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The lungs are a pair of organs in the chest that are primarily responsible for the exchange of oxygen and carbon dioxide between the air we breathe and the blood. The lung is composed of clusters of small air sacs (alveoli) divided by thin, elastic walls or membranes. Capillaries, the tiniest of blood vessels, run within these walls between the alveoli and allow blood and air to come near each other. The distance between the air in the lungs and the blood in the capillaries is very small, and allows molecules of oxygen and carbon dioxide to transfer across the membranes. Air reaches the alveoli via the bronchial tree. The trachea splits into the right and left mainstem bronchi, which branch further into bronchioles and finally ends in the alveolar air sacs. When we breathe in, air enters the lung and the alveoli expand. Oxygen is transferred onto hemoglobin molecules in the red blood cells to be transported to the rest of the body for use. As oxygen attaches to the red blood cell, carbon dioxide, the waste product of metabolism, detaches and crosses into the alveoli to be exhaled. When we breathe out, the alveoli get squeezed by the elasticity in their walls and air is pushed out of the lungs.
Emphysema, also called pulmonary emphysema, is an abnormal distention of the lungs with air; in patients with emphysema, the air ducts and the air sacs, or alveoli, are distended, and there is destruction of the partitions between alveoli and loss of alveoli. Emphysema is one of several diseases usually labeled collectively as chronic obstructive pulmonary disease (COPD). It's the most common cause of death from respiratory disease in the United States; approximately 2 million Americans are afflicted with the disease. Emphysema (COPD) appears to be more prevalent in men than women. Postmortem findings reveal few adult lungs without some degree of emphysema.
The main cause of emphysema is smoking, which activates inflammatory cells in the lung. This...