| Embryology of sea urchin: early gastrula (initial phase) |
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Legend:
1 ectoderm
2 begin of archenteron
3 endoderm
4 blastoecoel (central)
5 direction of invagination
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English name: Sea urchin
Scientific name: Psammechinus sp.
Familia: Echinidae
Classis: Echinoidea
Phylum: Echinodermata
Regnum: Animalia
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Blastomeres migrate from the vegetal pole inward during the so-called invagination or gastrulation process (according to the direction of the arrows at 5). In this way the ecto- and endoderm are formed. The endoderm covers the developing primitive gut, called archenteron (arche = original - primitive, enteron = gut).
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