9-THE LUNGS The lungs are paired organs in the chest that perform respiration. In human, there are two lungs each one is present at one side in the thoracic cavity. The right lung has 3 lobes an 2 fissures, while the left has two lobes and one fissures. المحاضرة الرابعة

Function of lungs against damage: 1.Filtration action of the respiratory passages. 2.Secretion of mucus by mucosa of air passages. It acts as a trap for foreign particles and bacteria. 3.Cough reflex. 4.Sneezing reflex. 5.Moistening of dry air and buffering of excessively hot or cold air. 6.Peristaltic movement of bronchioles driving foreign particles to larger passages. 7.Movement of cilia of respiratory mucosa drives mucus with its trapped particles to the pharynx where it is coughed or expelled.

9.The tonsils have a protective function against bacteria. 10.The presence of a thin layer of fluid between the parietal and visceral layers of pleura acts as a lubricant. 10-The pleura It is a thin double-layered protective serous membrane covering the lungs. 1.The parietal pleura 2.The visceral pleura

The blood supply of the lungs: Lymphatics : The lymphatics of the lung fall into two main divisions : 1.A superficial set : present in the pleura. 2.A deep set : in the pulmonary parenchyma