Human body systems, Year 8: more practice

The oesophagus

HintIt runs through the chest.

The whyMuscles in the wall of the oesophagus squeeze the food down in waves.

To absorb water from the undigested food

HintThink about what is left at the end.

The whyUndigested food moves into the large intestine, where water is absorbed. What is left forms faeces.

A hinge joint

HintIt only bends in one direction.

The whyA hinge joint allows movement backwards and forwards in one plane, like a door hinge.

A ball-and-socket joint

HintThe end of the bone is round.

The whyThe ball-shaped end of the upper arm bone fits into a cup in the shoulder, giving movement in many directions.

Protease

HintIts name suggests what it acts on.

The whyProtease works in the stomach and small intestine. The amino acids can then be absorbed.

They give a large surface area for absorbing food

HintThink about how a bigger lining lets more nutrients cross at once.

The whyVilli are tiny finger-like projections. A larger surface area means more digested food can be absorbed at once.

Diffusion

HintMolecules spread from high to low.

The whyFood molecules diffuse through the thin wall of a villus. The blood carries them away, which keeps the concentration low.

Carbon dioxide

HintIt is a waste gas from respiration.

The whyThe blood in the lung capillaries is high in carbon dioxide, so it diffuses into the alveoli.

So gases only have a short distance to diffuse

HintThink about how far oxygen has to travel to reach the blood.

The whyA thin wall means a quick diffusion of oxygen into the blood and carbon dioxide out of it.

They make it by photosynthesis

HintPlants do not eat.

The whyPlants make glucose from carbon dioxide and water using light, then respire it to release energy.

Your muscles need more oxygen for respiration, and more carbon dioxide must be removed

HintThink about what working tissues use up and what they give off.

The whyMore respiration in the muscles uses oxygen faster and makes more carbon dioxide.

Arteries

HintThey have thick, muscular walls.

The whyArteries carry blood at high pressure away from the heart. Veins return it.

The ribs move down and in, and the diaphragm relaxes and moves up

HintThe opposite of breathing in.

The whyThe chest volume goes down and the pressure rises, so air is pushed out.

Respiration

HintOne happens in the lungs and one in the cells.

The whyBreathing moves air into and out of the lungs. Respiration happens in cells and releases energy from glucose.