Blood Vessels

Arteries

Vessels that carry blood away from the heart under high pressure. They have thick, muscular, elastic walls and a narrow lumen to withstand high pressure.

Veins

Vessels that carry blood towards the heart under low pressure. They have thinner walls, a wide lumen and valves to prevent the backflow of blood.

Capillaries

Microscopic, one-cell thick vessels that allow exchange of substances (e.g. oxygen, glucose and carbon dioxide) between the blood and tissues by diffusion.

Lumen

The central hole or cavity inside a blood vessel through which blood flows.

Elastic Fibres

Fibres in the artery walls that stretch and recoil to maintain high pressure and smooth out blood flow.