Reproductive Systems

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Reproductive Systems
2012-06-16 17:00:46

MCAT Biology
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  1. When does oogenesis take place?
    • before birth - in the ovaries of the fetus 
    • arrested at prophase I of meisosis
  2. 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.
  3. Do sperm and egg nuclei fuse immediately?
    No, seconday oocyte has to complete meiosis to become the ovum
  4. What cells produce testosterone and what hormone are they stimulated by?
    • Leygdig Cells
    • LH
  5. 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. 
  6. Where do sperm mature?
    Epidydimis - this is called spermatogenisis - usually gain motility
  7. What cells make and secrete estrogen?
    Granulosa cells
  8. What structure secretes progesterone?
    • Corpus leuteum
    • Placenta if pregancy takes place
  9. What is ectopic pregnancy?
    When implantation occurs in the fallopian tubes
  10. What happens at the LH surge?
  11. What hormone maintaines the endometrial lining?
    Progesterone. This lining is important in pregnancy. If no progesterone is made, miscarrages are very likely.
  12. 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
  13. What is GnRH, LH, FSH inhibitd by?
    Negatively by estrogen, especially after ovulation when the corpus luteum contributes to feedback inhibition
  14. 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)
  15. 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
  16. 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.
  17. 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  
  18. 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
  19. Does cleavage increase the size of the initial embryo?
  20. 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 
  21. 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.
  22. 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
  23. 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
  24. What NS division is responsible for ejaculation and erection?
    • "Point and Shoot"
    • Erection - para
    • Ejaculation - sympa
  25. Do spermatoGONia devide by mitosis or meiosis?
  26. What actions does testosterone have? 
    Stimulates germ cells to become sperm and promotes male secondary sex characteristics, closing of epiphyseal plates 
  27. LH causes ________ cells to secrete __________
    Leydig cells ; testosterone
  28. FSH stimulates __________
    Sertoli Cells to nurture spermatocytes and spermatids 
  29. Where does the production of sperm occur?
    The seminiferous tubules
  30. Path of sperm maturation
    Spermatagonia --> spermatocytes --> spermatids --> spermatozoa
  31. 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
  32. Path of sperm ejaculation 
    Seminiferous tubules (secretion) --> epididymus (maturation) --> vas deferens --> urethra 
  33. What is semen composed of?
    Fluid from the seminal vesicles, prostate, and bulbourethral/Cowper's glands 
  34. Where do sperm become activated for fertilization?
    The vagina
  35. What does LH secretion promote in the female reproductive system?
    Theca cells are stimulated to secrete estrogen
  36. 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.  
  37. What is the end product of the luteal surge? 2. 
    • 1. A burst follicle ----> corpus luteum 
    • 2. A secondary oocyte  
  38. 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.  
  39. Where does fertilization normally take place?
    In the fallopian tube