Exchange surfaces - Mammalian gas exchange.

Question 1

Describe how diffusion distance, SA, Volume and SA:Vol ratio vary with increasing organism size.

Answer 1

As the organism increases in size the SA and volume increases. However, a large organism has a smaller SA:Vol ratio.

Question 2

State the formulae for the circumference and area of a circle.

Answer 2

Circumference - 2πr

Area - πr^2

Question 3

SA and vol of sphere

Answer 3

SA - 4πr^3

Vol - 4/3(πr^3)

Question 4

SA and vol of rectangular prism.

Answer 4

SA - 2(bh + bl + hl)

Vol - hbl

Question 5

SA and vol of cylindrical prism.

Answer 5

SA - 2πr(r+l)

Vol - πr^2l

Question 6

Describe how the level of activity of an organism is related to demand for oxygen and glucose.

Answer 6

If an organism is v active its cell has very high metabolic demands, meaning requirement loads of oxygen and glucose.

Question 7

Explain how volume is related to demand and surface area is related to supply. Also explain why supply
meeting demand requires adaptations as organisms increase in size.

Answer 7

A high volume means the organism has a lot of cells which all have a metabolic requirement. The larger the SA of the organism, the faster these can be supplied with the necessary nutrients.
Some larger organism have a very small SA:Vol ratio, meaning that they cannot get sufficient nutrients by diffusion alone. They must adapt to form more specialised exchange surfaces.

Question 8

Suggest some reasons why some organisms need specialised exchange surfaces.

Answer 8

• When they a small SA: vol ratio diffusion is too slow to obtain sufficient nutrients so they need to have a specialised exchange system in order to keep up with metabolic demands.

Question 9

State 4 features of efficient exchange surfaces. For each feature explain how it increases efficiency of
the exchange surface.

Answer 9

1) Increased SA - provides SA needed for exchange, overcoming limitations of SA:vol ratio e.g. root hairs, villi.
2) Thin layers - shorter distances for substances to diffuse so it is faster and more efficient e.g. alveoli, villi
3) Good blood supply - steeper concentration gradient = faster diffusion e.g. alveoli, gills. villi
4) Ventilation - maintains concentration gradient so faster diffusion e.g. gills where flow of water carrying dissolved gases, alveoli.

Question 10

State Fick’s law and show how the importance of each of the 4 features of efficient exchange surfaces
can be explained by Fick’s law.

Answer 10

Rate of diffusion is proportional to (SA x Concentration gradient)/ thickness of barrier.

Question 11

Draw and label a diagram of the human gaseous exchange system.

Answer 11

Find online labelling quiz.

Question 12

Describe the structure of the nasal cavity.

Answer 12

• Large SA with good blood supply which warms air to body temperature.
• Hairy lining which secretes mucus to trap dust and bacteria, protecting delicate lung tissue from infection.
• Moist surfaces increase humidity of incoming air, reducing evaporation from exchange surfaces.

Question 13

Describe the structure of the trachea.

Answer 13

• Wide tube supported by incomplete rings of strong flexible cartilage. Stops it from collapsing.
• Lined with a ciliated epithelium with goblet cells between and below the epithelial cells.
• Goblet cells secrete mucus onto lining of trachea to trap dust and microorganisms that have escaped the nose lining.
• Cilia beat and move the mucus along with trapped dirt and microorganisms away from lungs.

Question 14

Describe the structure of the bronchus.

Answer 14

• The trachea divides to form bronchi, each leading to a lung.
• Similar in structure to trachea with same supporting rings of cartilage.

Question 15

Describe the structure of the bronchioles.

Answer 15

• Bronchi divide to make many small bronchioles
• Smaller bronchioles have no cartilage rings
• Walls of bronchioles contain smooth muscle, when it contracts the bronchioles constrict. When it relaxes they dilate.
• This changes the amount of air reaching the lungs.
• They are lined with a layer of flattened epithelium so some gaseous exchange can happen.

Question 16

Describe the structure of the alveoli.

Answer 16

• Consist of layer of thin. flattened layer of epithelial cells along with some collagen and elastic fibres. This allows the alveoli to stretch as air is drawn in. When they return to resting size is squeezed out. This is called the elastic recoil of lungs.
• They have a large SA
• Thin layers, only one cell thick
• Good blood supply, surrounded by capillaries to maintain steep concentration gradient.
• Good ventilation.
• Inner surface is covered by thin layer of solution of water, salts and lung surfactant allows alveoli to remain inflated and oxygen is dissolved in the water before diffusing into the blood stream.

Question 17

Define the term breathing.

Answer 17

A behaviour that you do by muscle contraction and relaxation.

Question 18

Define ventilation.

Answer 18

The air flow generated by breathing. Inhalation/exhalation.

Question 19

Define gas exchange.

Answer 19

The diffusion of gases from an area of higher concentration to an area of lower concentration, especially the exchange of oxygen and carbon dioxide between an organism and its environment.

Question 20

Draw and label a diagram showing the arrangement of the structures involved in breathing.

Answer 20

Trachea divides into bronchi, which then branch off into bronchioles which end in alveoli.
Two lungs and a diaphragm under the lungs.
Ribs over the lungs with intercostal muscles between them.
- Do an online labelling exercise-

Question 21

Define the term inspiration.

Answer 21

Taking air in or inhalation. Active (energy-using) process.

Question 22

Define the term expiration.

Answer 22

Normal expiration (breathing out or exhalation) is a passive process.

Question 23

Define the term active process.

Answer 23

A process that uses energy.

Question 24

Define the term passive process.

Answer 24

A process that does not use energy.

Question 25

Describe the process of inspiration linking the action of muscles, to the movement of structures, the
change in pressure within the lungs and the direction of airflow

Answer 25

1) The external intercostal muscles and diaphragm contract.
2) This causes the rib cage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax.
3) As the volume of the thorax increases the lung pressure decreases (to below atmospheric pressure).
4) This causes air flow into the lungs
5) Inspiration is an active process.

Question 26

Describe the process of normal expiration linking the action of muscles, to the movement of structures,
the change in pressure within the lungs and the direction of airflow.

Answer 26

1) The external intercostal and diaphragm muscles relax.
2) The ribcage moves downwards and inwards and the diaphragm becomes curved again.
3) The thorax volume decreases, causing the air pressure to increase (to above atmospheric pressure).
4) Air is forced out of the lungs.
5) Normal expiration is a passive process.

Question 27

Describe how the process of forced expiration is different from normal expiration and suggest when it
might be used.

Answer 27

During forced expiration, the internal intercostal muscles contract, pulling the rib cage down and in, making it an active process instead of a passive one.
It could be used during intense exercise, the increases the speed of gas exchange.

Question 28

State 3 pieces of equipment used to measure the functioning of the lungs. For each outline how they
work

Answer 28

1) A peak flow meter - simple, measure the rate at which air can be expelled from the lungs.
2) A vitalograph - a more sophisticated version of a peak flow meter. Tests the amount of air they breathe out and how quickly this is done. Measure forced expiatory volume in 1 sec.
3) Spirometer - can be used to measure several different aspects of a lung volume.

Question 29

Label a diagram of a spirometer and annotate with the function of each component

Answer 29

• Subject breathes in and out until O2 is used up. They breathe into a tube connected to the oxygen chamber, wearing a nose clip.
• The tube the subject breathes into has a soda lime in it to absorb carbon dioxide.
• As the person breathes in and out the lid of the chamber moves up and down. These movements are recorded by a pen attached to the lid of the chamber.
• This writes on a rotating drum, creating a spirometer trace.
• Do an online labelling exercise -

Question 30

Describe how a spirometer measures change in lung volume and explain why it cannot measure
total lung volume.

Answer 30

The spirometer cannot measure residual volume (the volume of air left in your lungs after you have exhaled as much as possible), it only measure what you actually breathe out.
Total lung volume includes residual volume so it cannot be measured with a spirometer.

Question 31

Define the term tidal volume.

Answer 31

The volume of air that moves into and out of the lungs with each resting breathing.

Question 32

Define the term vital capacity.

Answer 32

The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible breath.

Question 33

Define the term inspiratory reverse volume.

Answer 33

The maximum volume of air you can breath in after normal inhalation.

Question 34

Define the term expiratory reverse volume.

Answer 34

Volume of air you breathe out after normal exhalation.

Question 35

Define the term residual volume.

Answer 35

The volume of air left in your lungs after you have exhaled as much as possible. Cannot be measure directly.

Question 36

Define the term total lung capacity.

Answer 36

The sum of the vital capacity and residual volume. The maximum amount of air in your lungs after maximal inspiration.

Question 37

Define the term breathing rate.

Answer 37

The number of breaths taken per minute.

Question 38

Define the term ventilation rate.

Answer 38

The total volume of air inhaled in one minute.

Question 39

Label a graph of lung volume during breathing with “tidal volume”, “vital capacity”, “inspiratory reserve
volume”, “expiratory reserve volume”, “residual volume”, and “total lung capacity”.

Answer 39

Tidal volume - the range between the peak and troughs of normal breaths, tend to be all a similar size.
Vital Capacity - the range from the bottom of the lowest peak to the top of the highest.
Inspiratory reverse volume - the range from the peak of the smaller waves to the peak of the larger waves.
Expiratory reverse volume - the range from the peak of the smaller wave to the trough of the larger wave.
Residual volume - the range from the trough of the larger waves to 0 on the y-axis.
Total lung capacity - the total range from 0 to the peak of large waves.

Question 40

Explain how a spirometer trace is different to a graph of the changes in lung volume during breathing.

Answer 40

Changes in lung volume graph - measured in mL
Spirometer traces - measured in volume of gas in spiroemeter dm^3.
Changes in lung volume - peaks are for inspiratory and troughs are for expiratory.
Spirometer trace - peaks are for expiratory and troughs for inspiratory.

Question 41

Explain how to calculate breathing rate and tidal volume from spirometer trace.

Answer 41

1) count how many peaks there are in the tidal volume section of the graph.
2) This will give you the number of breaths.
3) Read off the x-axis to see the time if took for that number of breaths.
4) You can then calculate breaths per minute.

Question 42

Explain how to calculate tidal volume from spirometer trace.

Answer 42

1) Measure peak to trough on the tidal volume waves.

2) Find an average of the values you get for each one.

Question 43

Write an equation to link ventilation rate with breathing rate and tidal volume.

Answer 43

Ventilation rate = breathing rate x tidal volume.

Question 44

Describe how a spirometer trace would differ during exercise as compared to the trace before exercise
started.

Answer 44

The horizontal distance from peak to peak is shorter.

The vertical distance between peak to trough is larger.

Question 45

Describe how tidal volume and breathing rate link to oxygen uptake and explain the importance of the
change in tidal volume and breathing rate during exercise.

Answer 45

When you are exercising you need a larger volume of oxygen for respiration to provide energy.
The larger the tidal volume and the faster the breathing rate, the volume of oxygen uptake will be larger - so you need them to be larger when you’re exercising.