heart is an muscular organs which pumps blood around the whole parts and body tissues through a vasculature which is made up of 4 chambers and valves with a septum the 2 AV valves and 2 semilunar valves . 
  - oxygenated blood leaves lungs then it reaches to LV of the heart through pulmonary veins , 
  - LA squeezes the oxygenated blood to lungs then it pumped by LV to the all tissues of the body .
  - aorta branches to form arteries that carry to various tissues and it is terminated in capillaries 
   - capillaries helps to exchange oxygen and carbondioxide and join to form veins .
  - veins from tissues forms superior and inferior vena cava .
  - the vena cava pour blood into RA . 
  - RA squeezes blood into RV . 
   - then lungs capillaries helps to exchange carbondioxide with oxygen .