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GIGU Final > Menstrual cycle and ovulation > Flashcards

Menstrual cycle and ovulation Flashcards

1
Q

During fetal development what phase are follicles arrested in?

A

Meiosis I Prophase, until the LH surge

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2
Q

When does the seocnd meiotic arrest occur?

A

Metaphase II due to elevated MAPK proteins

  • Only resumes meiosis II when/if fertilization occurs
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3
Q

What are the three stages of the ovarian follicle cycle?

A
  1. Follicular phae
  2. Ovulatory phase
  3. Luteal phase
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4
Q

Describe the follicular phase

A
  • Ovarian follicle: the fxnl unit of the ovary it performs gametogeic and endocrine fxns
  • Premenopausal cycling ovary contains follicular structures at different stages
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5
Q

Describe the primordial follicle.

A
  • Primary oocyte arrested in the first meiotic phase, surrounded by a single layer of pergranulosa cells
  • It releases paracrine factors and NO steroid hormones
  • Represents the ovarian reserve, most of these will undergo atresia
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6
Q

Describe a primary follicle.

A
  • Central primary oocyte found in the center with a single layer of granulosa cuboidal cells
  • Incerease in size of the folicle occurs due to the growth of the primary oocyte
  • Early production of glycoproteins ZP1,2,3,4
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7
Q

Describe a secondary follicle.

A
  • Primary oocyte surrounded by 3-6 layers of cuboidal granulosa cells
  • Secretion of paracrine factors occurs inducing local stroma cells to differentiate into the thecal ccells
    • inner thecal cells are glandular and highly vascular
    • Fibrous apsule like theca externa
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8
Q

What occurs around the follicle as it progresses to a secondary follicle and what does it allow for?

A
  • Increase in vascularization around the follicle
  • Follicles release angiogenic factors creating the vasculature wreath around the follicle providing nutrients for follicle
  • ZP also develops providing binding sites for sperm
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9
Q

What are the fxns of preantral follicle cells?

A

Minimal endocrine fxn

  • granulosa cells express FSH receptors but are dependent ono paracrine factors from oocyte for growth
  • Granulosa cells aren’t producing ovarian hormones yet
  • Thecal cells are aalagous to leydig cells expressing LH producing androstenedione
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10
Q

what marks the antral phase in follicular phase of ovarian cycle?

A
  • appearance of antrum
  • oocyte becomes suspended in fluid surroundeed by the cumulus oophorus
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11
Q

What oes an increase in follicular size depend on?

A
  • Increase in antral size
  • Volume of follicular fluid
  • Proliferation nof granulosa cells
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12
Q

What are mural granulosa cells?

A
  • Makes up outer wall of the follicle and becomes highly steroidogenic
  • aka stratum granulosum
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13
Q

What are cumulus oophorus/radiata cells?

A
  • Mainatain gap and adhesion jxns with oocyte
  • released during ovulation with oocyte
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14
Q

What are thecal cells in the mid antral follicle growth responsive to?

A

LH,, this causes them to synthesize androgens from acetate and cholesterol

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15
Q

What are granulosa cells in the mid antral follicle growth responsive to?

A
  • FSH
  • COnverts the androges from the thecal cells into estrogens with aromatase
  • Induces expression of LH receptors in the late follicular phase
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16
Q

When does the oocyte become competent to complete meiosis I?

A

Antral stage

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17
Q

What allows meiotic arrest to occur?

A

Maintenance of elevated cAMP

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18
Q

How does sensitivity to FSH aid in selection of follicles?

A
  • During the follicular phase FSH levels begin to decline due to inhibin and estrogen being produced by the mural granulosa cells
  • The largest follicle with the most FSH receptors will become the dominant follicle and the rest undergoes atresia
19
Q

What is the preovulatory period?

A
  • Time from onset of LH surge to ovulation where structural chages occur in preparation for ovulation
  • CHanges in the sterroidogenic fxn of theca and mural granulosa cells occurs, preping for luteinization, CL formation, and increasing progesterone production
20
Q

How does the LH surge impact granulosa cells?

A

Causes differentiation of granulosa cells into granulosa lutein cells

  • thecal and mural granulosa cells will express LH receptors at the surge
  • Inhibition of aromatase expression occurs decreasing the positive feedback on LH secretion
  • Increases vascularization of granulosa
21
Q

What structural changes does LH surge induce?

A
  • breakdown follicle wall tunica albuginea and surface epithelium via release of cytokines and hydrolytic enzymes from theca and granulosa
  • Cumulus oocyte complex becomes free floating in the antrum
  • Basal lamina of mural granulosa cells is degraded and increased blood supply to follicle/ CL occurs
  • LH surge induces oocyte to pregress to metaphase II
22
Q

What is the luteal phase?

A
  • Antral cavity fills with blood and cell debris called corpus hemorrhagicum
    • granulosa lutein cells collapse into antral cavity
    • filledd with cholesterol esters
    • theca blood vessels and WBC fill rest of cavity
23
Q

Describe the corpus luteum.

A
  • Corpus luteum of menstruation lasts for 14 days if no pregnancy occurs and then becomes the corpus albicans
  • IF pregnancy occurs it is saved by hCG and it stays throughout pregnancy
24
Q

What does CL do for pregnancy?

A
  • Produces increasing aamounts of progesterone transforming uterine lining into adhesive and supportive structue for implantation
25
Q

What is follicular atresia?

A
  • Apoptosis of ovarian follicle ( granulosa cells and oocytes) that can occur during any time in development
    • Thecal cells persist and repopulate the cellular stroma of the ovary
      • Thecal cells keep LH receptors and ability to produce androgens, called interstitial gland of ovary
26
Q

How is GnRh released? Describe it in the early and late follicular phase.

A
  • pulsatile from the hypothalamus
  • in early follicular phse gonadotrophs arent sensitive, each burst gives slight rise in LH
  • Later in follicular phase gonandotrophs in ant pit become very sensitive to GnRH in portal blood and it triggers a larger relase of LH
27
Q

Where do inhibins come from and what do they do

A
  • FSH stimulates granulosa cells to produce inhibins before ovulation
  • Inhibins will inhibit FSH production in a negative feedback manner
28
Q

Before ovulation what do LH and FSH act on?

A

cells of the developing follicle:

  • Theca cells-LH
  • Granulosa cells LH and FSH
29
Q

After ovulation what does LH act on?

A

Corpus luteum cells

30
Q

where are activins produced and what do they do?

A

Granulosa cells same as inhibins, but activins will stimulate FSH releases from the pituitary

31
Q

For most of the menstrual cycle estrogens and progestin exert negative feedback on HPA, but what is unique about the difference in estrogen and progestin in this NFB cycle?

A
  • Estrogens exert negative feeback at low and high concentrations and progestinns are effective only at high cocentrations
32
Q

Describe positive feedback in he follicular phase.

A
  • Estradiol levels rise gradually during first half of follicular phase and then steeply during second half
  • After they reach certain threshold HP axis reverses it sensitivity to estrogens and exerts a PFB
    • This promotes the LH surge
33
Q

During the late luteal phase, what leads to decreases in levels of progesterone, estradiol, and inhibin?

A

Demise of the corpus luteum

34
Q

After onset of menstruation what happens with GnRH?

A

The HP axis returns to follicular phase patteron of LH secretion resulti in a gradual increase in GnRH pulses

35
Q

High levels of __ during pre ovulatory follicular phae of menstrual cycle lowers BBT.

A

Estrogen

36
Q

Higher levels of _____ released by the ___ after ovulation raises BBT. If pregnancy doesn’t occur this structure disintegrates andc causes a drop in BBT coinciding with the next menstruation.

A

Progesterone and CL

37
Q

What phase does the follicle synthesize estrogen?

A

Follicular phase

38
Q

What phase does the corpus luteum synthesize estrogen?

A

Luteal phase

39
Q

In the endometrial cycle what is the menstrual phase?

A
  • If pregnancy didn’t occur, estrogen and progesterone secretions from CL decrease and it regresses
  • The endometrium degenerates and tissue breaks down resulting in menstrual bleeding
    • Day one of the cycle
40
Q

Describe the proliferative phase of the endometrial cycle.

A
  • Occurs on day 5
  • Proliferation of basal stromal cells in zona basalis and epithelial cells
  • Stroma will give rise to CT components of endometrium
  • Proliferation and differentiation of endometrium are stimulated by estrogen
    • levels of estrogen rise early in the follicular phase and peak before ovulation
41
Q

Describe the secretory phase of the endometrial cycle.

A
  • Final phase of uerine cycle corresponds to luteal phase of ovarian cycle
  • Middle to late phase:
    • vascularization endometrium increases along with glycogen content
    • Progesterone promotes differentiation of stromal cells into predecidual cells
42
Q

Describe menopause.

A

12 months after last menstrual period marks loss of ovarian reserve

  • occurs usually around 51 yrs of age
  • due to reduction in estrogen and low levels of inhibin
  • NO NFB of LH and FSH so high LH and FSH levels
43
Q

Menopause sx

A

​In months or years leading up to menopause symptoms are:

  • irregular periods
  • vaginal dryness
  • hot flashes
  • night sweats
  • mood changes
  • weight gain slow metabolism
  • thinning hair and dry skin
  • loss of breast fullness

GIGU Final (12 decks)

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