What are the Characteristics of Bones?

The word skeleton comes from the Greek words meaning "a dried body." This suggests that a skeleton is dead, but bones are not dead at all. Bones are complex living structures that grow, develop, and repair themselves. Bones are also strong and lightweight.

Bones are made up of bone tissue, blood vessels, and nerves. A thin, tough outer membrane covers all fo a typical bone except the ends. Beneath the membrane is a thick layer of compact bone, which is hard and dense but not solid. Compact bone contains minerals that give bones strength. Small canals in the compact bone carry blood vessels and nerves from the bone's surface to its living cells.

Long bones, such as the femur, have a layer of spongy bone at the ends and under the compact bone. The small spaces withing spongy bone make it lightweight but still strong. Bone also has two types of soft connective tissue called marrow. Red bone marrow fills the spaces in some of your spongy bone. It produces most of your blood cells. Yellow bone marrow is found in a space in the middle of the bone. It stores fat.