Arteries: carry blood from heart to the rest of the body. They have strong muscular walls.
Veins: carry blood from the rest of the body to the heart. They have elastic walls
Capillaries: allows substances to pass through cells or viceversa. They are very thin
Blood in the arteries is under high pressure generated by the heart. The arteries have:
1.thick outer walls
2. thick layers of muscle and elastic fibres.
The blood in veins is under lower pressure than the blood in arteries. The veins have:
1. thin walls
2. thin layers of muscle and elastic fibres.3. Unlike arteries, veins have one-way valves in them to keep the blood moving in the correct direction.
The function of capillaries is to allow food and oxygen to diffuse to cells while waste is diffused from cells. Capillaries have thin walls - only one cell thick
It transports: nutrients, oxygen, CO2, waste products (urea), hormones, etc.