Lung Function
Learning Objectives
1. To understand the key terminology of
lung function
2. To be able to explain how inspiration
and expiration occur
3. To understand how these process are
effected by physical exercise and
training
NASAL CAVITY
MOUTH
PHARYNX
LARYNX (VOICE
BOX)
TRACHEA
RIGHT LUNG
BRONCHILOES
BRONCHUS
DIAPHRAGM
ALVEOLI
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
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
99.74kPa.
 This causes air to flow in.

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.

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.

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 12-15
breaths per minute to 60.

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.

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)
Lung Volumes and Capacities
Volume Name
Description
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
Value at rest
(ml)
Change during
exercise
Lung Volumes and Capacities
Volume Name
Description
Value at rest
(ml)
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
1200
Total Lung Capacity
Vital capacity plus residual
volume
6000
Change during
exercise
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
Decreases
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
1200
None
Total Lung Capacity
Vital capacity plus residual
volume
6000
None
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
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.

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.

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.

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.

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.