E f f e c t s o f a g i n g a n d s m o k i n g o n t h e r e s p i r a t o r y s y s t e m
F ig u r e 1 3 . 1 0
Airways and respiratory
tissues become more rigid.
Ciliary action of the
epithelial linings of the
respiratory tracts decrease.
The chest wall becomes
less pliable.
Aging decreases alveolar
macrophage activities, which
increases susceptibility to
various diseases.
Age-related changes of the
respiratory tissues also
decrease the blood oxygen
levels.
The linings of the airways
are irritated, causing
inflammation and
obstructive pulmonary
diseases.
Substances in cigarette
smoke stimulate
uncontrolled cellular growth
in the lungs.
Smoking destroys the
alveoli.
The carbon monoxide in
cigarette smoke displaces
oxygen from hemoglobin
and reduces the amount of
oxygen that can be
transported to cells and
tissues.
Aging
Smoking
Lung capacity decreases as the
elasticity of chest and lung tissues
decreases.
Diffusion of 0 2|
>
Diffusion of C02i
- V
v
/ i
Pulmonary gas exchange is affected,
decreasing the level of O2 and increasing
the level of CO2 in the blood.
Results
Airway flow decreases.
Diseases and Behavioral Activities Can
Also Affect the Breathing Process
Exercise stimulates the respiratory system, but aging and
disease can compromise it. Airways and respiratory tissues
become more rigid and less elastic with age. The chest wall
also becomes less pliable. This loss of flexibility results in
decreased lung capacity (Figure 13.10); vital capacity can
decrease by as much as 35% by age 70. Aging also decreases
alveolar macrophage activities and ciliary action of the
epithelial linings of the respiratory tracts, which increases
susceptibility to various diseases. Age-related changes of the
respiratory tissues also decrease the blood oxygen levels.
Diseases such as bronchitis, pneumonia, and emphy-
sema reduce the flow of air through the airways
(obstructive
p u lm o n a ry diseases)
and decrease lung volumes and capaci-
ties
(restrictivep u lm o n a ry diseases),
as well as the diffusion of
gases between the alveoli and the pulmonary capillaries.
Pulmonary infections (such as pneumonia or tuberculosis)
can destroy the alveolar membranes and cause multiple
respiratory problems.
Infections (bacterial or viral) can also cause airway in-
flammation, mucus accumulation, and damage to alveoli.
Pulmonary edema, a buildup of fluid in the interstitial
spaces and alveoli, can occur as the pulmonary capillary
membrane breaks down from disease, infection, or con-
gestive heart failure. Such edema is generally caused by
increases in filtration (see Chapter 11). The fluid buildup
produces barriers to the diffusion of gases during external
respiration. This is primarily because of the solubility is-
sue discussed earlier. Oxygen must be forced to remain in
solution; with the extra fluid that must be traversed before
the oxygen arrives at the hemoglobin, much of the oxygen
goes back into the air before it can be trapped in the blood
supply. The excess fluid can also make the lung tissue less
flexible and decrease pulmonary ventilation.
Smoking Can Damage Lung Tissue
Smoking is a major contributing factor in the development
of pulmonary disease, as shown in Figure 13.10. Smoke
irritates the linings of the airways, causing inflamma-
tion and obstructive diseases such as chronic bronchitis.
Smoke contains chemicals that can paralyze the cilia of
the tracheal lining, allowing various contaminants (such
as bacteria, viruses, and toxic chemicals) to reach the al-
veoli. It also destroys the alveoli, which interferes with gas
exchange and makes the lung tissues less elastic, causing
emphysema. Cigarette smoke also contains carbon mon-
oxide, which displaces oxygen from hemoglobin and re-
duces the amount of oxygen that can be transported to
Good Respiratory Health is Essential 391
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