Bone
Say it: BOHN
Bone is the hard, mineralized connective tissue that makes up most of the adult skeleton, and the name for each skeletal organ built from it.
Also: bones, osseous tissue
Definition
What is bone?
Bone, or osseous tissue, is a living connective tissue made hard by minerals. Its matrix pairs collagen fibers, which give it a little flexibility, with crystals of hydroxyapatite, a calcium phosphate mineral that gives it rigidity. Each bone in the skeleton is an organ in its own right, with marrow, blood vessels, nerves and a tough outer membrane called the periosteum.
Four kinds of cell keep bone working. Osteogenic cells are stem cells that turn into osteoblasts, which lay down new matrix. Osteoblasts that become trapped in that matrix mature into osteocytes, which maintain it, while large osteoclasts dissolve old bone. This constant remodeling lets bone mend fractures, adapt to the loads placed on it, and release calcium and phosphate into the blood when levels fall.
Bone tissue comes in two forms. Compact bone is dense and built from cylindrical units called osteons, while spongy bone is a light lattice of struts called trabeculae, whose spaces can hold the red marrow that makes blood cells. Together they support the body, shield organs such as the brain and heart, and act as levers that muscles pull on.
Word parts
Where does the word “bone” come from?
- osteo-
- bone; used in medical words such as osteocyte and osteoporosisGreek osteon
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Terms that go with it
- CartilageCartilage is a tough, flexible connective tissue without blood vessels that cushions joints and shapes the nose, ears and airways.
- LigamentA ligament is a band of tough, fibrous connective tissue that joins one bone to another and keeps a joint stable while letting it move.
- TendonA tendon is a tough cord of dense connective tissue linking a muscle to a bone, which passes on the muscle's pull to move it.
- Skeletal muscleSkeletal muscle is the striated, voluntary muscle tissue attached to bones by tendons that moves the body, holds posture and produces heat.
- Red blood cellA red blood cell, or erythrocyte, is a disc-shaped blood cell without a nucleus that is packed with hemoglobin and carries oxygen around the body.
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Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Anatomy and Physiology 2e, 6.1 The Functions of the Skeletal System
- OpenStax Anatomy and Physiology 2e, 6.3 Bone Structure
- NCBI MeSH: Bone and Bones
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