Transcript Pulmonary Volumes and Capacities

BY Dr : FARIHA RIZWAN
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TIDAL VOLUME
volume of air inspired or expired with each
normal breath; it amounts to about 500
milliliters
INSPIRATION RESERVE VOLUME
the extra volume of air that can be inspired
over and above the normal tidal volume when
the person inspires with full force; it is usually
equal to about 3000 milliliters.
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EXPIRATORY RESERVE VOLUME
the maximum extra volume of air that can be expired
by forceful expiration after the end of a normal tidal
expiration; this normally amounts to about 1100
milliliters.
RESIDUAL VOLUME
the volume of air remaining in the lungs after the
most forceful expiration; this volume averages about
1200 milliliters.
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INSPIRATORY CAPACITY
tidal volume + the inspiratory reserve volume.
about 3500 milliliters
IC = Vt + IRV
FUNCTIONAL RESIDUAL CAPACITY
expiratory reserve volume + the residual volume.
This is the amount of air that remains in the
lungs at the end of normal expiration (about
2300 milliliters).
FRC =ERV +RV
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VITAL CAPACITY
inspiratory reserve volume + tidal volume + expiratory
reserve volume
VC = IRV + Vt +ERV
maximum amount of air a person can expel from the
lungs after first filling the lungs to their maximum
(about 4600 milliliters)
TOTAL LUNG CAPACITY
is the maximum volume to which the lungs can be
expanded with the greatest possible effort (about
5800 milliliters); it is equal to the vital capacity plus
the residual volume
TLC= VC + RV
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VC = IRV + VT + ERV
VC = IC + ERV
TLC = VC + RV
TLC = IC + FRC
FRC = ERV + RV
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MINUTE RESPIRATORY VOLUME:
is the total amount of new air moved into the
respiratory passages each minute
equal to the tidal volume * respiratory rate per minute
The normal tidal volume is about 500 milliliters, and
the normal respiratory rate is about 12 breaths per
minute.
Therefore, the minute respiratory volume averages about
6 L/min. A person can live for a short period with a
minute respiratory volume as low as 1.5 L/min and a
respiratory rate of only 2 to 4 breaths per minute
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Respiratory Unit. A respiratory unit (also called "respiratory
lobule“) is composed of a respiratory bronchiole, alveolar
ducts and alveoli.
There are about 300 million alveoli in the two lungs, and
each alveolus has an average diameter of about 0.2
millimeter.
The alveolar walls are extremely thin, and between the
alveoli is an almost solid network of interconnecting
capillaries.
because of the extensiveness of the capillary plexus, the
flow of blood in the alveolar wall has been described as a
"sheet" of flowing blood.
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Thus, it is obvious that the alveolar gases are in
very close proximity to the blood of the
pulmonary capillaries.
Further, gas exchange between the alveolar air
and the pulmonary blood occurs through the
membranes of all the terminal portions of the
lungs, not merely in the alveoli themselves.
All these membranes are collectively known as
the respiratory membrane, also called the pulmonary
membrane.
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1- The thickness of the respiratory membrane: The
rate of diffusion through the membrane is inversely
proportional to the thickness of the membrane.
2- The surface area of the respiratory membrane :
The rate of diffusion through the membrane is directly
proportional to the surface area of the lungs
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3- The diffusion coefficient for transfer of each
gas through the respiratory membrane
depends on the gas's solubility in the
membrane.
The rate of diffusion in the respiratory
membrane is almost exactly the same as that in
water
The difference between these two pressures is a
measure of the net tendency for the gas molecules to
move through the membrane.
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When the partial pressure of a gas in the alveoli is
greater than the pressure of the gas in the blood, as is
true for oxygen, net diffusion from the alveoli into the
blood occurs.
When the pressure of the gas in the blood is greater
than the partial pressure in the alveoli, as is true for
carbon dioxide, net diffusion from the blood into the
alveoli occurs.
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Gas exchange between blood in systemic
capillaries and working tissue
O2 is high in the blood and low in the tissue so
O2 diffuses from blood into tissue
CO2 is low in the blood and high in the tissue
so CO2 diffuses from tissue to blood
Breathing air in and out of the lungs
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As the ribs rise and fall and the diaphragm
domes and flattens, the volume and
pressure in the lungs changes
The changes in pressure that cause air to
enter and leave the lungs
Inspiration/Expiration: air in/air out
 Cycle:
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Relaxed state: diaphragm and intercostal muscles
relaxed
Inspiration: diaphragm contracts, pulling muscle
down, intercostal muscles contract elevating chest
wall and expanding volume of chest, lowering
pressure in lungs, pulling in air
Expiration: muscles relax, diaphragm resumes
dome shape, intercostal muscles allow chest to
lower resulting in increase of pressure in chest
and expulsion of air
As we exercise, the body needs to obtain
more oxygen and remove more carbon
dioxide (CO2)
This is done by increasing the rate
and depth of breathing
An increase in carbon dioxide in the blood is
the main trigger that increases the rate and
depth of breathing
Chemoreceptors in the respiratory centre in
the brain stem’s medulla detect an increase
in blood CO2 levels
The intercostal and phrenic nerves
increase the rate and depth of breathing
Additional chemoreceptors on arteries
near the heart monitor oxygen and blood
acidity
Control of Respiration
chemoreceptors
on aorta and carotid
artery
brain
heart
intercostal
nerve to
external
intercostal
muscles
Phrenic
nerve to
diaphragm
ribs
diaphragm
THAT’S ALL FOR TODAY