A cage that moves

The idea

The rib cage, 12 pairs of ribs joined to the spine and sternum by flexible cartilage, protects the heart and lungs; its flexibility lets it expand and contract in breathing, moving air in and out of the lungs.

Feel your ribs

Place your hands on your chest and breathe in deeply. You can feel your chest move.

A cage of bones protects the heart and lungs. How can it move when you breathe?

• Its joints are flexible
• It cannot move at all
• It is soft like a sponge

Expand and contract

Move the slider to expand and contract the rib cage.

Flexible cartilage

The ribs are attached to the spine at the back and to the breast bone in front, and flexible cartilage joins them. This flexibility lets the rib cage expand and contract. The space in the chest changes, and air moves in and out of the lungs.

The rib cage, 12 pairs of ribs joined to the spine and sternum by flexible cartilage, protects the heart and lungs; its flexibility lets it expand and contract in breathing, moving air in and out of the lungs.

Notes

The rib cage (12 pairs of ribs, joined by flexible cartilage) protects the heart and lungs and expands and contracts as we breathe.

Check yourself

Which organs does the rib cage protect?

How many pairs of ribs do we have?

Answer: 12

We have 12 pairs of ribs, and together they form the rib cage.

What joins the ribs to the sternum in front, and lets the rib cage move?

What happens in the chest when the rib cage expands and contracts?

• The brain and ears. The skull protects the brain, eyes and ears.
• The heart and lungs — correct. Yes!
• The spinal cord. The rib cage acts like a protective cage for vital organs such as the heart and lungs.
• Hard, rigid bone. Bone is rigid. It is the flexible cartilage that lets the rib cage expand and contract.
• Fixed joints. Fixed joints allow no movement. The rib cage needs to expand and contract, so it is joined by flexible cartilage.
• Flexible cartilage — correct. Yes!
• The space in the chest increases and decreases, so air moves in and out of the lungs — correct. Yes!
• The lungs are pulled out of the chest. The lungs stay inside the rib cage. The space in the chest changes, and air moves in and out.
• The heart is squeezed out of the cage. The rib cage protects the heart. Its movement changes the space in the chest so that air moves in and out of the lungs.