GCSE Biology: Blood Vessels

Veins

Arteries

Capillaries

The left ventrical is larger than the right ventrical because the left ventrical pumps to the entire body yet the right ventrical pumps to the only the lungs and so does not need to be as strong.

The right atrium is bigger than the left because more blood gos into the right atrium than the left. It comes from the entire body instead just the lungs and so there is more blood.

Arteries have more muscle in the wall than veins because they have to cope with blood at a higher pressure than the veins. Arteries have blood at high pressure coming through them. If they were designed as veins are they would split.

Capillaries have very thin walls to allow transfer of gases and other materials. They have a large surface area and are perfectly constructed for blood transfusions.

Veins contain valves so that blood cannot flow backwards. They make sure blood flows only the correct way back to the heart.