767
CHAPTER NINETEEN
Respiratory System
HCO
3
Red blood cell
HCO
3
Cl
Cl
Cl
HCO
3
Plasma
Capillary wall
FIGURE 19.42
As bicarbonate ions (HCO
3
) dif
use out oF the red
blood cell, chloride ions (Cl
) From the plasma dif
use into the cell,
maintaining the electrical balance between ions. This exchange oF ions
is called the chloride shiFt.
Long-term exposure to particulates in the workplace can also
raise the risk of developing these conditions. Still, many age-
associated changes in the respiratory system are unavoidable.
With age, protection of the lungs and airways falters,
as ciliated epithelial cells become fewer, and their cilia
less active or gone. At the same time, mucus thickens; the
swallowing, gagging, and coughing refl
exes slow; and mac-
rophages lose their efficiency in phagocytizing bacteria.
These changes combine to slow the clearance of pathogens
alveolar air.
Figure 19.43
summarizes this process, and
table
19.7
summarizes the transport of blood gases.
PRACTICE
42
Describe three ways carbon dioxide can be transported From cells
to the lungs.
43
How can hemoglobin carry oxygen and carbon dioxide at the
same time?
44
How do bicarbonate ions help buf
er the blood (maintain its pH)?
45
What is the chloride shiFt?
46
How is carbon dioxide released From the blood into the lungs?
19.8
LIFE-SPAN CHANGES
Changes in the respiratory system over a lifetime reflect
both the accumulation of environmental infl uences and the
effects of aging in other organ systems. The lungs and respi-
ratory passageways of a person who has breathed only clean
air are pinker and can exchange gases much more efF ciently
as the years pass than can the respiratory system of a person
who has breathed polluted air and smoked for many years.
Those who have been exposed to foul air are more likely to
develop chronic bronchitis, emphysema, and/or lung cancer.
TABLE
19.7
|
Gases Transported in Blood
Gas
Reaction
Substance Transported
Oxygen
Combines with iron atoms oF hemoglobin molecules
Oxyhemoglobin
Carbon dioxide
About 7% dissolves in plasma
Carbon dioxide
About 23% combines with the amino groups oF hemoglobin molecules
Carbaminohemoglobin
About 70% reacts with water to Form carbonic acid; the carbonic acid then dissociates to release hydrogen
ions and bicarbonate ions
Bicarbonate ions
CO
2
CO
2
CO
2
Alveolus
Alveolar wall
P
CO
2
= 40 mm Hg
Capillary wall
CO
2
H
2
O
H
2
CO
3
+
HCO
3
HCO
3
H
+
H
+
released
from hemoglobin
+
Carbaminohemoglobin
CO
2
hemoglobin
+
Blood
flow to
pulmonary
venule
CO
2
dissolved
in plasma
Blood flow
from pulmonary
arteriole
Plasma
Red blood cell
P
CO
2
= 40 mm Hg
P
CO
2
= 45 mm Hg
FIGURE 19.43
In the lungs, carbon dioxide dif
uses From the blood into the alveoli.
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