Human Development 1

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  1. Gametogenesis
    • formation of gametes
    • - either spermatozoa or ova
    • - haploid (1N)
  2. Spermatogenesis
    • Male gametogenesis
    • occurs in seminiferous tubules (74 days)
    • starts at puberty, ends at death
  3. steps in spermatogenesis
    Spermatogonium (2N) --> Primary Spermatocyte (4N) --> 2 Secondary Spermatocytes (2N) --> 4 Spermatids (1N) --> 4 Spermatozoans (1N)
  4. Spermatozoan
    • male gamete
    • head contains nucleus and acrosomes
    • midpiece contains mitochondria for ATP
    • flagellum elongates for motility
  5. Oogenesis
    • female gametogenesis
    • forms an ova
    • occurs in the cortex of the ovary
    • pauses prior to birth, resumes at puberty and ceases at menopause
  6. Steps in Oogenesis
    1 Oogonium (2N) --> 1 Primary Oocyte (4N) --> 1 Secondary Oocyte (2N) and 1st Polar Body --> (sperm must be introduced for further development)--> 1 Mature Ovun (1N) and 2nd Polar Body
  7. Oocyte maturation inhibitor
    Secreted by follicular cells in the cortex to inhibit the primary oocyte from maturing in primordial follicles
  8. Ideal age for Oogenesis
    • 18-35
    • if older the primary oocyte may have been dormant too long
  9. Nondisunction
    • failure of homologus chromosomes to separate during meiosis
    • either 24 or 22 chromosomes instead of 23
  10. Trisomy
    • 47 chromosomes (24 and 23)
    • trisomy 21 is Down Syndrome
  11. Monosomy
    • 45 chromosomes (22 and 23)
    • Turnner Syndrom (45, x) is the only survivable monosomy
  12. Oocyte Transport
    • -Secondary oocyte, zona pellucida and corona radiata leave the tertiary follicle
    • -Cilia on the fimbriae of the infundibulum of the oviduct sweep up the oocyte
    • -Peristaltic contractions move the oocyte into the ampula of the oviduct
    • -If unfertilized, oocyte will degenerate in 24 hours
  13. Sperm Transport
    • -Deposited in the fornix of the cervix
    • -Flagellum more thru the endocervical canal
    • -Vesiculase (enzyme) produced int he seminal vesicle forms a sperm plug to decrease backflow
    • -Prostaglandins in semen cause peristaltic contractions thru uterus to the oviducts
    • -200 sperm complete the journy
    • -fertilization in 1-7 hours
  14. Sperm Maturation
    • Fresh sperm can not fertilize
    • Capacitation takes 7 hours
    • -occurs in the uterus and oviduce
    • -the removal of glycoproteins from acrosomal surface
  15. Acrosome Reaction
    • -When sperm contacts the carona radiata perforations develope in the acrosome
    • -acrosome membrane fuses with sperm
    • -acrosomal enzymes are released facilitating fertilization
  16. Hyaluronidase
    Acrosomal enzyme that breaks thru the corona radiata
  17. Acrosin
    Acrosomal enzyme that breaks thru the zona pellucida
  18. Sperm Statistics
    • sperm make up <10% of semen volume
    • 100 million/mL of semen
    • -if <20 million = fretility problems
    • -if < 10 million = steril
    • 10% of sperm are considered abnormal
    • -if >25% are abnormal = fertility problems
  19. Abnormal Oocytes and follicles
    • oocytes with multiple nuclei
    • follicles with multiple oocytes

    presumed to degregade prior to ovulation, but could be capable of fertilization
  20. Fertilization
    • Occurs in the ampulla of the oviduct
    • Chemotaxis directs the sperm to the egg
    • takes up to 24 hours
  21. Phases of fertilization
    • Penetration of corona radiata by hyaluronidase
    • Penetration of zona pellucida by acrosin, causes zona reaction so only 1 sperm can enter
    • fusion of sperm and secondary oocyte plasma membranes= sperm contents enter egg
    • secondary oocyte completes meiosis 2
    • Female and male pronucleus form DNA duplicates in each nucleus
    • Pronuclei fuse with each other forms zygote, sex is determined
  22. In vitro
    • multiple secondary oocytes are harvested from the female
    • they are mixed with capacitated sperm
    • fertilization and zygote cleavage is monitored for 3-5 days
    • 1-2 embryos are emplanted into the uterine lumen
    • remaining embryos are frozen and saved
  23. Cleavage of zygote
    Starts 30 hours after fertilization (still has zona pellucida)
  24. Blastomeres
    Cells formed during zygote cleavage, get progressively smaller
  25. Compaction of zygote
    • occures after the 8 cell stage, necessary step
    • cell adhesion glycoproteins cause increased cell contact
  26. Morula
    name of the zygote at the 12-32 blastomere stage, 3 days after fertilization

    internal cells will become the embry, external cells will become the placenta
  27. Name: Cell, Pink cells, Blue cells, and center cavity
    Image Upload
    • Cell = Blastobyst
    • Pink cells = Embryoblast
    • Blue cells = Trophoblast
    • Center cavity = blastocoele
  28. Mosaic
    nondisjuction in early mitotic cleavage causing 2+ cell lines with different chromosome contents

    may be lost or continue to develop
  29. Blastocyst formation
    • Morula enters the uterine cavity after 4 days
    • fluid diffuses across the zona pellucida
    • day 5: zona pellucida is gone, size increases, blastocyst can freely float in the uterine caivty for 2 days
  30. Monozygotic twins
    • 25%
    • form from one zygote, usually in week 1 the embryoblast divides in the blastocyst
  31. Dizygotic Twins
    • 75%
    • two ova are fertilized by 2 sperm
    • hereditatry tendency of 3x greater
  32. Conjoined Monozygotic Twins
    • Incomplete separation of the embryonic disc
    • Craniopagus- conjoined at the cranium
    • Thoracopagus- conjoined at the thorax
  33. Implantation (week 2)
    • -occurs on days 6-14 after fertilization
    • -the embryonic pole attaches to the uterine endometrium while its in the secretory phase
    • -attaches superiorly and posteriorly in the uterine cavity
  34. Placenta Previa
    Implantation of the blastocyst inferiorly in the uterine cavity. could cover the internal os, cause bleeding and premature separation
  35. Image Upload
    • A- Syncytiotrophoblast (part of trophoblast)
    • B- Epiblast (part of embryoblast)
    • C- Hypoblast (part of embryoblast)
    • D- Cytotrophobalst (part of trophoblst)
  36. Syncytiotrophoblast
    The outer later of trophoblasts which implant into the uterine cavity

    Secrete human chorionic gonadotropin (hCG) which maintains the corpus luteum
  37. Embryonic Disc
    consists of the epiblast and hypoblst
  38. Extrauterine/Ectopic Implantation
    Usually occurs in the oviducts, usually ruptures oviducts and causes hemorrhage into peritoneal cavity. Must be surgically removed
  39. Abdominal pregnancy
Card Set:
Human Development 1
2011-05-07 19:13:29

cards for test 1 of human development
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