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The Respiratory System
Why do we breathe?
Just Breathe!
• We’re warm-blooded creatures
who require OXYGEN to survive!
• Function of the Respiratory System:
provides oxygen FOR the body and
allows carbon dioxide to leave the body
• Works closely with the circulatory system
to accomplish this gas exchange
“When you can’t breathe, nothing else matters.”
Canadian Lung Association
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The Respiratory System:
• Respiration:
Why do we need to breath oxygen?
– all processes involved in the exchange of
oxygen and carbon dioxide between cells &
the environment
O2
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CO2
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The Respiratory System:
Types of Respiration:
• PRIMARY function:
BREATHING (for gas exchange) – oxygen and
carbon dioxide
1.) To get oxygen (O2) to its cells
2.) To get rid of excess carbon dioxide (CO2)
O2
• Also used to produce SOUND
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External Respiration
• gas exchange with the surrounding air
• (O2 and CO2 )
CO2
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Types of Respiration:
HUMAN ADAPTATIONS
• For efficient gas exchange to occur:
Internal Respiration
• gas exchange at the cellular level
• (cellular respiration)
1. Water must be present at the respiratory
surface.
• glucose + oxygen → carbon dioxide + water + energy
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Adaptation:
Human lung located within the body cavity
which contains a lot of water and air is
moistened when it enters lungs.
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HUMAN ADAPTATIONS
The Human Respiratory System
2. The respiratory surface must be large
Adaptation: Massive surface area
Larynx
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Nasal Cavity
Path taken by air
Upper
Path taken by food Respiratory
Pharynx
Tract
Epiglottis
Esophagus
Trachea
Bronchi
Bronchioles
Lower
Respiratory
Alveoli
Tract
Diaphragm
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External Respiration:
Mechanics of Breathing
2 Phases:
• Inspiration
https://medlineplus.gov/ency/anatomyvideos/000018.htm
– diaphragm contracts, volume increases,
creating low pressure and drawing air in
• Expiration
– diaphragm relaxes, volume decreases,
creating high pressure, forcing air out
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Mechanics of Breathing
Breathing Movements
• The body uses muscles to change the
VOLUME of the thoracic cavity.
• This alters the PRESSURE inside the
lungs
• An increase in volume = decrease in
pressure (and vice versa)
• Gas moves from an area of high pressure
to an area of low pressure
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Respiratory Muscles
• Diaphragm: dome shaped
sheet of muscle separating
thoracic and abdominal
cavities.
• Intercostal muscles:
muscles of the ribcage
– External intercostals:
outer surface, pull ribs
up
– Internal intercostals:
inner surface, pull ribs
down
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Breathing
Mechanics of INSPIRATION
• Diaphragm CONTRACTS and FLATTENS (moves
downwards)
• Intercostals CONTRACT and move ribcage UPWARDS
• Pleural membrane pulls on lungs
• Result:
– Lung volume:
INCREASED
– Pressure inside the lungs:
DECREASED
– AIR MOVES IN
• Inspiration: the act of taking air INTO the
lungs, occurs when pressure inside the
lungs is LOWER than pressure outside the
lungs (i.e. atmospheric pressure)
• Expiration: the act of breathing OUT,
occurs when pressure inside the lungs is
GREATER than pressure outside the
lungs (atmospheric)
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Mechanics of EXPIRATION
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Diaphragm RELAXES and RETURNS to DOME shape
Intercostals RELAX and move ribcage DOWNWARDS
Pleural Membrane no longer pulling on lungs
Result:
– Lung volume:
DECREASED
– Pressure inside the lungs:
INCREASES
– AIR MOVES OUT
• *Internal intercostals can pull
ribs in further to force exhalation
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Respiration and Gas Exchange
• Once inside the lungs, air is exchanged with the
gases in the bloodstream.
• External Respiration: The exchange of O2 and
CO2 between air and blood (occurs in the lungs).
• The alveoli are surrounded by tiny blood vessels
(capillaries); both have walls that are only a
single cell layer thick to allow for diffusion of
gases.
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Respiration and Gas Exchange
Respiration and Gas Exchange
• Once in the bloodstream, oxygen travels
throughout the body.
• the gases are exchanged due to differences in
CONCENTRATION.
– O2 in inhaled air > O2 in blood of capillaries in lungs.
– CO2 in inhaled air < CO2 in blood of capillaries in lungs.
• Internal Respiration: The exchange of O2 and
CO2 between blood and the cells of the
surrounding tissue (occurs in the body tissues).
• So in external respiration,
– O2 diffuses from the alveoli to the capillaries and
– CO2 diffuses from the capillaries to the alveoli.
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• As blood passes body cells O2 diffuses from the
capillaries to the tissue and CO2 diffuses from
the tissue to the capillaries.
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Lung Capacities
Lung Capacities
• The full capacity of your lungs is not used up under
normal conditions - consider yawning, or blowing
out a candle, or exercising.
• A spirometer is used to measure lung capacities
and produces a spirograph
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• Tidal Volume: volume of air inhaled and
exhaled in a normal breathing movement
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Lung Capacities
Lung Capacities
• Expiratory Reserve Volume: the
additional volume that can be forced out of
lungs
• Vital Capacity: the total volume of gas
that can be moved in or out of the lungs
• Inspiratory Reserve Volume: the additional
volume of air that can be taken in, beyond a
regular or tidal inhalation.
• Inspiratory Capacity: total volume of air that
can be taken in
=(TV + IRV)
TV + IRV + ERV = VC
IRV
IRV
ERV
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Lung Capacities
• Residual Volume: the amount of gas that
remains in the lungs and passageways of
the respiratory system even after full
exhalation (prevents collapse, no value for
gas exchange)
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