The lungs are two spongy organs located in the chest, responsible for gas exchange. They are divided into lobes: the right lung has three lobes, while the left lung has two lobes to accommodate the heart. Each lung is surrounded by a protective membrane called the pleura. Air enters the lungs through the trachea, which branches into smaller tubes called bronchi. These bronchi further divide into even smaller passages known as bronchioles, leading to tiny air sacs called alveoli. The alveoli are where oxygen is absorbed into the blood, and carbon dioxide is expelled.