AIPMT-NEET Biology Aspirants, read out the next AIPMT-NEET Biology Study material/ Notes of Gastrulation. In this we will learn about movements involved in gastrulation important for AIPMT-NEET Biology. Free online notes for AIPMT-NEET.

During the cleavage of the fertilized egg, new cells form and their position is established. During gastrulation, these cells are rearranged by specific movements to give new position and new neighbours. Overall multilayered body plan of the organism is established during gastrulation.

Three germ layers of the body form during gastrulation: Inner Endoderm, Outer Ectoderm and interstitial Mesoderm.

Following are the basic type of cell movements involved in gastrulation:

• Invagination – is infolding of the region of cells/ cell sheet into embryo. E.g endoderm of sea urchin
  

  Invagination

• Involution –is inturning or inward movement of an expanding outer layer of cell so that it spreads over the internal surface/ basal surface of the existing outer layer. E.g. mesoderm of amphibian

Involution

• Ingression – is migration of individual cells from the surface layer into the interior of the embryo. These cells migrate independently. E.g. mesoderm of sea urchin, drosophila neuroblasts (embryonic cells which form nerve fibers)

Ingression

• Delamination – is splitting of one cell sheet into two or more parallel sheets. E.g. mammalian and bird hypoblast formation.

Delamination

• Epiboly – is the expansion of one cell sheet over the other cells. It encloses the deeper layers of the embryo. E.g. ectoderm formation in sea urchin, ambhibians.

Epiboly