A quick bone anatomy lesson.

Human bones are made up of several layers and components, each with a specific function that contributes to the overall strength and structure of the bone.

The outermost layer of a bone is called the periosteum. This layer is a tough, fibrous membrane that covers the entire bone, except for the areas where it articulates with other bones. It contains blood vessels, nerves, and lymphatic vessels that supply nutrients to the bone tissue.

Beneath the periosteum lies compact bone, which is the hard, dense outer layer of the bone. This layer provides the bone with strength and protection. Compact bone is composed of a matrix of calcium salts and collagen fibers arranged in a pattern called the Haversian system. This system consists of small, cylindrical units called osteons or Haversian canals, which contain blood vessels and nerves.

Inside the compact bone lies the spongy or cancellous bone. Spongy bone is composed of a lattice-like network of thin, needle-like pieces of bone called trabeculae. These trabeculae are arranged in a way that provides maximum strength with minimum weight. Spongy bone is found mainly in the ends of long bones, such as the femur (thigh bone) and humerus (upper arm bone), and in the vertebrae of the spine.

At the very center of the bone lies the bone marrow, which is a soft, spongy tissue that produces blood cells and stores fat.