Flashcards in Female Reproduction Deck (41):
Describe the germ cell development
-Mitosis of oogonia
-1st meiotic division to form several million oocytes
How many oocytes are present during puberty?
Typically there are about 400-500 ovulations over a lifetime until menopause
Where are the receptors located?
How is estrogen regulated?
Theca cells produce estrogens which inhibit the secretion of GnRH, LH and FSH
What is the difference between inhibin A and inhibin B?
Inhibin A produced by dominant follicle and corpus luteum
Inhibin B produced by small follicles
What are the three phases of the follicular wave?
Recruitment: small antral follicles are recruited from the ovarian pool and produce small amounts of E2
Selection: follicles are selected from previously recruited small follicles and either become atretic or develop further.
Dominance: selected follicles that do not become atretic become dominant follicles that produce large quantities of E2
Is it common to have more than one follicular wave during the follicular phase?
Yes, more than one follicular wave typically occurs during the follicular phase of the reproductive cycle
minor waves do not result in ovulation
What are the levels of FSH and LH during the follicular wave?
Recruitment: high FSH, low LH, no inhibin, no estradiol
Selection: low FSH, moderate LH, low inhibin
Dominance: low FSH, high LH, high inhibin
What is atresia?
Degeneration of follicles
How is ovulation brought about?
- Elevated blood flow
- Breakdown of connective tissues
- Ovarian contractions
What is the effect of a preovulatory LH surge?
- Increase PGF2a: increase contraction and release lysosomal enzymes
- Increase blood flow to ovary and dominant follicle: leads to edema which increases follicular pressure
What is the importance of the gap junction breakdown?
Gap junction breakdown between granulosal cells and oocytes will initiate the removal of meiotic inhibition leading to the first polar body initiating haploid oocytes which will lead to fertilization
What does the theca interna and granulosa cell form after ovulation?
What does the tonic centre produce?
Low levels of GnRH to maintain basal levels of LH to stimulate the corpur luteum to secrete P4
What is the function of P4?
- Promote alveolar development
- inhibits the myometrium and reduce its contractility and tone ("blocks" pregnancy)
- Negatively feedbacks on GnRH neurons: GnRH, LH, FSH productions are suppressed
What happens if fertilization doesnt occur?
If fertilization doesnt occur then the corpus luteum undergoes luteolysis and a new reproductive cycle is initiated
What is HcG used for?
hCG stimulates corpus luteum to maintain steroids until feto-placental unit takes over basis of home pregnancy
Describe the changes that occur during the menstrual cycle
Ovarian changes: follicle growth and maturation, corpus luteum formed and functioning, luteolysis
Uterine changes: menstruation, proliferative phase, secretory phase, pre-decidual phase
Vaginal changes: high pH watery mucus conducive to sperm survival, low pH viscous mucus inimical to sperm survival
Where does fertilization occur?
Fertilization of the ovum occurs in the oviduct
Hydrolytic enzymes in the acrosome loosen the corona radiata cells around the ovum, one sperm penetrates and fertilizes the oocyte
Ciliated cells move the ovum along the oviduct to the uterus
Describe the changes in the uterine endometrium during the menstrual cycle
Day 1 - 3: breakdown
Day 3 - 14: estrogenic proliferative phase
Day 14 - 28: progestattional secretory phase
How do IUDs work?
IUDs are molded plastic devices which disrupt the normal uterine environment, by slowly releasing snthetic P4
How does Plan B work?
Plan B uses synthetic progesterone and should be taken <72 hours after unplanned intercourse or suspected contraceptive failure
high levels of P4 can inhibit ovulation or ovum/sperm transport and implantation to reduce the risk of unplanned pregnancy
At what weight are plan B pills less effective and not effective?
- Less effective: 165 - 176lbs (75 -80kh)
- Not effective: >176lbs (>80kg)
Explain how RU486 induces abortion
- RU486 is an anti-progesterone
- promote decidual breakdown leading to detachment of the blastocyst
- decrease in secretino of hCG, there will also be a decrease in progesterone in the CL
- there is accumulation of prostaglandins and enhances uterine sensitivity to prostaglandin disturbing the balance between prostaglandin and progesterone increasing uterine contractility
- there will be cervical softening, which faciltates expulsion of the blastocyst
When does X silencing occur?
Later in development, about 32 cell stage and it is random (Xp or Xm)
Talk about the fetalplacental endocrine unit
-After implantation the blastocyst develops into a trophoblasts, it secretes hCG
-hCG maintains steroid production by the corpus luteum and suppresses LH and FSH and restart of the menstrual cycle
- at 9 weeks, the placental unit produces pregnenolone that is converted to progesterone
- corpus luteus gradually disappears
- output of progesterone and estrogens by the fetoplacental unit continuously increases during pregnancy
What are some of the changes in the breast during pregnancy?
- changes start two years before end of puberty
- estrogens stimulate duct formation and accumulation of fat
- estrogen affects the breasts during pregnancy
- glucocorticoids, PRL and placental lactogen induce enzymes necessary for milk production
- high conc of estrogen and progesterone prevent milk production
- after parturition estrogen and progesterone levels fall, but PRL stays high
How does the mother's body adapt to pregnancy?
-considered a successful parasite, the fetal placental unit manipulates the maternal host
What happens during parturition?
Placenta produces increasing levels of CRH from week 28 to delivery
Stimulates SCTH from fetus to increase fetal cortisol and CRH which may have direct effects on PGF and oxytocin actions
EStrogen is a stimulant and increase contraction of myometrial layers
How long does it take maternal steroid levels to return to normal?
1 - 3 days
the pituitary gland will increase in size by about 1/3 during pregnancy and does not decrease until the end of lactation
after lactation (>3 months), normal cycles resume in about 17 weeks
When does menopause typically occur?
age 51 for 90% of women
How does menopause start /occur?
Waves of recruitment and atresia starting in utero eventually reduces oocyte pool to about 25,000 then rate of follicular atresia increases
Why do people use hormone replacement therapy?
To treat these symptoms including vasometer, osteoporosis, short term memory changes, depression with estrogen
What are some examples of hormone replacement therapy?
- progesterone promotes conversion of estradiol to estrone in the target cell, estrone has a lower affinity to estrogen receptors and may dimish cancer risk
- long term effects are unknown but bone loss is about 1 -2% per year
What are disturbances of the menstrual cycle can occur?
- Primary amenorrhea: genetic defects in gonadal maturation or estrogen synthesis, depletion of follicles
- Secondary amenorrhea (failure to ovulate in a six month period): excessive androgen production ,pituitary disease, psychiatric disturbances, nutrition
Why does ovulation fail (menstrual cycle without ovulation) sometimes?
- Lack of positive feedback of estrogens
- Lack of pulsatility of GnRH release
- Lack of ovulation leads to irregular length of period
How can you detect ovulation?
- Based on progesterone surge
- rise in the basal body temperature in the middle of the cycle
- increase of endometrial mucosa secretion
- increase in plasma progesterone or excretion of metabolites of progesterone
Decribe the process of artificial induction of ovulation
- blocking of estrogen receptors in the hypothalamus, this prevent negative feedback by estrogens and increases LH and FSH
- injection of LH, FSH and hCG
- injection of GnRH in a pulsatile fashion
Describe the process of IVF
- fertilization of ovum and implantation in the uterus after first cleavage is observed
- blocks ovarian function creating an artificial corpus luteum
- super ovulate ovary to have more than one follicle and induce multiple ovulations
- 60% success rate for pregnancy
What are the main factors of infertility?
- Age plays a large role, about 20% of NA women have their first child after 35: age dependent loss of follicles
- spontaneous abort rates also increase with age