In this topic you will learn about the bones in your body.

Your body has many bones. These bones make up the skeleton. A skeleton is a supporting frame that gives the body its shape and protects the organs. A skeleton has many jobs. It gives your body shape and helps you move your body. The skeleton protects some organs. For example, the bones of the skull protect the brain.

All bones have a similar structure. The solid part of the bone is made of layers of minerals like calcium and phosphorous. A bone is covered with a tough but thin membrane that has many blood vessels. Inside bones is a soft tissue known as marrow. Red marrow fills the spaces in spongy bone. Red marrow makes new blood cells. The marrow also makes germ-fighting white blood cells.

The skeleton has many types of joints. A joint is a place where two bones meet. There are three main types of joints: immovable joints, partly movable joints, and movable joints. Immovable joints are places where bones fit tightly together, as in your skull. Partly movable joints are places where bones can move only a little, as where the ribs are connected to the breastbone. Movable joints are places where bones can move easily, as in your wrist or your hip.

Your skeleton is made of more than just bones and joints. A ligament is a tough band of tissue that holds two bones together where they meet. Ligaments are tough, but they stretch easily when a joint bends.

Cartilage is a flexible tissue that covers the ends of some bones. It helps protect them from grinding against one another at a joint. Cartilage can also be found in the tip of the nose.

If you hurt your skeleton, it is important to get help. A sudden fall or movement can twist a joint and can pull or tear a muscle or a ligament. This is called a sprain. A sudden movement or fall may fracture a bone. A fracture is a break or crack in a bone. A doctor needs to fit the broken ends together. A cast keeps the ends in place while bone cells heal the break.