Lung Volumes and Capacities

1. TOPIC 3 – LUNG FUNCTION CONTINUED
Give definitions and values for the majority respiratory volumes and capacities at rest and during exercise
Interpret a spirometer trace
Explain the principles of diffusion and the importance of partial pressure in the process of gaseous exchange
Describe the process of gaseous exchange at (a) the lungs and (b) the tissues and muscles
Describe the effects of training on lung volumes and capacities and gaseous exchange
Explain the importance of carbon dioxide in the control of breathing
Learning Outcomes:
A – Use independent skills to develop an in-depth
understanding of the respiratory centres
role on breathing - CS, CJ, SF, RM, CE
B – Explain important key terms in relation to
lung capacities and volumes – JH, AC, AA
C – Identify the different key terms associated
with lung capacities and volumes – JB, JB, GB
Do Now Task – Draw 2 flow diagrams outlining the
mechanics of breathing in the lungs

2. LUNG VOLUMES AND CAPACITIES
We know we can vary the depth and volume of our breathing and no matter how
hard you try you can never completely empty your lungs of air.
This is a good thing because of the moisture around the alveoli would mean that
they would stick the lungs together and cause them to collapse.
Meaning we have a large amount of air in reserve in our lungs when we are even
produce shallow breaths
Looking at a reading of our lung inspirations and expirations we can then
identify the different volumes and capacities they can hold

3. Tidal Volume – Amount of air breathed in or out per breath
When we exercise what happened to the depth of our
breathing?
Increases
This means the tidal volume also increases as we need to use
what air we have in reserve to provide the body with the
required air.
What does this air include?
Why do we need oxygen?

4. Vital Capacity – Maximum amount of air exhaled after a maximal inspiration
This does not change whether we are breathing shallow or heavy
Vital Capacity can be measured by a simple equation
VC = TV+IRV+ERV
Vital Capacity = Tidal Volume + Inspiratory Reserve Volume + Expiratory Reserve
Volume
Inspiratory Reserve Volume = Maximal amount of air forcibly inspired in addition to
tidal volume
Expiratory Reserve Volume = Maximal amount of air forcibly expired in addition to
tidal volume

5. Residual Volume – Amount of air left in the
lungs after a maximal expiration
Why is there always a residual volume?
Therefore our Total Lung Capacity is everything
put together
TLC = TV + IRV + ERV + RV

6. MINUTE VENTILATION
Bringing air in and out of our lungs is known as ventilation.
Minute ventilation = the amount of air that is moved in and out of the lungs in one minute.
It is a product of our depth of breathing (TV) and the frequency we breath (breaths per
minute).
What can affect our minute ventilation?
Rate can vary from 12-15 to up to 60 per minute
Tidal volumes can also vary from 0.5 litres during quiet breathing to 3 litres
VE = Frequency of breathing x Tidal Volume (ml)

7. Task

8. GAS EXCHANGE
What’s the point in breathing?
Oxygen in the air – lungs – cells around the body
Air is a mixture of gases but what two are important?
Oxygen and Carbon Dioxide
All gases tend to evenly distribute themselves. So if there is a gas
on one side of a semi-permeable membrane in high concentration
and a lower amount on the other side. These gases will naturally
move to equalise themselves.
This process is called?
Diffusion

9. DIFFUSION
Gases can only move from high pressure to low pressure if there is
that pressure distance.
This is called a diffusion gradient.
This movement evenly distributes the molecules until there is no
pressure difference.
No pressure – No gradient – No diffusion
Diffusion is completely dependent on their always being a pressure
gradient

11. DIFFUSION IN THE LUNGS
The walls of the alveoli are semi-permeable therefore allowing the
passage of oxygen and carbon dioxide molecules through it holes.
This concentration of gas is known as partial pressure, which is
the pressure exerted by a single gas in a mixture of gases.
This is measured in mmHg (millimetres of mercury)

12. Diffusion in the
lungs

13. SUMMARY
There are a number of factors that make diffusion of oxygen from
lungs to blood very efficient.
 Permeability of the alveoli and capillary cell walls
 Short distance from alveoli to capillary
 Readiness of haemoglobin to combine with oxygen to form oxyhaemoglobin
 Diffusion gradient caused by partial pressures
 Large surface area of alveoli
 Slow movement of blood through thin narrow capillaries
 Moisture layer enhancing the uptake of oxygen

14. CONTROL OF BREATHING
Respiration is controlled by the respiration centre in a part of the brain known as
the medulla oblongata.
This is located in the brain stem, found between the spinal cord and upper brain.
The respiratory centre controls both the rate of breathing and depth of breathing
using both neural and chemical control.
http://www.youtube.com/watch?v=F0OBkR00OZE

15. WHEN AT REST
There is an inspiratory and expiratory centre.
During normal breathing the inspiratory centre sends nerve
impulses to the diaphragm and intercostal muscles telling them to
contract so we breath in.
After 2 seconds the system stops allowing the above to relax so we
breath out.

16. DURING EXERCISE
Use books to write notes on how there are chemical and
neurological changes within the body to allow for breathing to
increase and deepen
http://www.youtube.com/watch?v=_BFDgTci0ck

17. Chemical Changes

18. Neurological Changes

19. EXAM QUESTIONS
How is ‘breathing rate’ controlled to meet the demands of changing levels of
exercise?
The alveoli provide the lungs with a large surface area for diffusion.
Name two other structural features of the lungs that assist diffusion.

20. ANSWERS
A. (Exercise/movement) - more carbon dioxide
B. Increased acidity/decrease in pH/increase hydrogen ions (in blood)
C. Detected by chemoreceptors
D. (Nerve impulses to) respiratory centre/medulla (of brain)
E. Phrenic nerve
F. Diaphragm/intercostal muscles/sternocleidomastoids/scalene/pectoralis
minor/abdominals
A. Large blood supply;
B. Thin/semi-permeable membrane for
diffusion/one cell thick/walls are thin;
C. Short distance for diffusion;
D. Layer of moisture;
E. Slower blood flow/transit time.