The lungs are two cone-shaped organs that lie on each side of the chest cavity. Thousands of tiny sponge-like air sacs called alveoli make up the lung tissue. This tissue fills the spaces between a network of branching, tree-like tubes and blood vessels in the lungs. The structures of the lungs play a role in many vital body processes.
Function
Lung function includes oxygen uptake and the release of carbon dioxide necessary for respiration. Another vital function of the lungs is to filter out harmful inhaled substances and help prevent infection. It does this through the production of mucus which traps foreign substances. The mucus is then propelled up through the lungs by tiny hair-like filaments called cilia. Coughing moves the mucus out of the body.
Structures
Lung function begins in the main airway, called the trachea, which divides into two main branches called bronchi. One bronchus extends into the right lung and the other into the left lung. The right lung has an upper, middle and lower lobe. A branch of the main bronchus extends to each lobe. The lobes subdivide into segments, each supplied by a segmental bronchus. Each lobe contains thousands of tiny bubble-like structures called alveoli, where the exchange of oxygen and carbon dioxide occurs. The left lung has an upper and lower lobe; each is supplied by a main stem bronchus. The lobes further subdivide into segments, each supplied by a segmental bronchus.
Process
The exchange of oxygen and carbon dioxide occurs in the alveoli. Gases tend to pass from areas of high concentration to areas of lower concentration. As oxygen passes out of the alveoli, and into the capillaries, it enters the red blood cells and binds to hemoglobin, which carries it throughout the body. For the same reason, the systemic carbon dioxide which is highly concentrated, pases out of the plasma in the capillaries into the alveoli so it can be released into the atmosphere when you exhale.
Location
Located in the center of the chest is a depression called a hilus. This is where the blood vessels connect the lungs to the heart, the main bronchi to the trachea, and where connective tissue holds everything in place. The mediastinum is the middle of the chest cavity, located between the lungs. This area contains the heart, the major blood vessels, esophagus, nerves and the connective tissue that holds it all in place.The rib cage surrounds the chest cavity. It consists of 12 pairs of ribs, beginning with the sternum, or breastbone, and the cartilage that connects the ribs to the sternum. The rib cage protects the heart, lungs and main blood vessels in the chest. The intercostal muscles located between the ribs, work together to allow the rib cage to expand and contract.
Lung Expansion
The lungs are situated within the rib cage, and the top of the lungs rest 1 to 2 inches beneath and above the collarbones. Resting below the lungs is the diaphragm, a large muscle that works with the lungs during the process of breathing. The diaphragm separates the chest cavity from the abdominal cavity. When contracted during inhalation, the diaphragm moves downward, allowing the lungs to fill with air. When relaxed during exhalation, it arches up, helping to expel air. The diaphragm and the intercostal muscles work together to allow the lungs to expand and relax as you breathe.
