle is used in terms of what?

Answer 7

Endometrial activity

Question 8

Oocytes develop within a histologic unit known as the _____

Answer 8

ovarian follicle

Question 9

Preantral and antral follicles consist of what during follicular development?

Answer 9

Preantral

1. Primordial follicle
2. Primary follicle
3. Secondary follicle

Antral follicle

4. antral follicle
5. tertiary follicle
6. graafian follicle

Question 10

Do all follicles reach the antral stage each month?

Answer 10

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

Question 11

Once ovulation occurs, the resulting histologic unit in the ovary is the ________

Answer 11

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

Question 12

Locally mediated autocrine and paracrine factors in follicular maturation

Answer 12

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

Question 13

What aids to the more estrogenic microenvironment of the dominant follicle?

Answer 13

1. Better blood supply
   - increases delivery of FSH to follicle
2. More FSH receptors
3. More granulosa cell proliferation
4. More aromatase activity
   - more E production
5. 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

Question 14

When are primordial follicles completely formed?

Answer 14

6 months of life *frozen at prophase I

*only primordial follicle destined to ovulate becomes a primary follicle

Question 15

What does the primordial follicle consist of?

Answer 15

primary oocyte

surrounded by layer of pregranulosa cells

surrounded by basement membrane

*most follicles remain in this state (prevent atresia of oocyte)

Question 16

Only the primordial follicle destined to ovulate becomes a primary follicle. What does the primary follicle consist of?

Answer 16

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

Question 17

Secondary follicle consists of what?

Answer 17

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

Question 18

What change occurs in tertiary follicles (from secondary)?

Answer 18

FSH and estradiol cause the granulosa cells to proliferate + acquire LH receptors

2. Antrum develops in granulosa

Question 19

What does antral fluid contain?

Answer 19

estradiol
progesterone
androgens
inhibin
activin
FSH + LH

• all play a role in follicular development, ovulation, and modulation of hormonal responses.

Question 20

Corona radiata

Answer 20

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

Question 21

Cumulus oophorus

Answer 21

stalk that connects primary oocyte to remaining granulosa cells

*cumulus oophorus are located opp of the antrum

Question 22

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?

Answer 22

The cumulus oophorus breaks down and the oocyte, zona pellucida, and cumulus float within the enlarging follicle

• the follicle ruptures during ovulation!
• squish!

Question 23

What does the corpus luteum secrete?

Answer 23

estrogen and very high lvls of progesterone

- progesterone induces changes in the stratus functionalis which allows for successful implantation of fertilized ovum

Question 24

What happens to the corpus luteum and its progesterone secretion if fertilization occurs?

Answer 24

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

Question 25

What happens to the corpus luteum if fertilization does not occur?

Answer 25

*if fertilization does not occur, the CL regresses after 11 days --> reduction in progesterone --> disintegration and sloughing of endometrial stratum functionalis --> corpus luteum bcomes albicans (

Question 26

Pulsatile secretion of GnRH results in pulsatile release of LH and FSH. What inhibits LH pulses?

Answer 26

In the luteal phase, increasing progesterone lvls (from corpus luteum) will slow LH pulses.

Question 27

How does inhibin in the late follicular phase allow for the LH surge?

Answer 27

Inhibin enhances LH stimulation of the androgen synthesis in the theca (providing more E synth in granulosa cell) *inhibin also suppresses FSH secretion: ensures dominant follicle

Question 28

Estradiol is inhibitory at the level of hypothal and pit. at most [ ]s. When is this converted into a positive feedback mech?

Answer 28

High levels of estradiol (>200 pg/ml x 50 hours) --> stimulates LH surge *note that inhibin also stimulates LH surge by stimulating androgen synth in the theca

Question 29

Progesterone is inhibitory at _____ [ ]s, and stimulatory at _____ [ ]s.

Answer 29

high [ ] (like after ovulation) low [ ]s (like before ovulation) - progesterone facilitates the + feedback response of the pituitary to estradiol

Question 30

3 layers of endometrium

Answer 30

1. stratum basalis - deepest layer immediately adjacent to myometrium - doesnt change much during menses Stratum functionalis: 2. stratum spongiosum 3. stratum compactum

Question 31

Permanent stromal tissue of endometrium and contains bases of endometrial glands

Answer 31

stratum basalis

Question 32

Straight vs spiral arteries of the endometrium

Answer 32

Straight arteries: feed stromal layer of endometrium, does not go deep spiral arteries: - pass through basal layer into stratum functionalis - hormonally sensitive