arteries ,veins and capillaries

• tunica externa


  what is the yellow section called

  
• tunica intima


  what is the red section called

  
• tunica media


  what is the red section called

  
• endothelium


  what does the tunica intima consist of
• elastic fibres and smooth muscle


  what does the tunica media consist of
• collagen fibres


  what is the tunica externa made of
• 10mm


  what is the diameter of the whole artery
• 7mm


  what is the diameter of the whole vein
• 5-10um


  what is the diameter of the whole capillary
• they can carry larger volumes of blood

  what is advantage of a veins larger lumen
• the blood above the valve will try to flow back , the blood fills the pockets and the valves are forced shut


  describe how valves work
• gravity will draw the blood down towards the heart


  why do veins in the heart have no valves