Gas Exchange

Question 1

Why is it not possible
to expel all air from
the lungs?

Answer 1

-thorax cannot be
completely flattened
-trachea/bronchi held
open by cartilage

Question 2

Why are specialised
exchange surfaces
are needed by some
organisms?

Answer 2

-they have a low SA:V
so exchange surfaces
increase that
-maximise efficiency
of diffusion
-ensure the demand
for oxygen and
glucose is met

Question 3

What are the 4
features of efficient
exchange surfaces?

Answer 3

-Increased
surface area
-Thin layers
-Good blood supply
-Ventilation to
maintain a diffusion
gradient

Question 4

Why does an
increased surface
area make an
exchange surface
efficient?

Answer 4

Provides the area
needed for exchange
overcomes limitations
of low SA:V ratio

Question 5

Why does a good
supply make an
exchange surface
efficient?

Answer 5

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

Question 6

Why does ventilation
make an exchange
surface efficient?

Answer 6

For gases ventilation
helps to maintain
concentration
gradients

Question 7

How is the nasal
cavity adapted for the
gas exchange
system?

Answer 7

-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

Question 8

How is the trachea
adapted for the gas
exchange system?

Answer 8

-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

Question 9

What is the function

of goblet cells?

Answer 9

Secrete mucus which
traps dust and
microogranisms

Question 10

What is the function
of ciliated epithelial
cells?

Answer 10

Cilia beat and move
mucus away from the
lungs, protecting
them

Question 11

How are the bronchi
adapted for the gas
exchange system?

Answer 11

-supported by small

rings of cartilage

Question 12

How are bronchioles
adapted for the gas
exchange system?

Answer 12

-contain no cartilage
-contain smooth
muscle
-smooth muscle
contracts when
bronchioles constrict
and relaxes when they
dilate

Question 13

How are the alveoli
adapted for the gas
exchange system?

Answer 13

-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

Question 14

What is breathing?

Answer 14

The movement of air

in and out of the lungs

Question 15

What is gas

exchange?

Answer 15

the delivery of oxygen
from the lungs to the
bloodstream and the
elimination of carbon
dioxide from the
blood stream

Question 16

Outline the steps in

inspiration

Answer 16

-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

Question 17

Outline the steps in

normal expiration

Answer 17

-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

Question 18

Outline the steps in

forced expiration

Answer 18

-abdominal muscles
contract, pushing
diaphragm upward
quickly making lung
pressure less negative
-internal intercostal
muscles contract
pulling ribs down hard
and fast

Question 19

What is inspiration?

Answer 19

movement of air into lungs

Question 20

what’s expiration?

Answer 20

movement of air out of lungs

Question 21

Does inspiration require energy?

Answer 21

yes

Question 22

Does expiration require energy?

Answer 22

no, passive process