Structure of the Human Skeleton
The human skeleton is made up of 206 bones and its structure classified in many ways, including by bone type and by location. While the human skeleton has many functions, its main functions are those of support, protection and movement of the body.
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Skeletal Classification
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The 206 bones in the human skeleton can be classified into five groups based on shape. Long bones are longer than they are wide: these are the large bones in the arms and legs as well as those in the fingers and toes. Short bones are about as long as they are wide and include the bones in the ankles and wrists. Flat bones are, as the name suggests, flat and usually function to protect organs such as the heart (ribs, sternum) or brain (skull). Irregular bones are not easily categorized by shape, and can be found in places such as the spinal column and the inner ear. Sesamoid bones are very short bones embedded within a tendon. The kneecap is an example of a sesamoid bone.
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Skeletal Position
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Another way in which the human skeleton can be classified is by position, as appendicular and axial. The appendicular skeleton is made up of the bones of the appendages (i.e., arms and legs). The axial skeleton consists of the head, spinal column and ribs.
Skeletal Connections
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The bones in the human skeleton are held together by tendons and ligaments, which are types of connective tissues. While ligaments connect bone to bone, tendons connect muscle to bone. On the surface of each bone are tubercles, or bumpy parts that serve as connection points for tendons and ligaments.
Skeletal Movement
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Joints are found where two bones meet. These joints can be fibrous, cartilaginous or synovial. Fibrous joints do not allow movement and can be found in the skull (which is made up of many bones) and the pelvis. In cartilaginous joints the bones are connected by a piece of cartilage; this type of joint is found in the ribs and between the vertebrae in the spinal column. Most joints in the body are synovial joints. These allow for free movement are found in such places as the neck, arms, wrists, fingers, ankles, legs and toes.
Skeletal Function
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The human skeleton's structure performs many functions. The bones in the skeletal system protect vital organs. The rib cage protects the heart and lungs, the skull protects the brain and the spinal column protects the spinal cord. The muscles, tendons, ligaments and joints in the skeletal system all give the body structure and promote movement. Minerals such as calcium and phosphorus are stored in the bone tissue and released into the bloodstream when needed for body functions. Finally, the marrow inside the cavities of large bones such as the femur and pelvis is responsible for the creation of blood cells.
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