Human skeleton

The skeleton changes composition over a lifespan. A developing fetus has no hard skeleton at all - it forms gradually during the nine months in the womb. When a baby is born it has more bones than it will as an adult. On average, an adult human has 206 bones in their skeleton (the number can vary slightly from individual to individual), but a baby is born with approximately 270. The difference comes from a number of small bones that fuse together during growth. These include the bones in the skull and the spine. The sacrum (the bone at the base of the spine) consists of six bones which are separated at birth but fuse together into a solid structure in later years.

There are 6 bones (three on each side) in the inner ear that articulate only with themselves, and one bone, the hyoid[?] bone, which does not touch any other bones in the body.

The longest bone in the body is the femur and the smallest is the stapes bone in the inner ear.

Function The skeleton functions not only as the support for the body but also in haematopoiesis, the manufacture of blood cells that takes place in bone marrow.

Gender differences There are small differences between the male and female human skeletons. Men tend to have slightly thicker and longer limb bones while women tend to have larger pelvic bones in relation to body size.

Organization One way to group the bones of the human skeleton is to divide them into two groups, namely the axial skeleton[?] and the appendicular skeleton[?]. The axial skeleton consists of bones in the midline and includes all the bones of the head and neck, the vertebrae, ribs[?] and sternum[?]. The appendicular skeleton consists of the clavicles, scapulae, bones of the upper limb, bones of the pelvis and bones of the lower limb.

Key parts of the human skeleton include:

• skull
• jaw
• rib cage
• spine
• pelvis and (hip)
• femur
• tibia and fibula[?]
• humerus
• radius and ulna
• patella[?] (knee cap[?])
• wrists and ankles[?]
• hands and feet

Diseases The skeleton can be affected by many diseases, affecting physical mobility and strength. These range from minor to extremely debilitating. Bone cancer and bone tumors[?] are extremely serious and often require amputation of the affected limb. The various forms of arthritis attack the skeleton and cause extreme pain and debility. Osteoporosis is another danger, especially for post-menopausal women and the elderly. It greatly increases the likelihood of fractures and broken bones, although they can happen to anyone at any time if the bones suffer a trauma.

See also skeleton, list of bones in the human skeleton.