Chronic Obstructive Lung Disease - Introduction

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Click the icon to see an image of emphysema.

Chronic Bronchitis

Chronic bronchitis is defined as coughing and excess mucus production that occurs for at least 3 months, during at least 2 consecutive years. In chronic bronchitis, the disease process generally has the following characteristics:

• Inflammation of the bronchial tubes (from smoking, air pollution, etc.) causes the production of mucus, which clogs the airways and makes breathing difficult.
• The mucus is cleared through coughing. Both constant coughing and inflammation can damage the bronchial tubes. The tubes swell and thicken, leaving less room for air flow.

Click the icon to see an image of bronchitis.

The Lungs

The lungs are two spongy organs surrounded by a thin, moist membrane called the pleura. Each lung is made up of smooth, shiny lobes. The right lung has three lobes, and the left has two. About 90% of the lung is filled with air; only 10% is solid tissue.

When a person inhales, air travels through the following pathways into the lungs:

• Air is carried from the windpipe (trachea) into the lung through flexible airways called bronchi.
• Like the branches of a tree, bronchi divide into more than a million smaller airways called bronchioles.
• The bronchioles lead to grape-like clusters of microscopic sacs called alveoli.
• In each adult lung there are millions of these tiny alveoli. The thin membrane of the alveoli allows oxygen and carbon dioxide to pass to and from capillaries.
• When the person breathes in deeply, the elastic alveoli unfold and unwind to allow this exchange of gases to occur.

Capillaries, the smallest of the blood vessels, carry blood throughout the body. Red blood cells carry oxygen throughout the body, and return carbon dioxide to the lungs. White blood cells are the critical infection fighters in the body.

Click the icon to see an image of normal lungs.

Review Date: 04/10/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).