24.
External respiration is the exchange of gases between the air and the
.
It takes place in the
i, which are small, spherical
s. Adjacent to the walls
of the alveoli are numerous blood
s. The wall of the alveolus contains a special
chemical known as
t. To make the transfer of gases possible, the inner
surface of the alveoli must be kept
t.
25.
The pleural cavities help to provide
n for the expansion and contraction
of the
s.
26.
Respiratory reflexes are controlled by the
y center in the medullary
portion of the h
m. One of the major influences upon this center is the
level of c
d
in the circulating blood.
27.
Providing nourishment and oxygen to the tissues of the lung is the _______
blood. Actually involved in the exchange of gases is the
blood.
28.
Functional blood is brought to and from the lungs by the
y cycle of the
cardiovascular system. This cycle includes the right
, the
arch,
the right and left
arteries, the
s in the vicinity of the alveoli,
the pulmonary
s system, and the (left) (right) atrium.
29.
Gases are transported between the alveoli and the individual cells by the
system. Some of the gases are dissolved directly in the
of
the blood. However, in humans, the greater percentage of the gases is carried within
the substance of the
s. Within these cells, there is a substance which readily
accepts and gives up oxygen; this substance is called
.
30.
In "mouth-to-mouth" resuscitation, the initial air forced into the patient is the
"
air," which still has its full amount of
.
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