The skeleton system provides the framework which supports the body and maintains its shape. The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. It serves as a scaffold which supports organs, anchors muscles, and protects organs such as the brain, lungs and heart. Hematopoiesis is also an important function of bones. This is the process of red blood cell formation and is carried out by stem cells in active red bone marrow. There are 206 bones in the adult human skeleton and two main parts of the skeleton: the axial skeleton, including the bones of the head and trunk, and the appendicular skeleton, including the bones of the limbs. The axial skeleton has 80 bones and the appendicular skeleton has 126 bones. Axial Skeleton. The axial skeleton includes the skull, the spine, and the ribs and sternum. The most important of these is the spine (called also the spinal or vertebral column), consisting of 26 separate bones. Twenty-four vertebrae have holes through them, which are lined up vertically to form a hollow tube called the spinal canal; the spinal cord runs through this canal and is protected by it.