Embryology Midterm

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Palmer2012
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182492
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Embryology Midterm
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2012-11-08 12:32:39
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Embryology Midterm
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Embryology Midterm
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  1. difference in ovary and testes development
    • similar untill 4th week of development 
    • testes are directed by Sry gene, testosterone and Mullerian-Inhibiting Factor
    • ovaries have no factor involved
  2. why haploid?
    • allows for random assortment of maternal and paternal chromosomes between gametes
    • relocates segments by crossingover, shuffles genes 
  3. spermatogenesis
    begins at puberty, including all of the events by which spermatogonia are transformed into spermatozoa.  regulated by Luteinizing Hormone (LH) and Follicle stimulating Hormone (FSH)
  4. oogenesis 
    maturation of oocytes begins befor birth.  the oogonia enter meiosi 1 to form primary oocytes. during puberty the primary oocyte completes mieosis 1 and forms the secondary oocyte and remains in meiosis 2 and is ovulated.  fertilization occurs and meiosis 2 is complete forms mature oocyte
  5. primary oocyte
    • diploid
    • arrested in meiosis 1 untill puberty
  6. primary follicle ( secondary oocyte)
    • occurs during puberty 
    • meiosis 1 completes nd enters meiosis 2 untill ovulations
  7. secondary follicle
    • occurs at fertilization 
    • meiosis 2 completes and forms mature oocyte, become haploid
  8. promordial follicles
    contain immature oocytes currounded by a single layer of support cells 
  9. primary follicles 
    the support cells change structure the oocyte genome is activated and genes become transcribed 
  10. secondary follicles
    fully grown oocyte surrounded by a zone pellucida
  11. Role of the FSH in the menstral cycle
    FSH stimulates the development of ovarian follicles and the production of estrogen by its follicular cells. it also stimulates the synthesis of LH receptors
  12. role of LH in the menstral cycle
    • LH causes the oocyte t complete meiosis 1, initiating meiosis 2. 
    • also stimulates the production of progesterone by follicular stromal cells and causes follicular rupture and ovulation
  13. when does the primary oocyte form
    before ovulation phase in the follicular phase of ovarian cycle
  14. what cell secretes estrogen?
    follicular cells 
  15. what cells secrete progesterone?
    the corpus luteum
  16. when does ovulation happen?
    during ovulatory phase which is around day 14-15 of the sendometrial cycle
  17. what happens if the oocyte fails to be fertilized?
    corpus luteum dies levels of progesterone drop suddenly.  and shedding of the endometrial lining
  18. when does meiosis 1 start?
    before birth
  19. when does mieosis 1 finish?
    at puberty and occurs during ovulatory phase
  20. when does mieosis 2 start?
    at puberty when the oocyte finishes meiosis 1 stays untill fertilization.
  21. what are consequences if a pregnancy does not occur?
    endometrial linning undergoes ischemia. the upper region of the endometrial stroma contains numerous decidual cells.  spiral arteries constrict causeing ischemia resulting in shedding of endometrial lining.
  22. what changes when oocyte is fertilized
    lining of uterus undergoes the decidual reaction, endometrial glands proliferate and the endometrial vascularity increases.  the blastocsyt losses the zone pellucida and becomes adherent and embeds into the uterine lining.  corpus luteum enlarges and become corpus luteum of pregnancy.
  23. common site of fertilization
    the ampulla region of the oviduct
  24. what will happen to the oocyte immediatly after fertilization?
    zona pellucida undergoes lysis.  become impermeable to other sperm
  25. what is the term ovum?
    haploid female reproductive cell or gamete
  26. what is term zygote
    initial cell formed when 2 gamete cells are joined by means of sexual reproduction.  earliest stage in embryo development
  27. what modification does a sperm have to go through before it fertilizes the oocyte?
    has to pass through the corona radiata. by releasing hyaluronidase from the sperm acrosome, tubal mucosal enzymes and flagella action
  28. what is the acrosomal reaction?
    the acrosomal enzymes causes lysis of the zona pellucida
  29. acrosomal enzymes
    • esterases
    • acrosin
    • neuraminidase
  30. how many layers does sperm have to go through to fertilize the oocyte?
    about 5
  31. what is the reaction of the zona pellucida if sperm penetrates is?
    undergoes lysis and become impermeable to other sperm
  32. what is cleavage?
    a series of miotic divisions that occur in the zygote
  33. what is the morula?
    the 12-32 stage of division, the blastomeres form a morula which consists of an inner and outer cell mass.  occurs aound 3rd day after fertilization looksl ike a mulberry
  34. what is the blastocyte
    occurs day 4 forms when fluid secreted within the morila forms the blastocyte cavity.  this seperates the inner cell mass from the outer cell layer
  35. what are consequences of the oocyte if fertilization happens ?
    M2 finishes for the oocyte resulting in the formation of the diploid number of chromosomes (46).  maternal and paternal chromosomes intermingle and sex is decided at this time

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