Germ layers

Definition

Germ layers are the primary layers of cells that form during embryonic development. These layers differentiate into various tissues and organs in animals.

5 Must Know Facts For Your Next Test

1. The three primary germ layers are ectoderm, mesoderm, and endoderm.
2. Ectoderm gives rise to the nervous system and skin.
3. Mesoderm forms muscles, bones, and the circulatory system.
4. Endoderm develops into the lining of the digestive and respiratory systems.
5. Germ layer formation is a key process in early embryogenesis called gastrulation.

Review Questions

• What are the three primary germ layers formed during embryonic development?
• Which germ layer differentiates into the nervous system?
• During which process do germ layers form in animal embryos?

Related terms

Ectoderm: The outermost germ layer that forms structures such as skin and the nervous system.

Mesoderm: The middle germ layer that gives rise to muscles, bones, and the circulatory system.

Endoderm: The innermost germ layer that develops into internal linings of organs like the digestive tract.