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When does oogenesis take place?
- before birth
- arrested at prophase I of meisosis
- 2 million at peak, born with around 400,000, only 400 released
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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.
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Do sperm and egg nuclei fuse immediately?
No, oocyte has to complete meiosis
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What cells produce testosterone and what hormone are they stimulated by?
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What cells are stimulated by FSH?
Sustenacular/Sertoli - promote spergatogenisis
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Where do sperm mature?
Epidydimis - this is called spermiogenisis - usually gain motility
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What cells make and secrete estrogen?
Granulosa cells
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What structure secretes progesterone?
- Corpus leuteum
- Placenta if pregancy takes place
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What is ectopic pregnancy?
When implantation occurs in the fallopian tubes
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What happens at the LH surge?
Ovulation
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What hormone maintaines the endometrial lining?
Progesterone. This lining is important in pregnancy. If no progesterone is made, miscarrages are very likely.
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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
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At what phase is the endometrium when ovulation occurs?
Proliferative
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What is GnRH, LH, FSH inhibitd by?
Negatively by estrogen, especially after ovulation when the corpus luteum contributes to feedback inhibition
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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)
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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
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Where is the chorion derived from?
The zygote
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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
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When does meiosis I and II occur in oocytes?
- Meiosis I - prior to ovulation (before birth)
- Meiosis II - after fertilization
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Where does sperm bind to?
Bindin receptors via bindin which is found on the acrosomal process
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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
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Does cleavage increase the size of the initial embryo?
Nope
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Embryonic development stages
- morula:
- blastula: which has the tropoblast (plancenta) and inner cell mass (embryo)
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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.
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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
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Ectoderm, Mesoderm, Endodermal tissue derivatives
- Endoderm: 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
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Secretions of
Seminal vesicles
Prostage gland
Bulbourethral glands
Testes
- Seminal vesicles: fructose (nourishment and energy)
- Prostage gland: fructose and coagulant
- Bulbourethral glands: alkaline (neutralize acid in vagina and urethra)
- Testes: sperm
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What NS division is responsible for ejaculation and erection?
- "Point and Shoot"
- Erection - para
- Ejaculation - sympa
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Do spermatoGONia devide by mitosis or meiosis?
Mitosis
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What hormone directly stimulats division of spermatogonia?
Testosterone
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LH causes ________ cells to secrete __________
Interstitial, testosterone
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FSH stimulates __________
sustenacular/sertoli cells
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Which male hormone inhibits FSH release?
inhibin which is produced by the sustenacular cells
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Mullerian or Wolfian development by default?
- Mullerian resulting in female genitalia
- Y chromosome leads to the development of testes which causes male internal and external genetialia to develop by producing testosterone and mullerian inhibiting factor
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