Blood Vessels

• Arteries carry blood away from the heart and have thick muscular walls to withstand high pressure
• Capillaries exchange materials at the tissues
• Veins carry blood to the heart at a lower pressure than arteries.
• Artery walls are strong and elastic to withstand the high pressure of blood flowing through them
• Artery walls are thick compared to the lumen to withstand the high pressure of blood
• Capillaries have a wall one cell thick to increase the rate of diffusion by decreasing the distance the substance has to travel
• Blood in the veins has low pressure so the walls don't have to be as thick as artery walls
• Veins have a bigger lumen than arteries, so they can carry more blood despite the low pressure
• Veins have valves to prevent backflow of blood and a thick muscular wall to withstand high pressure
• Arteries have thick walls to prevent damage to the lumen from the pressure, to stop it from bursting
• The ventricles are the lower chambers of the heart that pump blood into the aorta
• Lumen


  The inner cavity or space within a tube or tubular organ, such as a blood vessel
• Blood pressure


  The force that blood exerts on the walls of the blood vessels
• Veins

  Blood vessels that carry blood towards the heart
• Arteries


  Blood vessels that carry blood away from the heart
• Lumen size


  The size of the inner cavity or space within a tube or tubular organ, such as a blood vessel
• Vessel walls

  The thicker and more rigid the walls of a blood vessel, the smaller the lumen
• Blood pressure

  The pressure within a blood vessel can affect lumen size; if the pressure is increased, the lumen may dilate, and if the pressure is decreased, the lumen may constrict
• Thick muscular walls of arteries


  Help to keep the arteries strong and flexible, allowing them to withstand high pressure and continue to transport blood efficiently
• Arteries


  Blood vessels that carry blood away from the heart; have thick muscular walls to withstand high pressure
• Thick walls of arteries

  Help to keep the arteries strong and flexible, allowing them to withstand high pressure and continue to transport blood efficiently; regulate blood flow and maintain blood pressure within a normal range
• The blood transports oxygen from the lungs to all the cells in the body.
• Blood has a biconcave shape to maximise surface area : volume area ratio for absorbing and releasing oxygen
• Blood has no nucleus to maximise space for haemoglobin (what gives blood its colour)
• Blood is very small so it is flexible to easily pass through capillaries.
• Blood contains liquid plasma, this carries everything that the body transports round the body eg urea, hormones, water