The human lungs are a pair of cone-shaped, spongy organs located on either side of the chest (thorax). The right lung is slightly larger than the left lung to accommodate the liver lying beneath it.
Each lung is divided into lobes; the right lung has three lobes, while the left lung has two. The lungs are surrounded by a thin layer of tissue called the pleura.
The primary function of the lungs is to take in oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere.
This process of gas exchange occurs in the alveoli, which are tiny air sacs located at the end of the bronchial tree. The alveoli are surrounded by a network of capillaries, through which oxygen and carbon dioxide are exchanged.
The lungs are also responsible for maintaining the body's acid-base balance. Carbon dioxide, a waste product of cellular metabolism, is carried in the bloodstream to the lungs where it is exhaled. Excess acid in the body is also expelled through the lungs in the form of carbon dioxide.
The respiratory system helps to regulate the body's temperature by releasing heat through exhalation. In addition, the lungs play a role in vocalization by providing a route for air to flow over the vocal cords.
The lungs are susceptible to a number of diseases and disorders, the most common of which is pneumonia, an infection of the lungs that can be caused by bacteria, viruses, or fungi. Other respiratory diseases include bronchitis, lung cancer, and tuberculosis.