The skeleton forms the internal framework of the body upon which the soft tissues are deployed. This is not a static framework, but a dynamic internal scaffold. It is dynamic in many ways. On one hand, it shows extreme flexibility of movement when acted upon by muscles. At another extreme, the cells of skeletal tissue are constantly monitoring and changing the microstructure of this amazing tissue called bone, providing it with maximal strength, toughness, and resilience. In addition to its dynamic role of support it also provides a protective and stabilizing function. The cranium and vertebral column surround the delicate central nervous structures, the brain and spinal cord, providing a strong, protective shell. This protective case, called the cranium, also fixes in space important nervous structures, such as the internal ear, that would not be able to function properly in an unstable environment. This dynamic framework also exhibits a tremendous capacity for growth and repair. It is a dynamic storehouse of calcium ions, ions that play a significant role in many of the body's functions. The skeleton consists of 206 separate bones, ignoring various sesamoid bones and the fact that some bones represent the fusion of multiple bones. These bones range in size from the small ear ossicles measuring a few millimeters in length, to the large femur measuring up to fifty centimeters. The skeleton is divisible into two portions, the axial skeleton and the appendicular skeleton. The axial skeleton includes the cranium, vertebral column, ribs, and sternum. The appendicular skeleton consists of the bones of the limbs and their girdles. The individual bones of the skeleton come in a variety of shapes. Some are long and tubular, while others have the spread-winged appearance of a butterfly. In the right hands, the skeleton can be a library of information. Its markings, foramina, landmarks, and canals each tell a story about the soft tissues of the body. A strong foundation of skeletal anatomy goes a long way.