acrosomal depolarized: Na ions flow in;
Cortical reaction -> slow block to polyspermy sea urchin.
fertilization QH442.2 .C743 2002: Creation#23:30 woman egg donor, Judson's skin cells thru zona pellucida (glycoprotein) - 32:30

cleavage Echinoderm include Echinoidea. sea urchins; 5-7 devisions (128)
gastrulation-urchin Vegetal pole: has yolk (not in mammals).
germ_layers Prefix ecto: outer, external; epi: above, top.
organogenesis-frog Neural crest -> skull, etc. Archenteron from endoderm.
organogenesis-chick Chickens hatch 21 days.
embryonic REVU epiblast, hypoblast -> yolk sac. Prefix tropo: turning, change; epi: above, top. Trophoblast implants by digesting enzymes.
embryonic2 Placenta also contains mesoderm.
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SQ: 1=a       3=e  
AQ: 1=e  2=a  3=b  4=e  5=d  6=b  7=d  8=c
CQ:                     5=a  6=c  7=c  8=a           17=a

0. Vitelline (yolk of an egg) layer: meshwork of extracellular matrix molecules under jelly coat.
1. Somites: give rise to segmental structures such as vertebrae and skeletal muscle.
2. Neural crest along border where neural tube pinches off from ectoderm, form peripheral nerves, teeth, skull bones, many other cell types.
3. Archenteron: primitive gut, open end of archenteron is blastopore, will become anus.
4. Frog: yolk–laden cells im vegetal hemisphere of embryo.
5. Allantois: precursor of umbilical cord
6. Blastocyst: mammalian version of blastula