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Biology · Glossary

What is Skeleton and bones?

Also known as: skeleton · bone · skull · spine · rib

Definition 17.1 Primary & Middle School Biology · Chapter 17 — Bones and Muscles

The skeleton is the frame of about 200200 bones inside the body. Its main regions:

  • the skull, a solid helmet of bone around the brain;
  • the spine (backbone), a bendable column of small bones stacked from neck to hips, holding the trunk upright;
  • the ribs, curved bones forming a cage around heart and lungs;
  • the limb bones: long bones in arms and legs — the thigh bone is the longest of the body.
The skeleton’s plan: helmet, column, cage, and long limb bones meeting at joints.
The skeleton’s plan: helmet, column, cage, and long limb bones meeting at joints.
Inside the decorated cast, held still, a living bone is quietly rebuilding itself.
Inside the decorated cast, held still, a living bone is quietly rebuilding itself.

Examples

Example 17.2 (Feel your frame)

No X-ray needed: press gently and the skeleton reports. Knuckles; the ridge of the shin; the chain of small bumps down the middle of your back — the spine, one small bone after another; the ribs you can count under your fingers. The frame is right under the skin.

Example 17.5 (The spine’s trick)

No single bone in your back can curl — yet you can roll forward almost into a ball. The spine is a column of more than 2020 small bones, each turning a few degrees on its neighbors: many small bends making one big one. That is also why you should bend knees, not back, to lift something heavy — knees are built for big folds, the spine for gentle ones.

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