Gastrulation:
It is the third stage of development after Morula and Blastula stage. It is the most dynamic stage of the embryonic development. Gastruation results in the formation of three germinal layer called Ectoderm, Mesoderm and Mesoderm.
Gastrulation is charecterised by the following events:
(i) Cell proliferation:
(a) It is the process of increase in the number of the cells of an embryo.
(b) It occurs due to the division of both tropoblast and embryoblast.
(ii) Cell Movement:
(a) It is the movement of embryo making cell
(b) It is also called morphegenetic movement
(c) In the case of human being the cell movement involves the cell movement involves the movement of embryoblast and resulting in the formation of three germinal layer as follows:
• Endoderm:
→ It is the first germinal layer formed
→ Endoderm formed from the lowermost cells of the embryoblest arranged around a carity of lumen called as Archenteron or Gastrocoel
→ Archenteron developes into the "gut" of the future embryo
→ Formation of embryonic disc: The remaining cells of embryobles now cansolidate and stretch to form the embryonic dise.
• Mesoderm
→ Cells of the embryonic disc profile rates and arranged at the caudal region from where they finally deattached to arrange between endoderm and the embryonic disc to form the mesoderm
• Ectoderm:
→ It forms the outer surface of an embryo develops from epiblast of the embryo
→ The ectoderm develops into the surface ectoderm, neural crest and the neutral tube
