Jeanmarie Hill, age 10, of Pocatello, Ids., for her question:
HOW MANY BONES ARE IN THE BODY?
Your flexible, bony framework is called a skeleton. It gives your body shape, protects vital organs and provides a system of levers, operated by muscles, that enables your body to move. Your human skeleton has 206 separate bones.
A skeleton houses bone marrow, the blood forming tissues. It stores elements such as sodium, calcium and phosphorus, and releases them to the blood. It also holds reserves of protein that the body uses during fasting.
A human being generally forms the 206 separate bones out of cartilage as he develops to maturity. Sixty four of these bones are in the hands and arms alone.
Bones are connected to neighboring bones by joints. Joints are either immovable, as in the skull, or movable, as in the arms and legs. The bones fit together and are held in place by strong bands of flexible tissue called ligaments.
The human skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton.
The axial skeleton is made up of the bones of the head, neck and trunk. The spine or backbone forms an axis that supports the other parts of the body. The skull is at the top of the spine. The spine consists of separate bones called vertebrae, with fibrous discs between them.
The 12 thoracic vertebrae are at the back of the chest and attached to them are the ribs. Each side usually has 12 ribs. The upper ribs fasten in front to the sternum or breastbone. The ribs protect the heart and lungs and act as a bellows box for the breathing process.
The appendicular skeleton consists of bones of the arms and legs.
The shoulder girdle consists of the scapula, humerus and clavicle or collarbone.
The skeleton of the arm is divided into the shoulder blade, the upper arm and the forearm. Next come the wrist bones, hand bones and fingers. The leg includes pelvic, thigh, leg, foot and toe bones.
More about the axial skeleton: five lumbar vertebrae lie in the lower part of the back. Below the last lumbar vertebra is the sacrum. In babies, five separate bones make up the sacrum. In adults, these bones have grown together into one solid structure.
The pelvis is attached to the sacral segment of the spine by sacroiliac joints. The coccyx is at the bottom of the spine. In children, four separate bones make up the coccyx. But these bones have fused by the time a person is about 25.
The point where the sacrum and coccyx meet remains fibrous throughout life.
Most backboned animals have two pairs of limbs: front and hind limbs. Most mammals are quadruped, which means they run on all four legs. Man is a biped, because walks on only two legs.
A giraffe’s neck has the same number of bones as a mouse’s neck, although the giraffe’s bones are much longer and larger.