Gaseous Exchange

Question 1

Give examples of materials that need to be interchanged between an organism and its environment.

Answer 1

• Respiratory gases (oxygen and carbon dioxide)
• Heat
• Nutrients
• Excretory products

Question 2

where does the exchange take place in an organism?

Answer 2

Exchanges takes place at the surface of an organism, and the materials absorbed are used by the cell. The cell or cells of the organism make up its
volume.

Question 3

Explain why small organisms have a high metabolic rate

Answer 3

Small organisms have a high metabolic rate as
they have a large surface area to volume ratio
and lose heat faster than larger organisms. They
have a high rate of respiration to maintain their
core body temperature.

Question 4

What makes a good exchange surface?

Answer 4

Large surface area
• Large concentration gradients – associated with an efficient transport
system
• Thin exchange surface – so short diffusion pathway
• Permeable
• Moist – gases diffuse more rapidly in solution

Question 5

What makes an efficient gas exchange surface in humans

Answer 5

In humans, the lungs are our respiratory interface with the environment.
In order to be an efficient gas exchange surface the lungs have a very small
diffusion distance and large surface area and as a result are delicate.
Therefore, the lungs would be easily damaged if the rib cage was not there to
protect them.

Question 6

1. What is the trachea?

Answer 6

Trachea (Wind pipe)
The trachea is a tube like structure that
carries air from the mouth to the lungs.

Question 7

2. What is the bronchi?

Answer 7

Bronchi
The trachea splits into two bronchi as it
enters the lungs, which allows air to travel
to the left and right lung (singular:
Bronchus)

Question 8

3. What is the bronchioles?

Answer 8

Bronchioles
The Bronchi further divide into smaller branches called bronchioles. These then
supply the alveoli with air.

Question 9

4. Describe the alveoli

Answer 9

The alveoli are small sacks at the end of the
bronchioles, that act as the interface
between the air in the lungs and the
blood. There are many alveoli and
their walls are folded to provide a
large surface area. In fact, the total
alveolar surface are in human adults is
about 70m2.

Question 10

How does the alveoli maintain a large concentration gradient between the gases in the blood and the alveoli?

Answer 10

The alveoli have a rich blood supply
which circulates and when combined
with the process of ventilation help to
maintain a large concentration
gradient between the gases in the
blood and in the alveoli.

Question 11

what is a thin squashed cell?

Answer 11

Thin squashed cell -

squamous

Question 12

how are the gases in the alveolar air spaces separated from the blood?

Answer 12

The gases in the alveolar air spaces are separated from the blood by the alveolar epithelium (squamous) and the wall of the capillary.

Question 13

Describe the alveolar epithelium

Answer 13

The alveolar epithelium is a
one cell thick layer with a
very thin diffusion distance
to optimise diffusion.

Question 14

describe breathing

Answer 14

Breathing is a result of the difference in pressure between the air in the lungs and the
air outside the body. The pressure inside the lungs is altered by changes in lung volume

Question 15

Describe the process of inhalation.

Answer 15

external intercostal muscles contract                  
Internal intercostal muscles relax 
Rib cage moves outwards
Diaphragm contracts and moves
down
Lung volume increases
Pressure in lungs less than
outside
Air moves into lungs

Question 16

Describe the process of Exhalation.

Answer 16

External intercostal muscles relax
Internal intercostal muscles contract
Rib cage moves inwards
Diaphragm relaxes and moves up
Lung volume decreases
Pressure in lungs greater than outside
Air forced out of lungs

Question 17

Give the equation for pulmonary ventilation

Answer 17

PVR = Tidal volume x breathing rate

Question 18

give the definition of pulmonary ventilation

Answer 18

Pulmonary ventilation (sometimes called minute ventilation) is the amount of air
exchanged in one breathing cycle

Question 19

Give the definition of tidal volume

Answer 19

the volume of air exchanged on one breath

Question 20

Explain how the pulmonary ventilation can be changed

Answer 20

The pulmonary ventilation can be changed by altering either, the ventilation rate, the tidal volume, or both.

Question 21

define inspiratory/exploratory reserve volume

Answer 21

Inspiratory/Expiratory reserve – Extra volume required for a deep breath

Question 22

define residual volume

Answer 22

Residual Volume – Air that remains in lungs to prevent collapse of alveoli.

Question 23

define vital capacity

Answer 23

Vital capacity - is the maximum amount of air a person can expel from the lungs

Question 24

what lung disease causes damage to and scarring of the lung epithelium which results in the
deposition of fibrous tissue in the lung epithelium

Answer 24

Fibrosis

Question 25

name the two effects of fibrosis

Answer 25

1. Reduces the rate of diffusion (longer diffusion pathway and less
   permeable)
2. Reduces the elasticity of the lung therefore breathing out is not as
   efficient