Tobacco

Tobacco products are legal for people age 18 and older. Nicotine is the major drug found in tobacco, shown in Figure 49-17. Nicotine is a highly addictive stimulant. When a person chews tobacco or inhales its smoke, nicotine is absorbed into the bloodstream through the mouth and lungs. It is then quickly transported throughout the body and, in pregnant women, to the fetus.

Nicotine mimics the action of a neurotransmitter called acetylcholine (AS-i-TlL-KOH-leen). Acetylcholine plays a role in many of the body's everyday activities. Nicotine increases blood pressure and heart rate. Nicotine decreases the oxygen supply to body tissues and the blood supply to the hands and feet. Nicotine is also a poi-son—60 mg of nicotine is a lethal dose for an adult.

Nicotine is not the only harmful substance found in tobacco. Burning tobacco produces tars, complex mixtures of chemicals and smoke particles. Tars coat and paralyze the cilia that line air passages and normally sweep particles and debris from those passageways. Tars irritate the nose, throat, trachea, and bronchial tubes, causing sore throat and coughing. Tars disrupt lung cells, reducing breathing capacity and increasing the risk of respiratory infections.

The long-term use of tobacco products has several effects. In the United States, smoking-related illnesses cause more than 400,000 deaths each year. About 25 percent of all heart attacks are associated with the use of tobacco. Smoking causes lung cancer, one of the most common forms of cancer. Many smokers contract chronic bronchitis (brahn-KIET-is), an inflammation of the bronchi and bronchioles, or emphysema (EM-fuh-SEE-muh), a degenerative lung disease in which alveoli lose their elasticity and eventually rupture.

People who chew tobacco and use snuff have higher rates of lip, gum, and mouth cancer than people who don't use smokeless tobacco. Pregnant women who smoke are twice as likely as nonsmoking mothers to suffer miscarriages. Their babies tend to have lower birth weights than babies of nonsmokers and are twice as likely to die in the first few months of life.

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Quit Smoking Today

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