1. PHED 1 Applied Physiology Lung Function
AS PE
PHED 1
Applied Physiology
Lung Function

2. Lung Function Learning Objectives
To understand the key terminology of lung function
To be able to explain how inspiration and expiration occur
To understand how these process are effected by physical exercise and training

3. NASAL CAVITY PHARYNX MOUTH TRACHEA RIGHT LUNG BRONCHILOES BRONCHUS
LARYNX (VOICE BOX)
TRACHEA
RIGHT LUNG
BRONCHILOES
BRONCHUS
DIAPHRAGM
ALVEOLI

4. Route of Air through Respiratory System
You will not be examined on the structure of the respiratory system but need to have a basic route of an air particle:
Nasal Cavity
Larynx
Trachea
Bronchus
Bronchioles
Alveoli/Air sacs
structure of respiratory system

5. Mechanics of Breathing
Air moves from areas of high pressure to areas of low pressure.
To breathe in the air pressure in the lungs must be lower than the pressure in the atmosphere.
Atmospheric pressure is 100kPa. When we inspire we lower the air pressure in alveoli to kPa.
This causes air to flow in.

6. Inspiration
During inspiration we lower the air pressure in our lungs by increasing the volume of the lungs.
At rest (quiet breathing) this is done by the diaphragm contracting (flattening) and the intercostal muscles lifting the ribcage up and out.
This is an active process.

7. Expiration When at rest expiration is a passive process.
The intercostal muscles and diaphragm relax.
Volume of thoracic cavity decreases.
Air pressure in the lungs increases.
Air is forced out.

8. Inspiration during Exercise
During exercise both rate and depth of breathing increase.
Inspiration increases through greater expansion of the thoracic cavity.
The amount of air inspired in one breath (tidal volume) can rise from 0.5L to 3.5L.
Breathing rate can rise from breaths per minute to 60.

9. Expiration during Exercise
During exercise expiration becomes an active process.
The intercostal muscles contract to pull the ribcage in and down, whilst the abdominals assist the diaphragm in pushing up.

10. Lung Volumes and Capacities
Volume Name
Description
Value at rest (ml)
Change during exercise
Tidal Volume (TV)
Inspiratory Reserve Volume (IRV)
Expiratory Reserve Volume (ERV)
Vital Capacity (VC)
Residual Volume (RV)
Total Lung Capacity
lung volumes and capacities explained (1.10 onwards)

11. Lung Volumes and Capacities
Volume Name
Description
Value at rest (ml)
Change during exercise
Tidal Volume (TV)
Amount of air breathed in or out per breath
Inspiratory Reserve Volume (IRV)
Maximal amount of air forcibly inspired in addition to tidal volume
Expiratory Reserve Volume (ERV)
Maximal amount of air forcibly expired in addition to tidal volume
Vital Capacity (VC)
Maximal amount of air exhaled after a maximal inspiration
(TV + IRV + ERV)
Residual Volume (RV)
Amount of air left in lungs after a maximal expiration
Total Lung Capacity
Vital capacity plus residual volume
(TV + IRV + ERV + RV)

12. Lung Volumes and Capacities
Volume Name
Description
Value at rest (ml)
Change during exercise
Tidal Volume (TV)
Amount of air breathed in or out per breath
500
Inspiratory Reserve Volume (IRV)
Maximal amount of air forcibly inspired in addition to tidal volume
3100
Expiratory Reserve Volume (ERV)
Maximal amount of air forcibly expired in addition to tidal volume
1200
Vital Capacity (VC)
Maximal amount of air exhaled after a maximal inspiration
(TV + IRV + ERV)
4800
Residual Volume (RV)
Amount of air left in lungs after a maximal expiration
Total Lung Capacity
Vital capacity plus residual volume
(TV + IRV + ERV + RV)
6000

13. Lung Volumes and Capacities
Volume Name
Description
Value at rest (ml)
Change during exercise
Tidal Volume (TV)
Amount of air breathed in or out per breath
500
Increases
Inspiratory Reserve Volume (IRV)
Maximal amount of air forcibly inspired in addition to tidal volume
3100
Decreases
Expiratory Reserve Volume (ERV)
Maximal amount of air forcibly expired in addition to tidal volume
1200
Vital Capacity (VC)
Maximal amount of air exhaled after a maximal inspiration
(TV + IRV + ERV)
4800
Slight increase
Residual Volume (RV)
Amount of air left in lungs after a maximal expiration
None
Total Lung Capacity
Vital capacity plus residual volume
(TV + IRV + ERV + RV)
6000

14. Minute Ventilation (VE)
The amount of air moved in and out of the lungs in one minute.
VE = Breathing Rate x Tidal Volume (ml)
At Rest: VE = 12 x 500ml
= 6 L/min
During Exercise: VE = 60 x 3000ml
= 180 L/min

15. Gas Exchange
Diffusion occurs when gases move from an area of high concentration (partial pressure) to an area of low concentration.
The partial pressure of O2 (PO2)in the alveoli is high, the PO2 in blood returning from the heart to the lungs is low.
O2 diffuses across the semi-permeable alveoli walls into the bloodstream.
It combines with haemoglobin in RBC to form oxyhaemoglobin (oxygenated blood).
The movement of CO2 occurs in exactly the same way but in the opposite direction.

16. Factors Ensuring Efficient Respiratory Diffusion
Permeability of alveoli and capillary cell walls.
Short distance from alveoli to capillary.
Readiness of haemoglobin to combine with O2.
Diffusion gradient caused by different partial pressures.
Large surface area of alveoli.
Slow movement of blood through thin narrow capillaries.

17. Diffusion of O2 in Muscle Cells
O2 diffuses from the oxygenated blood (in capillaries) into muscle cells.
Here in combines with myoglobin to form oxymyoglobin and goes to the mitochondria.
During exercise the muscles use more O2 to create energy. This lowers PO2 in muscle cells, increasing the rate of diffusion.
At the same time more CO2 is produced and so the rate of diffusion of CO2 in the opposite direction increases.

18. How Breathing is Controlled
The rate and depth of breathing is controlled by the medulla oblongata.
During exercise:
Both chemical and neural influences cause an increase in breathing rate and depth.
Chemical changes include:
An increase in CO2 in blood (making it more acidic), and an increase in lactic acid production.
Changes in blood acidity are detected by chemoreceptors.
It is the change in CO2 (and O2) levels that has an affect on respiration.

19. Neural influences include:
Activity from the brain caused by anticipation of exercise.
Increased stimulation from proprioceptors in joints and muscles as a result of physical movements.
Increased body temperature.