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When does oogenesis take place?
- before birth - in the ovaries of the fetus
- arrested at prophase I of meisosis
What causes frozen prophase I oocytes to finish meiosis?
- After puberty, hormonal changes stimulate the first division and ovulation. This yields a polar body and a large secondary oocyte.
- second meitoic division only occurs when the oocyte has been fertilized by sperm which also produces a polar body.
Do sperm and egg nuclei fuse immediately?
No, seconday oocyte has to complete meiosis to become the ovum
What cells produce testosterone and what hormone are they stimulated by?
What cells are stimulated by FSH in the female reproductive system?
FSH stimulation begins at puberty.
Granulosa cells to secrete the zona pellucida around the egg to protect it.
Where do sperm mature?
Epidydimis - this is called spermatogenisis - usually gain motility
What cells make and secrete estrogen?
What structure secretes progesterone?
- Corpus leuteum
- Placenta if pregancy takes place
What is ectopic pregnancy?
When implantation occurs in the fallopian tubes
What happens at the LH surge?
What hormone maintaines the endometrial lining?
Progesterone. This lining is important in pregnancy. If no progesterone is made, miscarrages are very likely.
3 phases of the overian cycle
- Follicular phase: primary follicle matures and secretes estrogen
- Ovulatory phase: secondary oocyte is released from the ovary. Triggered by LH surge
- Luteal phase: formation of the corpus luteum which secretes both progesterone and estrogen
What is GnRH, LH, FSH inhibitd by?
Negatively by estrogen, especially after ovulation when the corpus luteum contributes to feedback inhibition
What would happen if a woman was on the pill for prolonged periods of time?
- No menstruation
- Prevention of ovulation because LH and FSH would be inhibited (no LH surge)
Why does the corpus leuteum degenerate?
- Due to decreased levels of LH which keeps it alive
- LH reduced due to feedback by estrogen and progesterone
- This ensures that ovulation does not occur during pregnancy - this is also why estrogen and progesterone are high during pregnancy
What hormone does the zygote release?
- hCG (human chorionic gonadotropin)
- hCG take the place of LH in maintaining the corpus leuteum, which in turn maintains estrogen and progesterone production, and as a result, LH is not necessary b/c it is feedbacked
HCG in the mother's urine is the first sign of pregnancy.
Once the placenta is formed, it takes over HCGs actions.
When does meiosis I and II occur in oocytes?
- Meiosis I - prior to ovulation (before birth) --Primary oocyte
- (secondary oocyte upon ovulation)
- Meiosis II - after fertilization -- Ovum
*Fertilization happens only AFTER the Ovum forms
Fast and slow blocks of polyspermy
- Fast: depolarization due to influx of sodium
- Slow: Ca influx (caused by depol) = cortical reaction which hardens the zona pellucida and increasing metabolism and protein synthesis
Does cleavage increase the size of the initial embryo?
Embryonic development stages
- morula: initial repetative mitotic divisions of teh zygote
- blastula: which has the tropoblast (plancenta) and inner cell mass (embryo) - lodges in the uterus and is comprised of embryonic stem cells
- gastrulation: designation of 3 primary germ layers
- neurula: notochord induces ectodermal tissue
What happens if corpus luteum is removed during the first trimester?
- Menstruation will occur resulting in a miscarriage
- This is either because (1) progesterone levels are not maintained (2) LH levels are decreased which they should but (3) hCG not produced which maintains the corpus luteum.
When does the placenta take over in making progesterone?
- After the first trimester when it is developed
- this allows hCG release to be halted and corpus leuteum to be degenerated
- remember, estrogen and progesteroe levels are still high so LH and FSH are low so ovarian cycle does not continue
Ectoderm, Mesoderm, Endodermal tissue derivatives
- Ectoderm: nervous system, skin, pituitary gland, cornea, lens, nasal, oral, anal epithelium
- Mesoderm: all muscle, bone, and connective tissue (including blood), cardiovascular and lymphatic system, kidneys, ureters, gonads, reproductive ducts
- Endoderm: GI tract and epithelia, GI glands (liver, pancrease, gallbladder, etc), respiratory epithelium, bladder, epithelial lining of urogenital organs
What NS division is responsible for ejaculation and erection?
- "Point and Shoot"
- Erection - para
- Ejaculation - sympa
Do spermatoGONia devide by mitosis or meiosis?
What actions does testosterone have?
Stimulates germ cells to become sperm and promotes male secondary sex characteristics, closing of epiphyseal plates
LH causes ________ cells to secrete __________
Leydig cells ; testosterone
FSH stimulates __________
Sertoli Cells to nurture spermatocytes and spermatids
Where does the production of sperm occur?
The seminiferous tubules
Path of sperm maturation
Spermatagonia --> spermatocytes --> spermatids --> spermatozoa
The spermatozoan requires_______to carry forth its actions
Energy and thus mitochondria in its mid portion to power the tail, allowing it to swim to the egg
Path of sperm ejaculation
Seminiferous tubules (secretion) --> epididymus (maturation) --> vas deferens --> urethra
What is semen composed of?
Fluid from the seminal vesicles, prostate, and bulbourethral/Cowper's glands
Where do sperm become activated for fertilization?
What does LH secretion promote in the female reproductive system?
Theca cells are stimulated to secrete estrogen
How does the relationship between estrogen and LH vary?
Normally estrogen negatively feedbacks on LH.
But during ovulation...rapidly raising estradiol levels actually cause a surge in LH levels <-- luteal surge, thereby inducing a positive feedback effect.
What is the end product of the luteal surge? 2.
- 1. A burst follicle ----> corpus luteum
- 2. A secondary oocyte
What is the role of the corpus luteum and what happens to it?
It is the bust follicle without the oocyte.
The corpus luteum secretes estrogen and progesterone throughout pregnancy...if the female is NOT preggers, the corpus luteum degrades into the corpus albicans.
Where does fertilization normally take place?
In the fallopian tube