Bones are alive, active tissues that are continuously being remodeled by the body.
Their duties include bodily structure support, organ protection, and movement of the body. In addition, bone marrow and blood cells are produced in the bones by the body. They also serve as a mineral storage region, especially for calcium.
Bones are made up of two kinds of tissue.
Compact (cortical) bone is a thick, powerful, and long-lasting outer covering. It accounts for approximately 80% of mature bone density and comprises the outer layer of bone.
The remaining 20% of bone is cancellous (trabecular or porous) bone, which is made up of a network of trabeculae, or rod-like structures. It is less thick, lighter, and more pliable than compressed bone.
Bones also contain:
- osteoblasts and osteocytes, responsible for creating bone
- osteoclasts, or bone-resorbing cells
- osteoid, a mix of collagen and other proteins
- inorganic mineral salts within the matrix
- nerves and blood vessels
- bone marrow
- cartilage
- membranes, including the endosteum and periosteum