Without your skeletal system, your body would be unsupported, and without your bones and muscles working in tandem, you would be unable to move. The muscles and bones together are often referred to as the musculo-skeletal system. Your bones also control the production of blood cells and release of minerals into the bloodstream.
Purpose
The skeletal system protects vulnerable organs from injury, particularly the skull which cradles the brain, and the sternum and ribcage, which encase the heart and lungs. The marrow inside some bones plays an important role in replacing the body's store of red blood cells, according to the Wake Forest University Baptist Medical Center website. Bones are also the body's storehouse for necessary minerals such as calcium and phosphorus. Bones give the muscles a place to attach, allowing the body to move.
Axial Skeleton
The axial portion of the skeleton--the skull, hyoid bone, vertebral column and sternum--is aligned along the body's long axis. These bones support and protect the organs from the head to the trunk. The skull includes cranial and facial bones, which protect the brain and give shape to the face. The sternum and ribs protect heart, lungs and major blood vessels. The ribs also protect parts of the spleen, kidneys and stomach, and assist the lungs in breathing. The vertebral column allows the body to stand upright and move freely.
Appendicular Skeleton
The appendicular portion of the skeleton consists of the bones outside the body's main axis--those of the upper and lower extremities, and the shoulder and pelvic girdles. Bones of the upper extremities include those of the hands, forearms and arms. Lower extremity bones include those of the leg, foot, thigh and patella, and are the largest and heaviest in the whole body and bear the most weight. The thigh's single bone, the femur, is the longest and strongest of all human bones, according to Minnesota State University. The shoulder and pelvic girdles connect your limbs to your trunk and provide freedom of movement.
Bone Types
Bones are generally classified as one of four types: long, short, flat or irregular. Examples of long bones are those of your arms and legs. Longer than they are wide, long bones act as levers. Short bones, which are club-shaped, are found in the wrists and ankles. The greater surface area of the flat bones, which include the ribs, cranial bones and shoulder girdle bones, provides protection for the organs and a place for muscles to attach. Irregular bones, such as vertebrae and some skull bones, are those that do not fit in the other categories.
Bone Composition
The tissue inside a bone can be either compact or spongy, and most bones contain both types. The compact tissue is dense, forming a hard protective layer on the outside of the bone. Spongy tissue, found on the inside of most bones, is porous and consists of many tiny holes. Bone tissue consists of different types of bone cells, each having a particular function (such as controlling calcium release or bone growth and healing). Bone tissue also contains minerals such as calcium and phosphorus, which give bones strength, and a fibrous substance that gives bones flexibility.
