Hey, everyone! It’s Matt from Kenhub, and this tutorial features the most well-known feature of the respiratory system, the lungs.
The lungs are made of a light and soft elastic tissue. The right lung is larger than the left one and is comprised of the 3 lobes including the superior, middle, and inferior. The left lung only has 2 lobes, which are the superior and inferior. Fissures help separate the lobes and each lung has an oblique fissure which divides the upper and lower lobes of the left lung and the middle and lower lobes of the right lung. The right lung also has a horizontal fissure which separates the superior and the middle lobes. Each lung also has 3 surfaces: the costal, the mediastinal, and the diaphragmatic, which are named after the adjacent anatomical structure which that surface faces. The mediastinal surface connects the lungs to the mediastinum via its root. The root of the lung contains the mainstem or lobar bronchi, the pulmonary vessels and bronchi, as well as the bronchiole vessels, lymphatics and autonomic nerves.
The respiratory airways and the lungs are lined with respiratory epithelium. Let’s review the path of respiration for clarification. Once the air enters the larynx, it is purely within the respiratory organs. It continues down the larynx and into the trachea which bifurcates into the left and right main bronchi and then further in a tree branch-like pattern into bronchioles. The bronchioles further divide into smaller and smaller respiratory bronchioles whose terminal branches contain grape-like bunches of alveolar ducts, sacs and the terminal alveoli. It is here that the oxygen in the air cells diffuses into the blood. The opposite occurs for the carbon dioxide when it attempts to leave the hemoglobin molecules in the erythrocytes and travel back out of the body via exhalation.