The brain cover is composed of three layers: the CORTEX, pia, and dura. The CORTEX is the outermost layer and is made up of folded gray matter. The pia is the middle layer and is a thin membrane that covers the surface of the brain. The dura is the innermost layer and is a tough, fibrous membrane that surrounds the brain and spinal cord. Together, these three layers form the protective covering for the brain.