L23 - Female reproductive cycle Flashcards
List all the phases in prophase of meiosis?
–Preleptotene: DNA synthesis
–Leptotene: size increases; chromosomes visible
–Zygotene: pairing of chromosome at some points
–Pachytene: pairing along the entire chromosomes, shortening and thickening of chromosome; crossing over.
–Diplotene: formation of chiasmata(site of crossing over).
- DICTYOTENE
–Diakinesis: shortening and thickening of chromosome
Primary oocytes arrest at which phase of Prophase I?
Dictyotene
before Diakinesis
Compare the separation of genetic material in Meiosis I and II?
–Meiosis I: separation of homologous chromosome
–Meiosis II: separation of sister chromatids
Define the 2 interruptions in the meiosis cycle of oocyte?
1st = At Prophase I (after dictyotene) until puberty
2nd = After metaphase II until fertilization
Define the number of oogonia formed in utero?
Increase to 7 million oogonia by 6 months (mitosis)
Degenerate to 1 million primary oocyte by birth
400 ovulated in life
5 MATURATION states** not folliculogenesis** of ovarian follicles?
Primordial follicle
> > developing follicle
> > mature follicle
> > ovulated follicle
> > corpus luteum
2 functions of ovarian follicles?
- Reproduction: house the oocyte
* Endocrine: follicular cells respond to gonadotropins and sex hormones at different stages
Define the phases of folliculogenesis?
1) Follicular phase
2) Preantral phase
3) Antral phase
4) Preovulatory phase
5) Ovulation
6) Luteal phase
Describe the follicle maturation processes in follicular phase? think selection
High GnRH = high FSH/LH release at pituitary»_space; FSH increase follicle growth
- Recruitment: Cohort of prenatral follicles from resting pool grow (recruitment)
- Selection: only 1 follicle develop into preovulatory follicle:
Highest number of FSH receptor chosen
Describe the change in primary oocyte size in Preantral phase?
Primordial follicle: <50μm
|»_space;> Primary follicle: 50-100μm
The preantral phase of folliculogenesis is gonadotrophin dependent. T or F?
False
not dependent
Able to respond to gonadotrophin at the end of Preantral phase
Describe the changes in the ovarian follicle during preantral phase?
- Proliferation of follicular cells:
a) Develop Zona Pellucida
b) Develop Granulosa cells: express Estrogen and FSH receptor
c) Develop Theca cell: express LH receptors
Role of granulosa cells in follicles?
Finger-like projections penetrate zona pellucida: allow external gonadotropin signal to go through to oocyte
> > regulate meiosis of oocyte
Describe the changes to ovarian follicle during antral phase of folliculogenesis?
Increase in size to 100-1000 μm
Secondary follicle formed:
Gonadotrophin dependent»_space; Proliferation of follicular cells:
- Formation of Antrum and Cumulus
- Form Theca interna and externa
- High FSH and Estrogen increase LH receptor expression at follicular cells
Explain the 2 cell theory of estrogen production? at thecal and granulosa cells
1) LH binds to LH receptor on thecal cells»_space; convert cholesterol to androstenedione (androgen)»_space; circulation or diffuse across basement membrane to granulosa cells
2) FSH binds to FSH-R on granulosa cells»_space; stimulate aromatase to convert Androstenedione to estrogen»_space; into circulation or follicular fluid
Explain how Antral phase follicular development is accelerated?
Estrogen simulate granulosa cells to increase cell division and express more estrogen receptors
» More estrogen made
» Positive feedback
Describe the changes to follicle in the preovulatory phase of folliculogenesis?
Tertiary follicle formed: >1000μm
- Increase size of antrum, stigma
- Cumulus cells surround follicle > form corona radiata
- LH surge completes meiosis-I , arrest at Metaphase II»_space; secondary oocyte
- Granulosa cells make low levels of Progesterone
Describe the changes to ovarian follicle at ovulation? mechanisms to cause ovulation
Rupture follicle membran:
a) Increase production of follicular fluid»_space; increase pressure in antrum
b) Produce Prostaglandin and proteolytic enzyme to dissolve follicular wall
c) Oxytocin contract follicular membrane
> > > Secondary oocyte and cumulus oophorus ovulated
Describe changes to ovarian follicles at luteal phase?
Vascularization of the granulosa layer
Lutenization: Granulosa cell Hypertrophy + transform = Corpus luteum (80% granulosa cells + 20% thecal cells)
> > Production of estrogen, progesterone
Compare the fate of the corpus luteum with or without fertilization?
Fertilization = Embryo blastocyst + placenta secrete hCG (LH-like) = maintain corpus luteum lifespan for 3 mon.
No fertilization: Luteolysis (degeneration) > corpus albicans
List the hormones secreted by pituitary, hypothalamus and ovaries in female reporductive cycle?
Hypothalamus = GnRH Pituitary = FSH, LH Ovary = estradiol, progesterone (feedback to hypothalamus)
Summarize the role of estrogen from dominant follicle?
- Primes endometrial response to progesterone
- Primes GnRH action on LH secretion for LH surge
- Enhances transport of ovum in oviduct
- Enhances sperm transport through cervical mucus
- Inhibits growth of cohort follicle
Summarize the hormonal interaction during the follicular phase of folliculogenesis/ before ovulation? exam
GnRH stimulate synthesis and release of FSH and LH
> > FSH stimulate follicular development: Thecal, granulosa cells make Estrogen/Estradiol
> > Estrogen NEGATIVE feedback to pituitary and hypothalamus for GnRH and FSH, LH RELEASE
> > but stimulate pituitary for FSH, LH SYNTHESIS (store)
Summarize the hormonal interaction during the Ovulation phase of folliculogenesis? exam
High estrogen for 2-3 days switches negative feedback to Positive feedback*****
- Estrogen increase synthesis and RELEASE of FSH, LH
> > Cause FSH, LH surge
> > cause lutenization and form corpus luteum
> > Corpus luteum makes LOW progesterone and estrogen to positively increase GnRH release + Pituitary sensitivity
> > More FSH, LH released
Summarize the hormonal interaction during the Luteal phase of folliculogenesis? exam
Switch from positive feedback to negative feedback:
- HIGH estrogen and progesterone from corpus luteum decrease GnRH release
- High progesterone block estrogen» block synthesis and secretion of FSH, LH
Summarize the hormonal interaction during the end of Luteal phase of folliculogenesis without fertilization??
Corpus luteum luteolysis
> > decrease estrogen and progesterone release
> > Remove inhibition on GnRH
> > cycle restart
3 functions of progesterone from corpus luteum?
Control Ovulation
Uterine secretion in preparation for implantation of the embryos
Development of the embryo
Describe changes to cervical mucus in female sex cycle?
Before ovulation: Increase cervical mucus ‘ferning’ = decrease viscosity
After ovulation = no ferning = more viscous
Changes in basal temperature during female sex cycle?
Decrease up to ovulation
Huge increase and plateau after ovulation
2 phases of endometrium growth during female sex cycle?
Proliferative = follicular phase of ovarian cycle
Secretory = Luteal phase
List 5 ways to detect ovulation?
Menstrual cycles–regular cycles
Basal body temperature
Urinary LH level
Blood-progesterone levels
Ultrasound
