CBSE Class 10 Answered

The circulatory system consists of heart, blood vessels i.e arteries, veins and capillaries, bloodand lymph. Platelets are important to clot the blood at points of injury.

Mechanism of Transport of Blood

Blood is constantly pumped by the heart, through the blood vessels to the various parts of the body and from there back to the heart. This process is called circulation of blood.

When heart relaxes, oxygenated blood enters the left atrium  through the pulmonary veins. At the same time, deoxygenated blood is brought into the right atrium by the precavals and post caval. When the atria contract, oxygenated blood from the left atrium enters the left ventricle and deoxygenated blood from the right atrium enters the right ventricle. Immediately after this, the ventricles contract. Oxygenated blood from the left ventricle is carried by the aorta and through its branches, it is supplied to all the parts of the body. The right ventricle pumps deoxygenated bloood through the pulmonary artery towards the lungs for oxygenation. The deoxygenated blood gets oxygenated in the lungs and is brought to the left atrium. This blood gets deoxygenated as it flows through the different parts of the body and is brought back to the right atrium. Thus the blood passes twice through the heart.