Bone

A bone is a <a href="/facts/Stiffness/xlabLkfT">rigid</a> <a href="/facts/Organ_(biology)/FUYsLaxz">organ</a> that constitutes part of the <a href="/facts/Skeleton/FXc9Y2lF">skeleton</a> in most <a href="/facts/Vertebrate/tT54FSTT">vertebrate</a> animals. Bones protect the various other organs of the body, produce <a href="/facts/Red_blood_cell/Kggpq8Jh">red</a> and <a href="/facts/White_blood_cell/vsDunUK0">white blood cells</a>, store <a href="/facts/Mineral/LkUFbNmv">minerals</a>, provide structure and support for the body, and enable <a href="/facts/Animal_locomotion/trhhYTVR">mobility</a>. Bones come in a variety of shapes and sizes and have complex internal and external structures. They are lightweight yet strong and hard and serve multiple <a href="/facts/Function_(biology)/a5hLtnS7">functions</a>.
Bone tissue (osseous tissue), which is also called bone in the <a href="/facts/Mass_noun/Vor8JWmL">uncountable</a> sense of that word, is <a href="/facts/Hard_tissue/VDkazYh5">hard tissue</a>, a type of specialised <a href="/facts/Connective_tissue/mal3fc7k">connective tissue</a>. It has a <a href="/facts/Honeycomb/oeAFHaxm">honeycomb</a>-like <a href="/facts/Matrix_(biology)/up2ogMb7">matrix</a> internally, which helps to give the bone rigidity. Bone tissue is made up of different types of <a href="/facts/Bone_cell/nUBl8e1S">bone cells</a>. <a href="/facts/Osteoblast/N6mMDQvR">Osteoblasts</a> and <a href="/facts/Osteocyte/nUBl8e1S">osteocytes</a> are involved in the formation and <a href="/facts/Mineralization_(biology)/m5mGPaTM">mineralisation</a> of bone; <a href="/facts/Osteoclast/jHHtEQru">osteoclasts</a> are involved in the <a href="/facts/Bone_resorption/cMx23mGW">resorption</a> of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralised matrix of bone tissue has an organic component of mainly <a href="/facts/Collagen/KsyAb72K">collagen</a> called <a href="/facts/Ossein/6wgRvpms">ossein</a> and an inorganic component of <a href="/facts/Bone_mineral/L6LpbEYE">bone mineral</a> made up of various salts. Bone tissue is <a href="/facts/Mineralized_tissues/N7j1X52h">mineralized tissue</a> of two types, cortical bone and cancellous bone. Other types of tissue found in bones include <a href="/facts/Bone_marrow/4dfudk0H">bone marrow</a>, <a href="/facts/Endosteum/amC7gAlf">endosteum</a>, <a href="/facts/Periosteum/vRlYlFgQ">periosteum</a>, <a href="/facts/Nerve/q7GsAfYV">nerves</a>, <a href="/facts/Blood_vessel/FG3GjPNW">blood vessels</a>, and <a href="/facts/Cartilage/vxy2qzKN">cartilage</a>.
In the <a href="/facts/Human_body/WP1QbDTn">human body</a> at birth, approximately 300 bones are present. Many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small <a href="/facts/Sesamoid_bone/q9uWpHKS">sesamoid bones</a>. The largest bone in the body is the <a href="/facts/Femur/uVyTwj4l">femur</a> or thigh-bone, and the smallest is the <a href="/facts/Stapes/TbLLQTrw">stapes</a> in the <a href="/facts/Middle_ear/H2A50utA">middle ear</a>.
The <a href="/facts/Ancient_Greek/LIK7NlUh">Ancient Greek</a> word for bone is ὀστέον ("osteon"), hence the many terms that use it as a prefix—such as <a href="/facts/Osteopathy/BrS9UGbh">osteopathy</a>. In <a href="/facts/Anatomical_terminology/n3IASQlr">anatomical terminology</a>, including the <a href="/facts/Terminologia_Anatomica/m4qt6jop">Terminologia Anatomica</a> international standard, the word for a bone is os (for example, <a href="/facts/Short_bone/VKIMzNat">os breve</a>, <a href="/facts/Long_bone/hKScebY6">os longum</a>, <a href="/facts/Sesamoid_bone/q9uWpHKS">os sesamoideum</a>).

Bone open-in-new

Bone