I.
Development
a.
Stages of development (humans)
i.
Cleavage
ii.
Blastulation
iii.
Gastrulation
iv.
Organogenesis
1.
neurulation
2.
other systems
b.
control of development
i.
what controls?
1.
cytoplasmic substances
2.
induction
ii.
evidence/cloning
Fig 49-14, page 973
Morula
•
about 32 blastomeres
•
nearing uterus
•
3 days old
Blastulation
•
Change in structure but not in size
o
Changing internal organization
o
Going from solid mass to hollow structure
o
Cells moving outwards
•
Blastula/blastocyst
In humans:
•
From outside looks like sea urchin (about 7 days old)
•
Outer layer is called trophoblast
gives rise to placenta
•
Inner cell mass becomes embryo
•
Space is blastoseal
Human blastocyst:
•
Outer layer endometridum
•
Separating layer tropoblast
•
Little dark spot embryo
•
P 974
Twins:
Identical (monozygotic):
•
Totipotency
-- can give rise to anything in the placenta
•
Pluripotency – starts to narrow down can only adult organs
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Conjoined twins:
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- Spring '11
- Martin
- Developmental Biology, inner cell mass, yolk sac
-
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