Brain

This entry describes the formation of the brain through seven developmental stages and describes various factors that can influence the process of development. Of the three germ layers (endoderm, mesoderm, ectoderm) that form during gastrulation (the process of forming the trilaminar layer from the single-layered blastula) in the embryo, the brain arises from the neural crest of the ectoderm. This simple cell layer provides the origin for the human brain, deemed the most complex object in the universe. The brain is composed of two main classes of cells: neurons and glia. Each of these major classes of cells is made up of many cell subtypes. Neurons are the cells that process and share information acquired from sensory receptors to produce behavior.

The three principal types of ...