VMBO Year 3 · Support and movement · Section 5.1
The human skeleton
What is the skeleton for?
Your skeleton is the supporting framework giving your body strength and shape. An adult skeleton usually contains 206 bones. It also protects organs and enables movement: the rib cage protects the heart and lungs, while bones in the limbs act as levers for muscles.
Divisions of the skeleton
For this course, the skeleton is described in three regions: head, trunk and limbs. The head includes the skull bones. The trunk region includes the vertebral column and rib cage, with the shoulder girdle and pelvic girdle linking the limbs to the body. Arms and legs contain bones specialised for movement and support.
Four main functions
- Support: keeping the body upright and resisting forces.
- Shape: providing the body's framework.
- Protection: surrounding vulnerable organs such as the brain, heart and lungs.
- Movement: working with muscles and joints.
Many bones meet at movable joints. Muscles pull on bones to produce movement.
Long bones
Long bones, such as the femur and tibia, have a shaft and enlarged ends. The shaft contains a marrow cavity, often filled with yellow marrow, which stores fat. Spongy bone in the ends can contain red marrow, producing blood cells. Marrow distribution changes with age; in adults, active red marrow is concentrated mainly in parts of the trunk and the upper ends of certain long bones.
Flat bones
Flat bones, including skull bones, ribs and the sternum, often protect organs and provide muscle attachment. They contain spongy bone between layers of compact bone. Several are important sites of red marrow. Long and flat bones are two groups studied here; other bone shapes also occur.
Glossary
- Pelvic girdle
- The hip bones connecting the lower limbs to the axial skeleton.
- Rib cage
- The thoracic vertebrae, ribs and sternum, surrounding organs in the chest.
- Bone
- A living organ forming part of the skeletal system.
- Yellow marrow
- Fat-rich tissue found especially in the marrow cavities of long bones.
- Limbs
- The arms and legs.
- Marrow cavity
- The cavity within the shaft of a long bone.
- Long bone
- An elongated bone with a shaft, enlarged ends and a marrow cavity.
- Flat bone
- A relatively broad, thin bone, often protecting organs and containing spongy bone and marrow.
- Red marrow
- Tissue producing blood cells, found especially in flat bones and certain long-bone ends.
- Shoulder girdle
- The shoulder blades and collarbones linking the upper limbs to the body.
- Skeleton
- The body's supporting framework of bones and associated structures.
Frequently asked questions
What are the skeleton's main functions?
It supports and shapes the body, protects vulnerable organs and makes movement possible together with muscles.
What are human limbs?
The limbs are the arms and legs. Their bones work with joints and muscles to enable movement.
How do long bones differ from flat bones?
Long bones, such as the femur, have an elongated shaft and marrow cavity. Flat bones, such as ribs and skull bones, are broader and thinner, often protect organs and can contain red marrow.