CBSE Class 10 Science 2019 · Paper 31/3/1 · Question 9

Four functions of the human heart: (i) Its right atrium receives deoxygenated blood from the body (through the vena cava). (ii) Its right ventricle pumps this deoxygenated blood to the lungs for oxygenation (through the pulmonary artery). (iii) Its left atrium receives oxygenated blood from the lungs (through the pulmonary veins). (iv) Its left ventricle pumps the oxygenated blood to all parts of the body (through the aorta). Double circulation is necessary because it keeps oxygenated and deoxygenated blood separate: blood passes through the heart twice in each round, once to go to the lungs and once to go to the body. This gives a highly efficient supply of oxygen to the body, which humans need because of their high energy needs; they constantly use energy to maintain their body temperature.