blood vessels

• arteries carry blood away from the heart
• capillaries exchange nutrients and oxygen with tissues
• veins carry the blood back to the heart
• arteries blood will be at a high pressure due to to just being pumped out from ventricles.
• arteries are string and elastic to withstand strong pressure of blood
• arteries have a thick layer of muscle and elastic tissue
• the wall of the artery is thick
• the lumen is the space in the middle of a vessel
• the capillaries are very small
• the capillaries exchange nutrients and oxygen with cells
• the capillaries take away co2 waste
• the capillaries lumen is very small
• the cross section of capillaries is huge
• huge cross section of capilaries means that it has a lower blood pressure
• the capillaries flow slowly giving the blood more time to exchange with the tissues
• capillaries start to join up into larger vessels called veins
• veins have the biggest lumen out of all the blood vessels
• the walls of veins dont need to be strong since they cally low pressure blood
• veins have valves to prevent backflow of blood when going to the heart
• to calculate blood flow its = blood flow divided by the time taken

  A) calculate blood flow
• arteries have a narrow lumen which keeps blood pressure high
• capillary walls are permeable so substances can pass through quickly
• capillaries are a single cell thick so diffusion can happen easily
• amino acids and glucose are nutrients the capillaries give to cells
• co2 and urea are waste products
• glucose and amino acids are nutrients
• permeable means substances can easily diffuse through them