Junior Class 5 Answered

Respiration is the primary function of the lungs. Their primary function is to transport oxygen from the environment into the bloodstream and to expel carbon dioxide from the bloodstream into the environment. This gas exchange takes place in alveoli, which are thin-walled air sacs.The lungs also play an important role in the body's defence against infection and other potentially harmful environmental factors. The lungs serve as the body's second line of defence. Inhaled particles or infectious agents such as bacteria and viruses enter the lungs through the mouth or nose. Mucus, a sticky fluid produced in the lungs, can trap these inhaled agents and help the lungs' protective white blood cells (macrophages and neutrophils) engulf and destroy bacteria and other harmful materials.