Germ layer

When cotyledons are called in developmental biology of tissue animals a first differentiation of an embryo into different cell layers from which subsequently develop different structures, tissues and organs. The cotyledons formed during gastrulation of the blastula.

The animals are bilaterally symmetrical triploblastisch, i.e., they form the three germ layers of:

• Endoderm / endoderm (inner layer)
• Mesoderm (middle layer )
• Ectoderm (outer layer )

Only two cotyledons form the diploblastischen tribes of the Cnidaria and Ctenophora.

The ' conversion ' of cells of a cotyledon to one another is called transdifferentiation.

• Embryology
• Developmental Biology