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 so does the diffusion distance, SA and Volume.
The SA:Vol is smaller as the volume increases more than SA

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

Sphere:
SA: 4πr^2
Vol:4/3πr^3

Question 4

SA and Vol of cuboid

Answer 4

SA: 2(bh + bl + hl)
Vol: hbl

Question 5

SA and Vol of cylinder

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

Higher level of activity- more metabolic demands so more oxygen and glucose required.

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 the cells can be supplied.
Some larger organisms have a very small SA:Vol ratio meaning that they cannot get sufficient nutrients by diffusion alone- must adapt to form more specialised exchange surfaces.

Question 8

Suggest some reasons why some organisms need specialised exchange surfaces.

Answer 8

When they have a small SA:Vol ratio diffusion is too slow so they need to have specialised exchange system 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 area needed exchange, overcoming limitations SA:Vol ratio. e.g root hairs, villi
2. Thin layers- shorter distances for substances to diffuse- faster and more efficient e.g. alveoli, villi
3. Good blood supply- steeper conc gradient= faster diffusion. e.g alveoli, gills, villi
4. Ventilation to maintain conc gradient- 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* Conc gradient)/ thickness of barrier (distance)

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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

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

Question 13

Describe the structure of the trachea

Answer 13

1. wide tube supported by incomplete rings of strong flexible cartilage- stop from collapsing
2. Lined with a ciliated epithelium with goblet cells between and below the epithelial cells- secrete mucus onto lining of trachea to trap dust and micorgs that have escaped the nose lining.
3. Cilia beat and move the mucus along with trapped dirt and micorgs away from lungs

Question 14

Describe the structure of the bronchus

Answer 14

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

Question 15

Describe the structure of the bronchioles

Answer 15

1. Bronchi divide to make many small bronchioles.
2. Smaller bronchioles have no cartilage rings
3. Walls of bronchioles contain smooth muscle - when it contracts the bronchioles constrict, when relaxes they dilate. - this changes amount of air reaching the lungs
4. Lined with layer of flattened epithelium - some gaseous exchange can happen.

Question 16

Describe the structure of the alveoli

Answer 16

1. Consist of layer of thin, flattened epithelial cells along with some collagen and elastic fibres- allows the alveoli to stretch as air is drawn in. When they return to resting size air is squeezed out- elastic recoil of lungs
2. Large SA
3. Thin layers- one cell thick
4. Good blood supply- surrounded by capillaries to maintain steep conc gradient.
5. Good ventilation
6. Inner surface is covered by thin layer of solution of water, salts and lung surfactant- surfactant allows alveoli to remain inflated and Oxygen is dissolved in the water before diffusion into the blood

Question 17

Define 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 divide into bronchioles which have alveoli.
two lungs and a diaphragm under them.
ribs over the lungs with intercostal muscles in between

Question 21

Define the term inspiration

Answer 21

Taking air in or inhalation- energy using process

Question 22

Define the term expiration

Answer 22

Normal expiration ( breathing out or exhalation)- passive process

Question 23

Define the term active process

Answer 23

A process which requires energy

Question 24

Define the term passive process

Answer 24

A process which doesn’t require 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 and diaphragm muscles contract
2. This causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax (space where the lungs are)
3. As the volume increases the lung pressure decreases (below atmospheric pressure)
4. This causes air to 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 an diaphragm muscles relax.
2. The ribcage moves downwards and inwards and the diaphragm becomes curved again.
3. The thorax volume decrease, causing air pressure to increase
4. Air is forced out of the lungs down the pressure gradient
5. Normal expiration is passive process
6. Alveoli- elastic recoil

Question 27

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

Answer 27

Expiration can be forced- the internal intercostal muscles contract to pull the ribcage down and in.
This is an active process rather than the passive process of normal expiration.

Question 28

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

Answer 28

1. Peak flow meter- simple- measures the rate at which air can be expelled from the lung.
2. Vitalographs- more sophisticated versions of PFM- tests the amount of air they breathe out and how quickly this is done- forced expiatory volume in 1 second.
3. Spirometer- can be used to measure several different aspects of lung volume

Question 29

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

Answer 29

1. Subject breathes in and out until Oxygen is used up- breathes into a mouth piece which has a tube connected to the oxygen chamber and has nose clips attached
2. The tube has soda lime in it to absorb the CO2
3. As the person breathes in and out the lid of the chamber moves up and down- movements are recorded by pen attached to lid of chamber, this writes on rotating drum creating a spirometer trace.
4. Find online labelling acivity

Question 30

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

Answer 30

Because it can’t measure residual volume- what is already in your lungs- only what is breathed in and out.
Total lung volume measures residual volume and vital capacity

Question 31

Define the the term tidal volume

Answer 31

Is the volume of air that moves into and out of the lungs with each resting breath.

Question 32

Define the the term vital capacity

Answer 32

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

Question 33

Define the the term inspiratory reserve volume

Answer 33

Is the maximum volume of air you can breathe in after normal inhalation.

Question 34

Define the the term expiratory reserve volume

Answer 34

Is the extra volume of air you can force out of your lungs after the normal tidal volume of air you breathe out.

Question 35

Define the the term residual volume

Answer 35

Is the volume of air left in your lungs when you have exhaled as hard as possible- can’t measured directly.

Question 36

Define the the term Total lung capacity

Answer 36

Is the sum of the vital capacity and residual volume- the volume of air in you lungs after maximal inspiration.

Question 37

Define the the term breathing rate

Answer 37

Is the number of breaths taken per minute

Question 38

Define the the term ventilation rate

Answer 38

Is 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

1. Tidal volume- the range between the peak and troughs of normal breathes- all the same size waves
2. Vital capacity- the range form the bottom of the lowest peak to the top of the highest
3. Inspiratory reserve volume- the range from the peak of the smaller waves to the peak of the large waves.
4. Expiratory reserve volume- the range from the trough of the smaller waves to the trough of the larger wave.
5. Residual volume- the range from the trough of the larger waves to 0 on the y-axis
6. Total lung capacity- the total range from 0 to the peak of the 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 graphs- measured in mL
Spirometer trace- measured in volume of gas in spirometer/ dm^3
Changes in lung volume- peaks are for inspiratory and troughs are for expiratory
Spirometer trace- peaks are for expiratory and trough for inspiratory.

Question 41

Explain how to calculate breathing rate from spirometer trace.

Answer 41

1. Count how many peaks there are in tidal volume section of the graph- number of breaths
2. Read off x axis to see the time it took for thast number of breathes
3. Then calculate breathes per minute

Question 42

Explain how to calculate tidal volume from spirometer trace.

Answer 42

Measure from the peak to the trough of the smaller waves.

Question 43

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

Answer 43

Ventilation rate= breathing rate * 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.

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 more oxygen for respiration to provide energy.
The larger the the tidal volume and breathing rate the larger the volume of oxygen uptake- so you need them to be larger when exercising.

Question 46

Suggest why it is not possible to remove all the air from the lungs

Answer 46

The thorax/rib cage/ lungs cannot be completely compressed
The trachea and bronchi are held open by cartilage
Bronchioles/alveoli are held open by elastic fibres

Question 47

Describe how a spirometer can be used to measure tidal volume

Answer 47

1. Don’t breathe through nose
2. Subject breathes evenly
3. Measure amplitude of the waves
4. Measure at least 3 and take the mean
5. As you breathe in the lid and pen move down

Question 48

State the function of the smooth muscle fibres i the bronchus

Answer 48

To constrict the bronchus to control the movement of air

Question 49

Describe the function of the elastic fibres in the alveoli walls

Answer 49

To recoil/ expel air/ prevent bursting