You have 206 bones in your body. In your wrist alone, you have 7 bones. You have 26 vertebras, which are backbones. A mandible is the scientific name for your jawbone, which is part of the bones of your skull. Bones contain marrow, spongy bone, and calcified bone. Marrow makes new blood. Your dogs like bones so much because they like the marrow. Spongy bone is a hard area in the end of your bones. Spongy bone helps your bones not to crutch into pieces. Calcified bone is the hard, white outer layer of your bone, which becomes stronger and longer when you grow. When you break a bone your blood begins to heal it. A callus forms around the broken bone, and holds all of the broken parts of your bones together.