Ventilation and Gas Exchange
This photo (courtesy of the Anatomical Institute, Bern) shows a rubber cast of human lungs
The
Human
Respirator
y System
Assignment
1. Draw, label and annotate a diagram of
the human ventilation system. Include a
pull-out of the alveoli.
What is cellular respiration?
When an organism takes in organic nutrients
and converts them to a usable for of energy,
namely ATP.
*****See your notes from last year to review
this. Anything about cellular respiration is
fair game for this exam.*****
What is gas exchange?
1. Exchanging of oxygen and carbon
dioxide in the capillaries of the alveoli
2. Based on concentration gradients
3. Does not require energy (because it uses
diffusion)
Bronchiole and Alveolar
Structures
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Adaptations of the Alveoli
1. Large surface area = increases amount of diffusion that
can occur
2. Thin epithelial layer = short diffusion distance for gases
3. Moist = prevents alveoli from sticking to each other
4. Surrounded by capillaries = large blood supply
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What is ventilation?
1. The mechanical action of the muscles
surrounding the lungs moving air in and
out (Air is refreshed with every
ventilation)
2. Based on volume and pressure changes
3. Requires energy (muscle use)
How does ventilation occur?
Involves inspiration (inhaling) and expiration (exhaling)
1.Inspiration
a. External intercostal muscles contract
b. Pull ribs out and up
c. Diaphragm contracts and flattens (or lowers)
d. This allows a decrease in pressure and an
increase in volume
e. Air flows into the lungs
How does ventilation occur? (cont.)
Involves inspiration (inhaling) and expiration (exhaling)
2. Expiration
a. Internal intercostal muscles contract
b. Pull rib cage in and down
c. Diaphragm relaxes and moves upward
d. Creates and increase in pressure and a
decrease in volume
e. Air is forced out of the lungs
Internal
intercostals
External
intercostals
Variations in lung volume
Why do we need a ventilation
system?
1. Related to the surface are to volume ratio
2. As organisms get larger the ratio decreases
3. We don’t have enough surface area for
efficient gas exchange.
4. It would take too long for the gases to reach
our organs through diffusion alone because
our volume is too large.
5. Instead of diffusion from the body’s surface,
the alveoli’s increased surface area and
capillaries allow enough gas exchange to
support the entire body
6. We need a constant supply of oxygen to all
organs to support cellular respiration
Examples of other ventilation
systems
1. Insects have tracheal tubes running through
out their bodies
a. This allows diffusion of gas throughout
b. Air enters or exits through the insects
exoskeleton
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Examples of other ventilation
systems
1. Larval amphibians
have external gills
a. Have large surface
are to aid gas
exchange
b. Work similar to
lungs and alveoli to
exchange gases
c. Easily damaged
because of location
d. Example:
salamander
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Examples of other ventilation
systems
1. Fish have internal gills
a. These are the same as
external gills but are
protected
b. As the fish opens or
moves its mouth water
flows in
c. As the fish closes its
mouth or continues
movement water is forced
through the gills and gill
slits
d. The gills provide a surface
Examples of respiration without a
ventilation system or circulation
1.
2.
3.
4.
5.
6.
Bacteria
Fungi
Flatworms
Sponges
Jellyfish
Plants
Assignment
1. Explain how ventilation, gas exchange
and cellular respiration are
interdependent.
Asthma