veins/arteries/capillaries

• arteries carry blood away from the heart and blood flow is to the rest of the body
• veins carry blood into the heart - blood flow is from the rest of the body
• blood flows through organs in very tiny blood cells called capillaries. Capillaries are extensive networks so every body cells is near a capillary carrying blood
• its important capillary walls are very thin so blood can pass through easily (shorter diffusion distance)
• coronary arteries supply blood to the heart, muscles, cells
• the blood leaves the heart in arteries, flows through capillaries in the organs and return to the heart via the veins
• pulmonary circulation is to the lungs
• systemic circulation is to the other body organs
• Double circulatory system

  the 4 major blood vessels ;

  A) Vena cava veins

  B) Aorta artery

  C) Pulmonary veins

  D) Pulmonary artery

  E) Lungs

  F) Body

  
• CAPILLARIES 1

  In order to reach every cell, arteries split into smaller vessels called arterioles, then into even smaller capillaries. High pressure at the arteriole, end of capillary bed causes fluid carrying small molecules (e.g glucose, oxygen, water and hormones (not r.b.c's or proteins cause they are too big)) to leak out the capillary walls and washes over the cells bathing them in what is now called tissue fluid.
• CAPILLARIES 2

  Oxygen and dissolved food diffuses across cell membranes into body cells - respiration takes place and waste, CO2 and urea diffuse into tissue fluid. Because of the pressure drop (because of the leaking), fluid drains back into capillaries which rejoin to form larger vessels called venules which turn to join veins and returns blood to the heart
• Capillaries carry out exchange of materials by diffusion

  (Oxygen and CO2)
• VEINS

  • thin muscular wall - allows skeletal muscle to squeeze blood through
  • No pulse - blood flows smoothly
  • Has valves - prevents backflow of blood
  • Large lumen - increases blood flow rate
  • Blood flows slowly at low pressure
• ARTERIES

  • Pulse - pushes blood through the vessel
  • Thick muscular wall - resists high pressure
  • No valves - no need for valves as blood is already under high pressure
  • Smaller lumen - keeps blood at a high pressure
  • Blood flows rapidly at high pressure
• The 'tough outer coat' can also be labelled as the 'Outer layer of tough fibres'

  The vein has a thin muscle layer while the artery has a thick muscle layer

  A) lumen

  B) endothelium

  C) muscle layer

  D) Tough outer coat

  E) Endothelium

  F) Valve