Structure and function of blood vessels

• Arterioles branch into capillaries which form networks in tissues called capillary beds
• Once exchange has occurred, deoxygenated blood flows from capillaries into venules, these then join to form veins and blood is transported back to the heart
• Arteries, arterioles and veins:

  Smooth muscle layer - Contracts to control the flow of blood
• Arteries, arterioles and veins:

  Elastic layer - Helps to maintain blood pressure by stretching and springing back (Recoiling)
• Arteries, arterioles and veins:

  Endothelium - Thin inner lining which is smooth to reduce friction and thin to allow diffusion
• Lumen - The central cavity of the blood vessel through which the blood flows