Bone

A bone is a rigid tissue that constitutes part of the skeleton in most vertebrate animals. Bones protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions.

Bone
A bone dating from the Pleistocene Ice Age of an extinct species of elephant
A scanning electronic micrograph of bone at 10,000× magnification
Identifiers
MeSHD001842
TA98A02.0.00.000
TA2366, 377
THH3.01.00.0.00001
FMA5018
Anatomical terminology

Bone tissue (osseous tissue) is a hard tissue, a type of specialized connective tissue. It has a honeycomb-like matrix internally, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells. Osteoblasts and osteocytes are involved in the formation and mineralization of bone; osteoclasts are involved in the resorption of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralized matrix of bone tissue has an organic component of mainly collagen called ossein and an inorganic component of bone mineral made up of various salts. Bone tissue is a mineralized tissue of two types, cortical bone and cancellous bone. Other types of tissue found in bones include bone marrow, endosteum, periosteum, nerves, blood vessels and cartilage.

In the human body at birth, there are approximately 300 bones present; many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small sesamoid bones.[1][2][3] The largest bone in the body is the femur or thigh-bone, and the smallest is the stapes in the middle ear.

The Greek word for bone is ὀστέον ("osteon"), hence the many terms that use it as a prefix—such as osteopathy.