The 206 bones that make up the skeleton are divided into two categories, the axial skeleton (trunk and head) and the appendicular skeleton (arms and legs). These three bone layers work together to handle the skeletal system. The inner layer of the periosteum contain cells that produce bone. Each bone is covered by the periosteum, which is a layer of specialized connective tissue and acts as the skin of the bone. This dense layer of compact bone supports the weight of the body and is mainly compromised of calcium and minerals. Nerves and blood vessels run through the passages that supply oxygen and nutrients to the bone. Cylindrical in shape, the dense layers of the compact bone are honeycombed with thousands of tiny holes and passages. Surrounding the marrow is a dense rigid bone called the compact bone. Yellow marrow consists mainly of fat cells. The red marrow produces red blood cell, which carry oxygen, white blood cells, which fight infection, and platelets, that help stop bleeding. Within the long bone is a central marrow cavity known as bone marrow. There are 126 bones in th appendicular skeleton: 60 in the upper extremities, 60 in the lower extremities, 2 in the pelvic girdle, and 4 in the shoulder girdle.Įach of these 206 bones consists of three layers: the bone marrow, compact bone and the periosteum. There are 8o bones in the axial skeleton, consisting of the skull, spine, ribs and and sternum. The skeleton consists of the axial and appendicular skeleton. Bones serve as banks for storage and release of minerals like calcium and phosphorous.Our skeletal system serves as a framework for other tissues and organs.Our skeletal system protects our organs.Bones serve as levers that transmit muscular forces.

The skeletal system serves several important functions in the body: The human adult skeleton has 206 bones joined to ligaments and tendons to form a supportive and protective framework for underlying soft tissues and muscles.

Long bones flat bones