Blastoderm

The blastoderm is a term for cell layers found in blastulas.

In eutherians

In amniotes

A blastoderm is the layer of cells formed at one pole of macrolecithal eggs such as the yolky egg of birds. The yolk prevents the division from taking place through the egg, resulting in meroblastic cleavage during the many cleavage divisions. At the animal pole (containing less yolk than the vegetal pole), the zygote divides and subdivides, forming the blastoderm, which gradually spreads around the yolk and forms the embryo. The blastoderm is composed of two layers, the epiblast and the hypoblast, which enclose the fluid-filled blastocoel cavity.

See also

• Blastodisc
• Embryology

References

• This article incorporates text from The Modern World Encyclopædia: Illustrated (1935); out of UK copyright as of 2005.
• Campbell Reece, Biology 7th edition, Pearson Publishing, 2005