Given below is the diagram of a human heart showing one phase of contraction. Study the same and answer the following questions.

(i) Label the parts numbered as 3 and 4.

(ii) What is the main difference between the blood flowing through the parts numbered as 1 and 2 ?

(iii) Write one important role of the part numbered as 5.

(i) Parts numbered 3 and 4 are:

• 3 → Bicuspid valve
• 4 → Aortic Semilunar valve

(ii) Blood flowing through 1 (Pulmonary artery) is deoxygenated. Blood flowing through 2 (Aorta) is oxygenated.

(iii) Part 5 is pulmonary semilunar valve. It prevents backflow of blood into ventricles.