Explain working of human heart in …

* It is a four chambered structure consisting - the right auricle , the left auricle , right ventricle and left ventricle.

* The Auricles are smaller and placed above the ventricles. Auricles are partitioned by a muscular called septum.

* The right auricle receives the deoxygenated blood from all parts of the body except the lungs. It pumps this blood into the right ventricle. Then , the right ventricle pumps the deoxygenated blood to the lungs. The left auricle receives oxygenated blood from the lungs through pulmonary veins. It pumps this blood into the left ventricle. The left ventricle pumps the oxygenated blood to the distant organs in the body.

* Each auricle communicates with the ventricle of its side by a pore which is guarded by valves. These valves allow the blood to flow from the auricles to the ventricles but check its return to the auricles. Thus , the heart there is a complete separation of oxygenated and deoxygenated blood. The heart is enclosed in a double membrane called pericardium. It contains fluid which protects the heart from any shock or mechanical injury.

*The heart collects blood through both the auricles and then distributes it through ventricles. The action of heart includes contraction and relaxation of the auricles and ventricles.

* A contraction of heart is called systole and diastole. The contraction and relaxation occur in an automatic rhythmic fashion. The auricles and ventricles contract alternately. The rhythmic contraction and relaxation of heart is called a heart beat.