RESPIRATORY DISTRESS SYNDROME
RESPIRATION
R
The function of respiration is to
provide the energy needed by body
cells. Cells obtain this energy mainly
by metabolizing glucose with oxygen,
and so they require a constant supply
of oxygen. In addition, the waste
products of the metabolic process
(mainly carbon dioxide) must be
carried away from the cells.
Respiration includes the breathing
of air into the lungs, the transfer of
oxygen from the air to the blood, the
transport of oxygen in the blood to the
body cells, the metabolism of glucose
with oxygen in the cells, and the
transport of carbon dioxide to the
lungs to be breathed out.
During exercise, respiration
increases to compensate for higher
energy demands by muscle cells.
Artery
Alveolus
Carbon dioxide (CO2)
Lung -
Alveoli
Pulmonary vein -
Bronchiole
Network o f capillaries
I
Air, containing oxygen, is
breathed into the lungs and
enters the alveoli (tiny air sacs).
Oxygen diffuses from the air into
the blood vessels surrounding
the alveoli.
2
The oxygen-
saturated
blood passes
from the lungs via
the pulmonary
veins to the left
side of the heart.
Aorta
Bronchus
Pulmonary
artery
Leftside
of heart
Right side
of heart
6
Carbon dioxide
is carried back
in the blood to the
heart, then to the
lungs, where it
diffuses into the
alveoli and is
breathed out of
the body.
5
Within body cells, glucose
and oxygen take part in a
complex series of reactions
that provide energy to power
the cells. During this cellular
respiration (left), glucose is
converted to carbon dioxide
and water, which, as waste
products, are picked up by
the blood.
BREATHING VOLUMES
One way the body copes with
varied demands for oxygen is
through changes in breathing
volume. The tidal volume - the
amount breathed into and out
of the lungs at each breath - may
vary from 0.5 litre at rest, up to 4.5
litres (near the maximum or vital
capacity) during heavy exercise.
4
As the blood
passes through
tissue capillaries, it
gives up oxygen (and
nutrients such as
glucose) to the body
tissues and cells.
Vein
658
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