The skeletal system is the system that supports us and gives us our shape. Two main structures form the skeletal system: cartilage and bone. Cartilage is largely composed of water and contains no nerves or blood vessels. There are three types of cartilage. Hyaline cartilage provide support with flexibility and resistance. It is the most abundant cartilage. Hyaline cartilage is the cartilage that covers the bone ends at movable joints, connect the ribs to the sternum, form the skeleton of the larynx or voice box, reinforce the passageways of the respiratory system, and forms the end of our nose. Elastic cartilage found in only two locations of the skeletal system which are supporting the external ear and forming the epiglottis. This cartilage is able to stretch and bend repetitively without braking or tearing. Fibrocartilages are cartilages that act as pads to soften the pressure that is exerted from the bones. This cartilage is found in the knee and forms the discs that are between the vertebrae.
Bone provide other important functions for us other than giving shape to the body. For one, they provide a hard framework that is able to support the body and cradle the delicate organs that it contains (One must not also forget that the bones themselves are also living organs.). They provide protection for the internal organs. For example, the fused bones of the cranium protect the brain from injury. The bones also allow for movement in that they are a place for the skeletal muscles to attach. In this way the bones act as levers to move parts of the body. The bones also store minerals that the body needs. The most important of these are calcium and phosphate. The bones are able to store the minerals and then release them into the bloodstream as ions. The bones also form most of the blood cells in the blood; this takes place in the bone marrow.
In all there are 206 named bones in the human skeleton. These are group into the axial and appendicular skeletons. The axial skeleton is formed by the bones of the head and trunk, and the appendicular skeleton is formed by the bones of the upper and lower limbs and the shoulder and hip bones.
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