CogKnoSys

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Physical

Bone Growth

Bone growth, called ossification, is the process in which cells named osteoblasts lay down new bone tissue.

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The idea

Bones are living tissue, and they are built by a process called ossification. Special cells called osteoblasts lay down new bone material, layer by layer. The same process keeps working throughout life as the body remodels old bone and repairs damage.

Healthy bone forms in two main ways. In intramembranous ossification, bone is laid down directly into soft connective tissue. In endochondral ossification, the body first builds a model out of cartilage, and bone then replaces it. A third, less studied form lets bone spread into the membranes around the original cartilage.

The same processes heal broken bones. A long bone set in a plaster cast usually heals through the cartilage route, while a break held together with metal plates and screws may heal by direct bone growth. Ossification is often confused with calcification, which is the build-up of calcium salts and crystals in tissue. Calcification happens during ossification, but it can also happen without any bone forming.

Check yourself

Question 1 of 2

Which cells lay down new bone material?

Pick one. The first pick counts.

Composition

what it's made of

  • Osteoblasts — The cells that lay down new bone material.
  • Intramembranous ossification — Bone laid down directly into soft connective tissue.
  • Endochondral ossification — Bone that replaces an earlier cartilage model.
  • Calcification — The forming of calcium salts and crystals, a step that happens during ossification.
  • Growth signals — Growth factors and cytokines that appear to help trigger bone development.

Connection

how it relates

Under Skeletal System

Related

  1. Skeletal Musclestrength 60 of 100

    Skeletal muscles pull on bones through tendons, so strong bones and muscles work as a team.

  2. Metals and Alloysstrength 40 of 100

    Doctors sometimes hold broken bones together with metal plates, screws and rods while new bone grows.

  3. Muscle Contractionstrength 40 of 100

    Bones act as levers that contracting muscles pull to move the body.

Change

how and why it evolves

Past
In a growing child, much of the skeleton starts out as cartilage that is later replaced by bone through endochondral ossification.
Now
Doctors rely on ossification every time a broken bone heals, whether it is set in a cast or fixed with metal hardware.
Next
Exactly what triggers bone development is still unclear, so future research on growth factors and cytokines may lead to better treatments for bone injuries.

Knowledge you can walk. Read the idea, then step up, across or down.

Bone Growth

Bone growth, called ossification, is the process in which cells named osteoblasts lay down new bone tissue.

Learn, discuss, create, buy or invest

The idea

Bones are living tissue, and they are built by a process called ossification. Special cells called osteoblasts lay down new bone material, layer by layer. The same process keeps working throughout life as the body remodels old bone and repairs damage.

Healthy bone forms in two main ways. In intramembranous ossification, bone is laid down directly into soft connective tissue. In endochondral ossification, the body first builds a model out of cartilage, and bone then replaces it. A third, less studied form lets bone spread into the membranes around the original cartilage.

The same processes heal broken bones. A long bone set in a plaster cast usually heals through the cartilage route, while a break held together with metal plates and screws may heal by direct bone growth. Ossification is often confused with calcification, which is the build-up of calcium salts and crystals in tissue. Calcification happens during ossification, but it can also happen without any bone forming.

Check yourself

2 quick questions, instant feedback.