1. Human heart is four chambered muscular organ. 

2. The size of the heart is about one’s own fist and its weight is about 360 gm. 

3. For protection, it is covered over by doublelayered pericardium. 

4. The wall of the heart is made up of cardiac muscles which are involuntary in nature. They have the capacity of rhythmic beating. 

5. The upper two chambers are called right and left atrium and lower two chambers are called right and left ventricle. 

6. Between right atrium and right ventricle there is tricuspid valve which guards the opening. Similarly between left atrium and left ventricle there is bicuspid valve.

7. On entire right side of the heart there is deoxygenated blood. 

8. On entire left side of the heart there is oxygenated blood. 

9. Right atrium receives deoxygenated blood by superior and inferior vena cava. These two major veins bring deoxygenated blood from entire body to the heart. 

10. Left atrium receives oxygenated blood from lungs by pulmonary vein. 

11. Right ventricle sends the deoxygenated blood to lungs for oxygenation, through pulmonary artery. 

12. Left ventricle supplies oxygenated blood to entire body through systemic aorta.