Human body systems, Year 7: more practice

The skull

提示Think of what covers your head.

为什么The skull is made of fused bones forming a hard case around the brain.

The ribs (rib cage)

提示They curve around the chest.

为什么The rib cage forms a protective cage and moves when you breathe.

The backbone (vertebral column)

提示It is made of many small bones.

为什么The vertebrae have a hole through them where the spinal cord runs. The pads between them let the back bend.

Protection

提示Think of what a cage does for something soft inside it.

为什么The ribs, skull and backbone guard soft organs: the ribs shield the heart and lungs, the skull the brain and the backbone the spinal cord.

Calcium

提示Milk gives you lots of it.

为什么Calcium and phosphate give bone its strength. Bone also contains tough fibres that stop it being brittle.

A tendon

提示It is tough and does not stretch much.

为什么A tendon is a strong cord of tissue. When the muscle contracts it pulls on the bone through the tendon.

A muscle can only pull, so another muscle is needed to pull the bone back

提示Muscles cannot push.

为什么A muscle can only contract and pull. One muscle bends a joint and its partner straightens it again.

The hamstring

提示It is the muscle pair partner.

为什么The quadriceps and hamstring form an antagonistic pair. When one contracts the other relaxes.

It gets shorter (and fatter)

提示Contract means to pull together.

为什么A muscle contracts and shortens, which pulls on the bone it is attached to.

antagonistic

提示The word means working against each other.

为什么The biceps and triceps are an example. When one contracts the other relaxes.