P6 M3
Functions
of the
Respiratory system
• The respiratory system is responsible for:
– getting oxygen in to our body
– Getting carbon dioxide and other waste products out of our body
• All living creatures need Oxygen in
combination with food to produce
energy and movement.
• Every cell of the body needs
Oxygen to function
• Respiration is the process by
which cells receive a constant
supply of oxygen and carbon
dioxide is removed.
• The aim of the respiratory
system is to get:
– Oxygen to the
bloodstream
• so that the CV system can
deliver it to the muscles.
– Carbon dioxide out of the
bloodstream
• All endurance performance relies
on
– Delivery of Oxygen into the
When we exercise: CO2 dissolves within the
blood stream
bloodstream and increases acidity levels. So the
– Removal of Carbon Dioxide
respiratory centre in the brain speeds up the rate
out of the blood
of breathing to get rid of excess CO2.
So rate of breathing increases due to CO2 levels
rising. Not the cells demanding more O2.
• Give a couple of specific
examples in your worksheet
• Gases move through a process called diffusion
– Gas moves from a high concentration to a low
concentration
• Eg: someone wearing perfume.
• In the respiratory system
–Two different types of
diffusion:
• Diffusion of Oxygen into the blood
stream, attracted by haemoglobin
• Diffusion of Carbon Dioxide out of
the blood stream to be excreted
by the lungs
• The alveoli are in constant contact with the
capillaries
• The air we breath in arrives in the alveoli,
rich in Oxygen
• The blood arrives from the pulmonary artery
very low in oxygen
• Following the principle of diffusion, the
Oxygen moves across the capillary wall
and into the blood stream
– It is attracted by the haemoglobin into the
red blood cells
• The blood returns to the heart to be pumped
to the rest of the body
• The blood arrives in capillaries of the lungs with a high concentration
of Carbon Dioxide
• The air in the alveoli has a low concentration of Carbon Dioxide
According to the principles of diffusion, the Carbon dioxide moves
across the wall of the capillaries and into the alveoli, so that it can
be expired.
The mechanics of
breathing
Overview
• Breathing is regulated by:
• the respiratory centre,
located in the brain.
• Receptors in the air
passages and lungs
• Breathing in = Inspiration
• Breathing out = Expiration
• To breathe the thorax must
increase and then decrease in
size
Inspiration
• In order to breathe in the volume of the
chest cavity needs to increase.
• This increase in size of the chest cavity,
causes a decrease in pressure within the
lungs
• Boyle’s Law states that a volume of gas is
inversely proportional to its pressure.
• This means that the increase in volume in
the lungs causes a decrease in pressure.
• Gases flow from a high pressure area to a
low pressure area
• In this situation the ambient air is the high
pressure area and the lungs are the low
pressure area, so the air flows into the
lungs
Inspiration
• Inspiration – Breathing in
• Diaphragm contracts
• It flattens and pulls down
• This is an active process
• External intercostal muscles contract
• The sternum moves up and out, with the • These two actions cause
the volume of the thoracic
lungs following
cavity to increase
• The lungs are attached to the pleural sac
(containing pleural fluid), which in turn is
attached to the thoracic cage
• As the chest expands, the surface
tension, created by the film of pleural
fluid causes the lungs to be pulled
outwards, with the chest
• According to Boyles Law
this increase in volume
causes a decrease in
pressure
• Air flows into the lungs
• As gas flows from high
pressure to low pressure.
Expiration
• To breathe out – Expiration:
• Diaphragm relaxes
• It moves back up and into the thoracic cavity
• This is a passive process
• The external intercostal muscles relax
• The ribs/sternum moves down.
• The lungs, sternum and rib cage are elastic structures that naturally 'spring'
back to their resting positions once the forces of the inspiratory muscles
are removed. So expiration is a passive process.
• The volume of the thoracic cavity decreases causing the air to
move out of the lungs.
• This is because air pressure in the lungs is now higher than atmospheric
pressure, according to Boyles Law, so the air is forced out of the lungs to
equate the pressure in and out of the body.
The muscles of breathing
Respiratory
volumes
Lung Volumes
• Lung volumes: refers to physical differences in lung volume, while
lung capacities represent different combinations of lung volumes,
usually in relation to inhalation and exhalation.
• The average pair of human lungs can hold about 6 litres of air, but
only a small amount of this capacity is used during normal breathing.
Spirometer trace
Respiratory
volumes
• Tidal Volume
– The volume of air inspired
or expired per breath
(Approx 500ml at rest)
• Inspiratory Reserve Volume
– The amount of space that is
available to draw in more air
• Eg; Breathe in normally, then
breathe in more. This extra
capacity is your IRV
• Expiratory Reserve Volume
– The amount of space that is available to breathe out, once you have exhaled
normally
• Eg: Breathe out normally, then force out more air. This is your ERV.
Respiratory
volumes
•
• Residual Volume
– Breathe out as much as
•
possible
• There is always
some air left in
your lungs
• This is your RV
(Approx 1200ml)
Vital Capacity
– Breathe in as much as you can,
and then force as much air out of
your lungs as possible.
• This is your IRV+ERV+TV,
and is your Vital Capacity
Total Lung
Capacity
– Take in as
much breath
as possible
– This is your
total lung
capacity
– ERV+IRV+TV
+RV (Approx
6000ml)
Describe the
(1) Structure with
all the parts named BELOW and
(2)
Function (1-4 BELOW) of the
respiratory system.
1. Structure of the respiratory
system:
•
•
•
•
•
•
•
•
•
•
Nasal cavity
Epiglottis
Pharynx
Larynx
Trachea
Bronchus
Bronchioles
Lungs (lobes, pleural membrane, thoracic cavity,
visceral pleura, pleural fluid, alveoli)
Diaphragm
Intercostal muscles (external and internal)
Examine the respiratory system
explain
and
how it works and
how each part of the system is
designed to meet its function
2. Function:
1. Gaseous exchange
2. Mechanisms of breathing
(inspiration and expiration)
3. Lung volumes: e.g. tidal
volume, vital capacity, residual
volume
4. Control of breathing (neural and
chemical)