Which of the following is not correct for gastrulation [RPMT 2002]
A) Archenteron is formed
B) All germinal layers are formed
C) Morphogenetic movements
D) Some blastomeres & blastocoel degenerate
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The most likely incorrect statement for this would be 
Gastrulation is the process that helps the direct formation of
or forms 
which are three in number, or, three germ layers in total.
The Sum total of all the required processes which are contributing in the conversion of a solid ball of cells or hollow ball of cells or many layered discs of blastula (Multicellular ball-like embryonical structure produced usually at the end of cleavage and is having a fluid filled with blastocoel, called blastula) into two (observed in coelenterates) or in three (starting and observed from platyhelminthes to other groups and/or species) germinal layers of gastrula is summed up as Gastrulation.
This is the most early phase regarded in the most early embryonical development of select advancements of organs in a organism. Gastrulation takes place by the migratory or formative or morphogenetic movements of several blastomeres from the surface of blastula to the properly positioned place in gastrula. All the movements are classified as the following. The movements of gastrulation have seen the involvement of an embryo as a whole, here, the coordination of other movements occurring throughout simultaneously must be in cordial with cellular migrations on some applied parts of an embryo undergoing gastrulation (in short, attributed to different practicalities):
a) Epiboly: Not occurring in embryos of humans, as, Epiboly is never seen. Epiboly is the growth of one part over another part like prospective ectoderminal layers spreading over the rest of the embryos body except the blastomeres.
b) Emboly: These are morphogenetic movements which contribute and promote the migration of ectoderminal layer, mesoderminal layer and primarily notochord cells (important component) from the surfaces to the interior cells. The emboly may (or may not) occur by the way or direction of:
i) Involution: The rolling of cells into interior and deeper bodies or The more inturning or a basically a inward movement of an outer layer or ectoderminal layer which is expanding, as so, to spread the internal surfaces over the rest of remaining external cellular structures. Simply stated, it is the inturnment of cellular sheets over the basal surfaces of an outermost layer (ectoderm). Good example here is a typical Amphibian.
ii) Invagination: It's main process will be the infolding of a cell controlled in those applied regions (due to some exceptions like blastomeres) of cells formed already. There is a indent inside the interior structures well attributed to delicate structures when it has been touched or squeezed. In all, the infoldment of cellular sheets into embryo in Invagination. Good example following this process would be hollow coleomates called Sea Urchins. Note: Endoderm is the main region to get affected when this process ends.
iii) Ingression: New cells are often found undergoing migrations into the liquid of blastocoel and/or the migration of individual created cells from a cellular sheet present in the surface deep into the interior layers of embryo. Good example again is the Sea Urchin (region formations : mesoderminal layers), Drosophila (regional formations : neuroblastoma cells are the tumor forming agents and/or neuroblasts if considered about specific region).
iv) Delamination: This is a process of or formation by which a second layer is evenly formed by tangential divisions of the cellular sheets present in the surface. Here, the cellular sheets are divided or the splitting of those cellular sheets are then forming one or two parallel sheets or splitting of one sheet into two sheets. Good example would be us! that is, Mammalian species and birds or avians (main enacting region would be hypoblast formation).
During the whole process of Gastrulation, the blastocoel is obliterated or removed or destroyed for the formation of a new cavity called archenteron or gastrocoel (specifically lined by the cells of endoderm). Gastrocoel is formed which is a future or upcoming alimentary canal of the animal. Blastopore is the opening of archenteron not present in amniotes.
Gastrulation is the process that helps the direct formation of
The Sum total of all the required processes which are contributing in the conversion of a solid ball of cells or hollow ball of cells or many layered discs of blastula (Multicellular ball-like embryonical structure produced usually at the end of cleavage and is having a fluid filled with blastocoel, called blastula) into two (observed in coelenterates) or in three (starting and observed from platyhelminthes to other groups and/or species) germinal layers of gastrula is summed up as Gastrulation.
This is the most early phase regarded in the most early embryonical development of select advancements of organs in a organism. Gastrulation takes place by the migratory or formative or morphogenetic movements of several blastomeres from the surface of blastula to the properly positioned place in gastrula. All the movements are classified as the following. The movements of gastrulation have seen the involvement of an embryo as a whole, here, the coordination of other movements occurring throughout simultaneously must be in cordial with cellular migrations on some applied parts of an embryo undergoing gastrulation (in short, attributed to different practicalities):
a) Epiboly: Not occurring in embryos of humans, as, Epiboly is never seen. Epiboly is the growth of one part over another part like prospective ectoderminal layers spreading over the rest of the embryos body except the blastomeres.
b) Emboly: These are morphogenetic movements which contribute and promote the migration of ectoderminal layer, mesoderminal layer and primarily notochord cells (important component) from the surfaces to the interior cells. The emboly may (or may not) occur by the way or direction of:
i) Involution: The rolling of cells into interior and deeper bodies or The more inturning or a basically a inward movement of an outer layer or ectoderminal layer which is expanding, as so, to spread the internal surfaces over the rest of remaining external cellular structures. Simply stated, it is the inturnment of cellular sheets over the basal surfaces of an outermost layer (ectoderm). Good example here is a typical Amphibian.
ii) Invagination: It's main process will be the infolding of a cell controlled in those applied regions (due to some exceptions like blastomeres) of cells formed already. There is a indent inside the interior structures well attributed to delicate structures when it has been touched or squeezed. In all, the infoldment of cellular sheets into embryo in Invagination. Good example following this process would be hollow coleomates called Sea Urchins. Note: Endoderm is the main region to get affected when this process ends.
iii) Ingression: New cells are often found undergoing migrations into the liquid of blastocoel and/or the migration of individual created cells from a cellular sheet present in the surface deep into the interior layers of embryo. Good example again is the Sea Urchin (region formations : mesoderminal layers), Drosophila (regional formations : neuroblastoma cells are the tumor forming agents and/or neuroblasts if considered about specific region).
iv) Delamination: This is a process of or formation by which a second layer is evenly formed by tangential divisions of the cellular sheets present in the surface. Here, the cellular sheets are divided or the splitting of those cellular sheets are then forming one or two parallel sheets or splitting of one sheet into two sheets. Good example would be us! that is, Mammalian species and birds or avians (main enacting region would be hypoblast formation).
During the whole process of Gastrulation, the blastocoel is obliterated or removed or destroyed for the formation of a new cavity called archenteron or gastrocoel (specifically lined by the cells of endoderm). Gastrocoel is formed which is a future or upcoming alimentary canal of the animal. Blastopore is the opening of archenteron not present in amniotes.
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