The light pink colored large and soft organ like sponge in human chest is called lung. Human body has two lungs. Right and left lung. The two lungs together weigh 2.9 pounds. The right lung is large and weighs 625 grams. It is divided into three lobes by horizontal fissure and oblique fissure. Superior lobe, middle lobe and inferior lobe. Left lung small weight 565 grams. It is divided into two lobes by the oblique fissure. Superior Lobe and Inferior Lobe. There are 10 lobules in the right lung and 8 in the left lung. Each lobule is composed of alveoli. The space through which the bronchi, blood vessels and lymphatic channels enter the lungs is called Alveoli. The bronchi, blood vessels and alveolar ducts are surrounded by connective tissue and form the root of the lungs.
Each lung is covered by a two-layered thin membrane called Pleura. The outer layer is called Parietal and the inner layer is called Visceral layer. Serous fluid is between the two layers. Serous fluid protects the lungs from frictional injury.
