- 3 types of blood vessels:
- Arteries –carry blood away from the heart
- Capillaries – are involved in the exchange of materials
- Veins –carry the blood to the heart
- The heart pumps the blood out at high pressure so the artery walls are strong and elastic.
- The walls are thick compared to its lumen. They contain thick layers of muscles to make them strong.
- Arteries branch into capillaries.
- Very small with very thin walls to allow substances to diffuse in and out of the blood.
- Carry blood close to cells to exchange substances with them.
- One-cell thick walls.
- Capillaries join up to form veins.
- The blood is at lower pressure so the walls don’t need to be as thick as artery walls.
- Bigger lumen to help the blood flow despite lower pressure.
Valves to help keep the blood flowing in the right direction.