I can explain..!!heart is an organ which beats continuously to act as a pump which transport blood and other substances with it.heart transports blood with oxygen to all parts of the body through arteries except the pulmonary artery.it collects back blood rich in carbondioxide from all parts of the body through vein except the pulmonary vein.the rhythemathic beating of various chambers of the heart maintains the circulation of the blood and transportation of substances like nutrients, oxygen,carbondioxide and other waste products.the blood flow from heart to lungs and back to heart from where it pumps to rest of the body..!! :)) ok?

Our heart function. Dear it is a very big topic. To understand this please read chapter 11 of science book for class 7. There u will know for sure. Hope this helps!