ch 14 pt 4

• what does the ICM differentiate into around day 8?

  bilaminar germ disc (contains upper epiblast (embryo and amnion)and lower hypoblast (yolk sac))
• name the proteins that are expressed around days 7-8 in the human bilaminar germ disc

  OCT-4 (epiblast), GATA-6 (hyphoblast?), GATA-3 (throphoectoderm)
• what is the name if the group of enlarged cells found 2 weeks after fertilization at the anterior pole that mark the region that will induce the brain

  prechordal plate
• what is found at the posterior end during gastrulation and placenta

  a stalk connects the embryo to the trophoblast and becomes the umbilical cord
• primitive streak


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• when does the primitive streak form in humans and what does it contain

  15-17 days after fertilization
• important distinct cell groups through single cell analysis

  1. endothelial precursor cells
  2. erythrocytes
  3. primordial cells
• what does the connecting stalk connect and what does this region eventually become?

  links the embryo to the trophoblast eventually forming the vessels of the umbilical cord
• what does the chorion consist of

  throphoblast tissue and blood vessel-containing mesoderm
• what does the chorion eventually become

  placenta
• what part of the placenta does the chorion form

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• what are the basic differences between fraternal twins and identical twins

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• differences in extraembryonic membranes in relation to the timing of human monozygotic twinning

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• when do conjoined twins arise? when do fraternal twins arise?

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• the rationale performed in chicks that have influenced scientists understanding of the different types of conjoined twins

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