Which germ layer gives rise to the skin and nervous system?

• A. Ectoderm
• B. Endoderm
• C. Mesoderm
• D. Hypodermis

Answer: (A)

Ectoderm is the germ layer that forms the skin and nervous system. In early development, the outermost layer, the ectoderm, gives rise to the epidermis—the skin’s outer layer—as well as all neural tissue. The neural plate, derived from ectoderm, folds to create the brain and spinal cord, and neural crest cells from the ectoderm contribute to many components of the peripheral nervous system and other structures. By contrast, the endoderm becomes the lining of the gut and related organs, and the mesoderm forms muscles, bones, blood vessels, and other middle tissues. The hypodermis isn’t a germ layer; it’s the subcutaneous layer beneath the skin, mainly derived from mesoderm.