Embryology Lecture 1: From Fertizilation to Gastrulation

Bottom Line
1. Fertilization in ampulla of uterine tube
  1. fusion of pronuclei -> division of blastomeres -> MORULA -> compaction of blastomeres so fluid into center -> BLASTOCYST w/fluid filled cavity & inner cell mass = EMBRYO; outer cell mass = TROPHOBLAST
  2. pregnancy -> syncytiotrophoblast secretes hCG -> maintains corpus luteum -> makes progesterone -> maintain pregnancy
2. Infertility 15-30%; ART ^ prematurity, low birth weight, & birth defects
  1. no fertilization -> no hCG -> corpus luteum regresses -> no progesterone -> menstruation & prep for next cycle
3. 2nd Week
  1. Trophoblast
    1. Cytotrophoblast (makes cells)
    2. Syncytiotrophoblast (forms syncytium - blastocyst into uterine endometrium))
  2. Inner cell mass @ one pole of blastocyst -> germ disc (epiblast & hypoblast)
  3. 2 cavities - amniotic (dorsal to epiblast); yolk sac (ventral to hypoblast)
  4. syncytio - this whole part - ASK QUESTIONS WHAT IS HAPPENING
  5. "Week of 2s" - 2 layers trophoblast (synctio- and cytotrophoblast), 2 layers embryoblast (epiblast & hypoblast), 2 cavities (amniotic & yolk sac - then chorionic cavity), 2 layers extraembyonic mesoderm (somatic & splanchnic)
4. 3rd Week - GASTRULATION
  1. 3 Germ Layers from epiblast
    1. Ectoderm
      1. Skin, CNS, PNS, eyes, internal ear, neural crest cells
    2. Mesoderm
      1. bones, connective tissue, urogenital system, cardiovascular system
    3. Endoderm
      1. gut & gut derivatives (liver, pancreas, lungs, etc)
  2. 3 cavities - amniotic, yolk sac, chorionic

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Embryology Lecture 1: From Fertizilation to Gastrulation

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