Types of blood vessel

• arteries = big blood vessels that take oxygenated blood to the organs
• capillaries = small, narrow blood vessels inside organs
• capillary network = all cells near to be supplied with oxygen + digested food e.g. glucose
• endothelium = one cell thick -> short diffusion pathway for gas exchange
• veins = deoxygenated (bar 1)
• arteries = oxygenated (bar one)
• vena cava = vein
• muscle layer = contains elastic fibres

  veins also have valves to prevent backflow

  A) tough outer coat

  B) muscle layer

  C) endothelium

  D) lumen

  E) artery

  F) vein

  
• endothelium of capillaries = one cell thick -> short diffusion pathway for gases

  smooth -> less friction -> faster flow of blood
• slow flow = low pressure
• fast flow = high pressure
• arteries have a narrower lumen compared to veins -> helps to maintain the pressure in arteries
• arteries have a thicker muscular wall to contract deeply and to maintain a higher pressure than veins
• veins have a wider lumen compared to arteries
• veins have a thinner muscular wall than arteries as veins do not need to maintain a high pressure