The lungs are the organs responsible for respiration. Lee-Ellen Copstead, Ph.D. and Jacquelyn Banasik, Ph.D., authors of "Pathophysiology: Biological and Behavioral Perspectives," discuss the respiratory system in depth. The specific anatomy of the lungs and function are reviewed; however, the importance of these organs and their function in relation to life is revealed in the authors' statement that our breathing reveals us; our breathing sustains us. The lungs are truly vital organs.
Bronchial Tree and Alveoli
When people inhale, air moves down the trachea or windpipe. The trachea ends at about the level of the fourth vertebra where it splits into two pipes called the right and left main stem bronchus. Each bronchus provides an air passageway to a lung. According to the American Heart Association, the right bronchus has a shorter, more direct, route to the right lung than does the left bronchus to the left lung. Each bronchus continues to divide into many bronchi, or small pipes, which further divide throughout the lungs into millions of tiny branches called bronchioles. This system of bronchi and bronchioles is referred to as the bronchial tree.
At the end of each bronchiole are small sacs called alveoli. Alveoli are responsible for exchanging oxygen and carbon dioxide. Each alveolus is closely situated to small blood vessels called capillaries. Oxygen and carbon dioxide diffuse across the thin membranes that separate the alveoli and capillaries, bringing oxygen rich blood to the body and removing carbon dioxide from the lungs through exhalation.
The bronchial tubes are lined with very small hair-like structures called cilia. Cilia use a constant wave-like motion to carry mucus up the airway to the throat where it is either swallowed or coughed out. This process helps remove foreign substances and germs from the respiratory system to reduce the risk of infection.
Lobes
The right lung is divided into three sections called lobes. The American Lung Association describes each lung lobe as a balloon filled with sponge-like tissue. This tissue contains the bronchioles, alveoli, and capillaries necessary for oxygenation of the blood. The left lung has only two lobes because of its anatomical position (next to the heart) in the chest cavity. The lungs are separated by the mediastinum, which is the area in the chest cavity that contains the heart, trachea, esophagus and blood vessels.
Pleura
The lungs are surrounded by a membrane called the pleura. This membrane wraps around each lung and helps to separate them from the wall of the chest cavity. A very small amount of fluid is present between the pleural linings. It acts as a lubricant during lung inflation and deflation, easing inspiration and expiration.
Pulmonary Vein and Pulmonary Artery
The pulmonary artery brings de-oxygenated blood (blue blood) from the heart to the lungs. At the level of the capillaries and alveoli, the carbon dioxide is exchanged for oxygen. The oxygenated blood is carried back to the heart by the pulmonary vein.
References
- "Pathophysiology: Biological and Behavioral Perspectives;" Lee-Ellen Copstead, Ph.D. and Jacquelyn Banasik, Ph.D.; 2000
- American Lung Association: How lungs work
- American Heart Association: Advanced cardiac life support
