1Four jobs
An adult skeleton has about 206 bones. It supports the body, protects soft organs, lets you move (with muscles), and makes blood cells in the bone marrow.
skeletonsupportprotectionmovement
Lesson 13.1 notes
The skeleton
The skeleton's four jobs, the main bones, what is inside a bone, and what makes bones strong.
2The main bones
Learn the main bones: the skull, collarbone, sternum, ribs and spine; the humerus, radius and ulna in the arm; the pelvis; and the femur, kneecap, tibia and fibula in the leg.
skullvertebraefemur
3Protection
Hard bones guard soft organs. The skull protects the brain, the ribs protect the heart and lungs, and the vertebrae of the spine protect the spinal cord.
skullribsvertebraespinal cord
4Support and movement
The skeleton is a strong frame that holds you up and gives you shape. Muscles pull on bones, and the bones move where they meet, at joints.
supportjoint
5Inside a bone
Hard compact bone forms the outside. The ends are spongy bone, strong but light, filled with red bone marrow. Yellow bone marrow, mostly fat, fills the middle. Cartilage covers the ends.
compact bonespongy bonebone marrowcartilage
6Making blood cells
Red bone marrow makes millions of new blood cells every second: red blood cells carry oxygen, white blood cells fight infection, and platelets (fragments of cells) help blood to clot.
red bone marrowred blood cellswhite blood cellsplatelets
7What makes bone strong
Bone is made of hard calcium minerals and tough, flexible collagen. Soaked in vinegar, the calcium dissolves and the bone bends. Heated strongly, the collagen is lost and it snaps.
calciumcollagen
Explore: Skeleton explorer
Pick a job to see which bones do it, or pick a bone to find it and see what it does.
Common mistake: Bones are alive
A skeleton in a museum is dry and dead, but the bones inside you are living organs. They have blood vessels and cells, they grow, they make blood cells, and they mend when they break.
Remember
- The skeleton's four jobs: support, protection, movement and making blood cells.
- The skull protects the brain, the ribs protect the heart and lungs, and the vertebrae protect the spinal cord.
- Red bone marrow makes blood cells. Calcium minerals make bone hard; collagen makes it tough.
Going further at GCSE