The Brain is the enlarged anterior part of the central nervous system within the skull. The young adult human brain weighs about 1,450 g, and its outer layer (the cerebral cortex) contains over 10 billion nerve cells. The brain develops by differentiation of the embryonic neural tube along an anterior-posterior axis to form three main regions—the forebrain, midbrain, and hindbrain—that can be further subdivided based on anatomical and functional criteria. The cortical tissue is concentrated in the forebrain, and the midbrain and hindbrain structures are often considered together as the brainstem.
