Download Topic 6.4

Topic 6.4
Gas Exchange
Why do we need Oxygen???
• Aerobic cellular respiration
– Biochemical pathway
– Chemical bonds within a glucose molecule
are broken..releasing Energy
– This E is stored as ATP
– Requires O2 and gives off CO2
– Each of the 6 C in glucose are given off as
CO2
6.4.1 Distinguish between
ventilation, gas exchange and
cellular respiration
• Ventilation = breathing (filling lungs with
air and exhaling)
• Gas exchange = the movement of gases
– O2 in the lung tissues diffuses into the
bloodstream
– CO2 from blood diffuses into lung tissues
– Occurs in two locations:
• In the lungs
• In capillary beds where CO2 diffuses into blood
and O2 diffuses into body cells
Relationship between ventilation, gas
exchange and cell respiration
Lung
air
air
ventilation
CO2 diffuses out of alveolus
O2 diffuses into alveolus
CapillaryCo2 diffuses out of
lung capillaries
gas exchange
Co2 diffuses into
body capillaries
Body Cell
O2 diffuses into
lung capillaries
O2 diffuses out of
body capillaries
cell respiration
O2 is a reactant for aerobic cellular respiration
CO2 is a product of aerobic cellular respiration
6.4.2 Explain the need for a
ventilation system
• Amoeba has no ventilation system????
• They need gas exchange????
• Our bodies are so thick-only our outside
cells are exposed to air
– All our cells need O2 and are too far away to
make use of diffusion of O2 and CO2
• Maintain [ ] levels of gases within the
lungs
Anatomy of the Ventilation System
Pathway of the Ventilation System
•
•
•
•
•
Air enters your trachea
Passes into your right and left 1◦ bronchi
Branches smaller and smaller
Smallest branches = bronchioles
Finally, air enters the small air sacs called
alveoli
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–
–
–
Clustered at the ends of the smallest bronchioles
Appearance similar to “bunch of grapes”
Approx. 300 million in lungs
Surrounded by capillary bed
6.4.3
Features of Alveoli that adapt them to gas exchange
Adaptation
Advantage
spherical shape
provides a large surface area for
respiratory gases to diffuse
through
flattened, single cell prevents respiratory gases from
thickness
having to diffuse through more
cell layers
moist inner lining
allows for efficient diffusion
associated capillary respiratory gases do not have to
bed nearby
diffuse far to reach single cell
thick capillaries
6.4.5 Mechanisms of Ventilation
• Tissues that make up our lungs are passive…not
muscular
• Muscles surround the lungs
– Diaphragm
– Abdominal muscles
– Intercostal (rib) muscles
• Breathing is based on the inverse relationship
between pressure and volume
– in volume leads to a in pressure
– Lungs are in thoracic cavity (thorax) which is a closed
environment
– Lungs have opening through the trachea (via nose and
mouth)
– These 2 environments (lungs and thorax) affect each other
6.4.5 Mechanisms of Ventilation (cont.)
•
Mechanisms of Inspiration: (steps reversed for
expiration)
1. Diaphragm contracts while abdominal and
intercostal muscles raise the rib cage…this the
volume of thoracic cavity
2. Since volume in thoracic cavity, the pressure
which leads to less pressure pushing on the
passive lung tissue
3. Lung tissue in volume since there is less
pressure
4. in pressure inside lungs is known as partial
vacuum
5. Air comes in through mouth and nose to counter
the partial vacuum (fills alveoli with air)
2 Questions
1. Create a list of steps which represent what
your body would do to accomplish a single
expiration (breathing out).
2. Pneumonia (excess mucus) and smoking
(tar) create an extra lining inside of each
of the alveoli. Describe how and why this
could become life threatening.