Purification of blood:
Lungs help in the purification of blood. Arteries carry pure oxygenated blood from the heart to other parts of the body. Veins carry impure venous blood back from other parts of the body to the right side of the heart. This impure blood goes to the lungs for purification.
When breath is inhaled, oxygen from the air comes in contact with the impure blood and the blood takes up oxygen. The waste matter in the blood releases carbonic acid and the blood is purified. The purified blood is carried to the heart by the veins.
In asthma, the bronchial tubes become spasmodic and they contract. This causes difficulty in breathing. Yogic exercises remove the constriction of these tubes.