Question

What is the fourth germ layer?

Answer 1

Neural crest (fourth germ layer):

1. As the neural tube is closing and separating from the general cutaneous ectoderm, a population of cells called the neural crest leaves the dorsal part of the neural tube and begins to spread throughout the body of the embryo.
2. The neural crest produces an astonishing array of structures in the embryo, and its importance is such that the neural crest is sometimes called the fourth germ layer of the body.
3. The neural crest forms an exceptionally wide range of cell types and structures, including several types of nerves and glia, connective tissue, bones, and pigment cells.
4. Its importance and prominence are such that the neural crest has often been called the fourth germ layer of the body.