Weeks 1-2 of Human Development S1M1

  1. Sperms have what stages of development in order
    • Spermatogonia 2n
    • Spermatocye (Primary 4n and Secondary 2n)
    • Spermatogenesis 1n
    • - Spermatid
    • - Spermatazoa (motile)
  2. When do primary oocytes start meiosis
    By the seventh month of development
  3. Primary oocytes are arrested in what phase of meiosis 1
  4. Usual site of fertilization of the oocyte is in the
    Ampullary region of Fallopian tube (1/3 outer part)
  5. Viability of gametes last for how long after their release
    Oocytes (24 hrs), Sperm ( 48 hrs)
  6. What oocyte is released at ovulation
    Secondary Oocyte in 2nd meiotic division
  7. How many sperms reach secondary oocyte in ampullary region of fallopian tube
    About 300 to 500
  8. Spermatozoa can’t fertilize oocyte unless they undergo
    Capacitation and acrosome reaction
  9. What layers do the sperm have to penetrate before reaching the ovum
    • Corona radiata
    • Zona Pellucida

    "After a corona your in the zone"
  10. What happens once the sperm penetrates the oocyte plasma membrane
    There is a fast block, and a slow block preventing other sperm from entering
  11. When does meiosis II start in the secondary oocyte
    After the sperm enters
  12. Nucleus of ovum and sperm after penetration is called
    • Female Pronucleus
    • Male Pronucleus
  13. When is fertilization finished and in turn the zygote made
    When the male pronucleus and female pronucleus fuse
  14. After the 3rd cleavage, the compacted ball of cells are held together by
    Tight junctions
  15. During cleavage the compact cells don't grow because
    They are held together by Zona pellucidaImage Upload 1
  16. At about 3 days, the zygote is a ball of cells called the
    Morula (about 12-16 cells)
  17. As cleavage continues, the morula does what
    Passes down the uterine tube towards the uterus.
  18. About day 4, the embryo does what
    Enters the uterine cavity, the zygote is divided into 2 parts, an outer cell mass called the trophoblast and inner cavity called a blastocyst cavityImage Upload 2
  19. The trophoblast gives rise to
    Part of the placenta and the embryoblast (inner cell mass)Image Upload 3
  20. The entire zygote is called the
    • Blastocyst
    • Image Upload 4

  21. When does the zona pallucida dissappear
    While the blastocyst sits in the uterine cavity for about two days
  22. On about day 6, the trophoblast (outer shell)
    Becomes sticky by L-selectins, and attaches to the uterine epithelium and works its way in
  23. Following the L-selectins attaching to the uterine, integrins of trophoblast bind to
    Laminins of epithelium causing attachment to fibronectin for migration to occur
  24. By end of 1st week of development
    The blastocyst is superficially implanted
  25. Embryoblast is
    The cell mass in the blastocyst
  26. During the second week of development the embryoblast and the trophoblast
    Grow at different rates
  27. What happens to the embryoblast at days 7 and 8
    It seperates into two layers the epiblast (columnar) and hypoblast (cuboidal)Image Upload 5
  28. The hypoblast and epiblast layers form the
    Bilaminar germ disc, this will form the tissues of the embryo
  29. Days seven and eight the trophoblast divide into what two layers
    • CYTOTROPHOBLASTImage Upload 6
  30. The amnion is, and develops where and when
    A protective membrane that develops in the epiblast and is eventually surrounds the entire embryo, starts development on the 8th day
  31. When is the embryo completely embedded in the endometrium and have the fibrin plug
    Days 9-10
  32. What portion of the newly formed embryo is attached to the maternal endometrial stroma
    SyncytiotrophoblastImage Upload 7
  33. Where and when does the maternal blood flow in
    • Lacunar spaces in the syncytiotrophoblast (Day 28)
    • Can be mistaken for a period and can interfere with an pregnancy dating
  34. The extraembryonic mesoderm is found where
    • Covering over the secondary yolk sac and amnion
    • Lines the inside of the cytotrophoblast
    • Inner layer of the chorionic cavity
    • Space between the cytotrophoblast and the primative yolk sac
  35. The only place where the extraembryonic mesoderm traverses the chorionic cavity is in the
    Connecting stalk
  36. The connecting stalk becomes the
    Umbilical cordImage Upload 8
  37. The prechordal plate is a
    "uniquely thickened portion" of the endoderm that is in contact with ectoderm (cranial development occurs here)
  38. Placenta praevia
    is an complication in which the placenta is attached to the uterine wall close to or covering the cervix
  39. An ectopic pregnancy, is a complication of pregnancy in which
    The pregnancy implants outside the uterine cavity
  40. What is the main enzyme used to break down the corona radiata for the sperm to enter
  41. Why doesn't the mothers body detect the foreign sperm and chromosome and destroy it
    Major Histocompatibility complex class 1B molecule (HLA-G). This blocks recognition of conceptus as foreign tissue
  42. Heusers membrane
    Forms the lining of the primitive yolk sac (days 9-10)
  43. By day 12 the hypoblast
    Begin to grow over the inside of the Heusers membrane
Card Set
Weeks 1-2 of Human Development S1M1