The skeleton supports the body, protects internal organs, provides for movement, stores mineral reserves, and provides a site for blood cell formation.
The skeleton is like the wooden frame of a house.
Bones also protect the internal organs of the body. For example, the skull protects the brain, and the ribs protect the lungs.
They are also a system of levers that control muscles.
Bones are also the site of blood cell formation.
Blood cells are produced in soft marrow tissue that fills the internal cavities in some bones.
There are 206 bones in the adult human skeleton.
The bones can be divided into two parts, the axial skeleton and the appendicular skeleton. The axial skeleton supports the central axis of the body. It consists of a skull, the vertebral column and the rib cage. The bones of the arms and legs along with the bones of the pelvis and shoulder area, from the appendicular skeleton.
Bones are a solid network of living cells and protein fibers that are surrounded by deposits of calcium salts. The bone is surrounded by a tough layer of connective tissue called the periosteum. Blood vessels that pass through the periosteum carry oxygen and nutrients to the bone. Beneath the periosteum is compact bone. It is dense and within it runs tubes called Haversian canals. They contain blood vessels and nerves. Underneath that is the spongy bone. Finally, the inner part of the bone is called marrow. There are two types of marrow, yellow and red.
Yellow is made of fat cells and red produces blood cells, some kinds of white blood cells and platelets.
The skeleton of a newborn is composed almost entirely of cartilage. Cartilage is replaced by bone through ossification.
Depending on its type of movement, a joint is classified as immovable, slightly movable and freely movable.
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