Blood vessels and their functions Edexcel AS

Arteries:

• Outer wall contains collagen which makes the outer wall tough
• Thick layer of elastic fibres to allow recoil after high pressure, oushing blood forward
• Narrow lumen to maintain high pressure
• No valves because blood is always being forced forward by heart and elastic recoil of arteries

Veins:

• Outer layer of connective tissue and collagen makes the wall tough
• Thin walls which don't have much elastic fibre or smooth muscle because the blood…