Gastrulation (comparative account of Gastrulation)

Gastrulation of developmental biology

1. Smart Study 1
2.2
Content :
Comparative account of Gastrulation
Morphogenetic Movement
Types of Morphogenetic Movement
1. Epiboly
2. Emboly
Comparative account of Gastrulation

2. Comparative account of Gastrulation:
The blastula of animal consists of numerous cells (blastomeres).
The position of blastomereswere established during cleavage.
During gastrulationthese cells are given new position and the multi-layered
body plan of organism is established.
The cells that will form the endodermaland mesodermalorgans are brought to
the inside of the embryo while the cells that will form the skin and nervous
system are spread over its outside surface.
Thus,thethree germ layers -outer ectoderm,innerendoderm and interstitial
mesoderm are produced during gastrulation.Thestage is set for the interaction
of tissues.
Smart Study 2
2.2

3. Smart Study 3

4. •The Migration of cells of organ specific area from the surface of blastula to
their progressive position described as Morphogenetic movement because
such moment helps in morphogenesis (development of a particular structural
pattern).
•The morphogenetic movements that occur during embryogenesis are of
Irreversible nature while those of adult are reversible.
•There are only few basic types of cell movments
•The three primary germ layers get differentiated as a result of these
movements
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Morphogenetic Movement2.2

5. 1.Epiboly-The expansion of one cell sheet over other cells.
•Blastomeresspreads over presumptive endodermal cells.
•Blastomeresmoves from animal pole to vegitalpole.
•Epiboly can occur bycellsdividing, by the cells changing their shape or by
several layers of cells intercalating into fewer layers.
•Result -Ectoderm fomation
•Example -Ectoderm formation in amphibians, sea urchins and tunicates
Smart Study 5
1. Epiboly

6. Smart Study 6
2.Emboly

7. B. Ingression-Migration of individual cells into the embryo
from the surface layer. The cells became Mesenchymal( i.e.,
they separated from one another )and migrate independently
Example –
1.Mesoderm formation in sea urchins
2.Neuroblastsformation in Drosophila.
3.Endoderm and Mesoderm formation in birds
4.Primary hypoblast formation in birds.
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B. Ingression

8. C. Delamination
The splitting of one cellular sheet into One or two parallel sheets.
Result -The formation of a new sheet of cells.
Example -Mammalian and bird Hypoblast formation.
D.Involutioninward movement of an expanding outer layer so that it
spreads over the internal surface of the remaining external cells.
Example -Amphibians Mesoderm.
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C. Delamination
D. Involution