Gas Exchange Flashcards
Why is it not possible
to expel all air from
the lungs?
-thorax cannot be
completely flattened
-trachea/bronchi held
open by cartilage
Why are specialised
exchange surfaces
are needed by some
organisms?
-they have a low SA:V so exchange surfaces increase that -maximise efficiency of diffusion -ensure the demand for oxygen and glucose is met
What are the 4
features of efficient
exchange surfaces?
-Increased surface area -Thin layers -Good blood supply -Ventilation to maintain a diffusion gradient
Why does an increased surface area make an exchange surface efficient?
Provides the area
needed for exchange
overcomes limitations
of low SA:V ratio
Why does a good
supply make an
exchange surface
efficient?
the greater the difference in concentration the greater the rate of diffusion. A good supply means substances are constantly being delivered and removed, maintaining the steep concentration gradient
Why does ventilation
make an exchange
surface efficient?
For gases ventilation
helps to maintain
concentration
gradients
How is the nasal
cavity adapted for the
gas exchange
system?
-good blood supply warms air to body temperature -cells secrete muscus to trap dust and bacteria to protect lung tissue -moist surfaces reduce evaporation from the exchange surfaces which increase humidity
How is the trachea
adapted for the gas
exchange system?
-supported by incomplete rings of strong, flexible cartilage to allow for movement and prevent the trachea from collapsing -lined with ciliated epithelium and goblet cells
What is the function
of goblet cells?
Secrete mucus which
traps dust and
microogranisms
What is the function
of ciliated epithelial
cells?
Cilia beat and move
mucus away from the
lungs, protecting
them
How are the bronchi
adapted for the gas
exchange system?
-supported by small
rings of cartilage
How are bronchioles
adapted for the gas
exchange system?
-contain no cartilage
-contain smooth
muscle
-smooth muscle
contracts when
bronchioles constrict
and relaxes when they
dilate
How are the alveoli
adapted for the gas
exchange system?
-very thin walls
-contain elastic fibres
which allow alveoli to
stretch as air is drawn
n and when they
return to size help
squeeze air out
-good capillary
blood supply
-coated in surfactant
What is breathing?
The movement of air
in and out of the lungs
What is gas
exchange?
the delivery of oxygen from the lungs to the bloodstream and the elimination of carbon dioxide from the blood stream
Outline the steps in
inspiration
-diaphragm flattens and contracts -external intercostal muscles contract making the ribs move up and out -this increases the volume of the thorax so reduces pressure -pressure is more negative than the atmosphere air -air is drawn into the lungs to equalise the pressures inside and outside the chest
Outline the steps in
normal expiration
-diaphragm relaxes and curves upwards -external intercostal muscles relax so ribs move in -decreases volume of the thorax -pressure in the lungs is less negative than atmospheric air -air moves out of the lungs until pressure inside and out is equal
Outline the steps in
forced expiration
-abdominal muscles contract, pushing diaphragm upward quickly making lung pressure less negative -internal intercostal muscles contract pulling ribs down hard and fast
What is inspiration?
movement of air into lungs
what’s expiration?
movement of air out of lungs
Does inspiration require energy?
yes
Does expiration require energy?
no, passive process
