188 ChapteR 10respiratory system Disorders: tobacco, irritants,
and apnea
A variety of infections and other disorders can prevent
the respiratory system from functioning properly. Some
of these problems develop when we inadvertantly inhale
pathogens or noxious substances, while others we bring
on ourselves.tobacco is an avoidable threat
People who start smoking tobacco begin wreaking havoc
on their lungs. Smoke from a single cigarette can prevent
cilia in bronchioles from beating for hours. Toxic particles
smoke contains can stimulate mucus secretion and kill
the infection-fighting phagocytes that normally patrol the
respiratory epithelium.
Today we know that cigarette smoke, including
secondhand smoke inhaled by a nonsmoker, causes lung can-
cer (see more in Section 10.8) and contributes to heart disease
and other ills. Figure 10.18 summarizes the known health
risks associated with tobacco smoking,
as well as the benefits of quitting.
In recent years so-called electronic
cigarettes (right) have become a popular
substitute for the “real thing.” E-cigarette
users inhale flavored water vapor. Many
of the devices can contain liquid nico-
tine in the brew. Proponents say that
e-cigarettes are a safe alternative to smok-
ing tobacco because users aren’t exposed10.7
F i g u r e 10.18 From the american Cancer Society, a list of the risks incurred by smoking and the benefits of quitting.Effects of Smoking Benefits of Quitting
Shortened life expectancy Nonsmokers live about 8.3 years longer Cumulative risk reduction; after 10–15 years, the life
than those who smoke two packs a day from their mid-twenties on. expectancy of ex-smokers approaches that of nonsmokers.
Chronic bronchitis, emphysema Smokers have 4–25 times higher Greater chance of improving lung function and slowing
risk of dying from these diseases than do nonsmokers. down rate of deterioration.
Cancer of lungs Cigarette smoking is the major cause. After 10–15 years, risk approaches that of nonsmokers.
Cancer of mouth 3–10 times greater risk among smokers. After 10–15 years, risk is reduced to that of nonsmokers.
Cancer of larynx 2.9–17.7 times more frequent among smokers. After 10 years, risk is reduced to that of nonsmokers.
Cancer of esophagus 2–9 times greater risk of dying from this. Risk proportional to amount smoked; quitting should reduce it.
Cancer of pancreas 2–5 times greater risk of dying from this. Risk proportional to amount smoked; quitting should reduce it.
Cancer of bladder 7–10 times greater risk for smokers. Risk decreases gradually over 7 years to that of nonsmokers.
Cardiovascular disease Cigarette smoking is a major contributing Risk for heart attack declines rapidly, for stroke declines more
factor in heart attacks, strokes, and atherosclerosis. gradually, and for atherosclerosis it levels off.
Impact on offspring Women who smoke during pregnancy have When smoking stops before fourth month of pregnancy,
more stillbirths, and the weight of liveborns is lower than the average risk of stillbirth and lower birth weight eliminated.
(which makes babies more vulnerable to disease and death).
Impaired immunity More allergic responses, destruction of white Avoidable by not smoking.
blood cells (macrophages) in respiratory tract.
Slow bone healing Surgically cut or broken bones may take Avoidable by not smoking.
30 percent longer to heal in smokers, perhaps because smoking
depletes the body of vitamin C and reduces the amount of oxygen
delivered to tissues. Reduced vitamin C and reduced oxygen interfere
with formation of collagen fibers in bone (and many other tissues).to tars or other toxic substances in tobacco smoke. Critics,
including experts at the Centers for Disease Control and
Prevention, point out that nicotine is more addictive than
heroin. They are concerned that “smoking” nicotine-laced
vapor flavored like “chocolate chip cookie” or “raspberry”
may lure consumers, especially young ones, to try the old-
fashioned, health-destroying variety. According to a 2013
report of the CDC’s Office on Smoking and Health, some 75
percent of middle-school and high-school students who use
e-cigarettes also smoke regular cigarettes.irritants cause other disorders
In cities, in certain occupations, and anywhere near a
smoker, airborne particles and irritating gases put extra
workloads on the lungs.
Bronchitis can be brought on when air pollution
increases mucus secretions and interferes with ciliary
action in the lungs. Ciliated epithelium
in the bronchioles is especially sensi-
tive to cigarette smoke. Mucus and the
particles it traps—including bacteria—
accumulate in airways, coughing
starts, and the bronchial walls become
inflamed. Bacteria or chemical agents
start destroying the wall tissue. Cilia
in the lining die, and mucus-secreting
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