Gas Exchange
Week 4
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Daltons Law
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The partial pressures of the 4 gases add
up to 760mm Hg.
Dalton’s Law; in a mixture if gases, the
total pressure equals the sum of the pa
partial pressures exerted by each gas.
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Important Point
• Gases in our bodies are dissolved in
fluids, such as blood plasma.
• According to Henry’s law,
– gases dissolve in liquids in proportion to their
partial pressures, depending also on their
solubilities in the specific fluids and on the
temperature.
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The Site of Gas Exchange
• External Respiration
•
•
CO2 diffuses from pulmonary
capillaries into alveoli
O2 Diffuses from alveoli into
pulmonary capillaries
•Internal respiration
•O2 diffuses from systemic capillaries into
cells
•CO2 diffuses from cells into systemic
capillaries
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Factors Influencing External
Respiration
•
Efficient external
respiration depends on
3 main factors
1) Surface area and
structure of the
respiratory membrane
2) Partial Pressure
gradients
3) Matching alveolar
airflow to pulmonary
capillary blood flow.
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Important Point
• Partial pressure gradients affect gas
exchange between the alveoli and
pulmonary capillaries.
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External respiration: Partial
Pressures
•
The Partial pressures of
gases in the alveoli differ
from those in the
atmosphere.
1) Humidification of inhaled
air
2) Gas exchange between
alveoli and pulmonary
capillaries
3) Mixing of new and old air
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Oxygen Loading
• Oxygen diffuses
along its partial
pressure gradient,
from the alveolus into
the blood, until
equilibrium is reached
• Equilibrium is reached
within the first third of
the capillary.
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Oxygen Loading
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Carbon Dioxide Uploading
• Carbon dioxide
diffuses along its
partial pressure
gradient, from the
blood into the
alveolus, until
equilibrium is reached
• Equilibrium is reached
within the first 4
4/10’s of the capillary
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This Occurs Simultaneously
•Carbon dioxide is very
soluble in blood, allowing
many molecules to diffuse
along this small pressure
gradient.
•Oxygen is less soluble,
requiring a larger
concentration gradient.
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Other Factors Affecting External
Respiration
1) Matching alveolar airflow to pulmonary
capillary blood flow.
2) Watch the following clip.
3) This is Know as the Ventilation-Perfusion
Coupling
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Internal Respiration
• Internal Respiration
• O2 diffuses from
systemic capillaries
into cells
• CO2 diffuses from
cells into systemic
capillaries.
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Internal Respiration Depends on:
1) Available surface
area, which varies in
different tissues.
2) Partial Pressure
gradients
3) Rate of blood flow
varies (e.g.
metabolic rate of
tissue)
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Internal Respiration CO2 and O2
Exchange
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Summary
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AS Level Sport and Physical Education
Please complete the questions on a separate sheet of paper.
Respiratory Exam Questions
1) Describe the anatomical structures involved in pulmonary ventilation. (5
marks)
2) Identify the muscles associated with breathing and their function in pulmonary
ventilation
a) at rest (3 marks)
b) during exercise (3 marks)
3) What are the partial pressures of oxygen and carbon dioxide in inspired air,
alveolar air and arterial and mixed venous blood?
(4 marks)
4) In what forms are oxygen and carbon dioxide transported in the blood? (3 marks)
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Introduction to the Respiratory
System
Review of the Structures Involved in
Breathing
Week 3
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Lets start by reviewing the anatomical
structures of the respiratory system
Can anyone name any of the
structures involved in breathing?
Now we’ve got a list can you put them in order?
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Overview of the Structures of the Respiratory System
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The air continues into many
branching airways known as
the bronchial tree
The trachea and bronchi
have supporting
cartilage to keep the
airways open
Bronchiole walls
contain more
smooth muscle.
The air is moistened,
warmed and filtered as
it flows through these
passageways
The airways from the nasal
cavity through the terminal
bronchioles are called the
conducting zone
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The air then reaches
the respiratory zone
The respiratory zone
The respiratory zone
contains alveoli, tiny
thin walled sacs
where gas exchanges
occurs.
Terminal
bronchi
Alveoli
Lets now look at the
actual site of diffusion,
the respiratory
membrane
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The structure of the respiratory membrane
nIs composed of.
The alveolar wall,
t
The capillary wall,
and,
t
Their basement
membranes.
t
nIt is very thin, measuring
only 0.5 to 4.0 Цm.
nThis membrane presents a
barrier for gas exchange.
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Summary
• The respiratory system consists of the nose,
pharynx, larynx, trachea, bronchi and lungs.
• The lungs contain the bronchial tree, the
branching airways from the primary bronchi
through the terminal bronchioles.
• The respiratory zone of the lungs is the
region containing alveoli, tiny thin-walled sacs
where gas exchange occurs.
• Oxygen and carbon dioxide diffuse between
the alveoli and the pulmonary capillaries
across the very thin respiratory membrane.
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Pulmonary
Ventilation
Week 3
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Pulmonary Ventilation
Pulmonary ventilation, or
breathing, is the
exchange of air between
the atmosphere and the
lungs.
As air moves into and
out of the lungs, it
travels from regions of
high pressure to
regions of low
pressure.
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Boyle’s Law – the relationship
between pressure and volume
In this smaller
larger volume,
sphere the
the gas
molecules
molecules
strike
the walls
strike
more
the wall
frequently,
lessmolecules
thus
Pressure
is caused
by gas
frequently,
increasing
pressure.
thus
exerting
less
striking the
walls
of a container.
The
pressure.
pressure is related to the volume of
the container
Boyle’s Law: The pressure of a
gas is inversely proportional to the
volume of its container. Increasing
volume decreases pressure,
decreasing volume increases
pressure
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Quiet Breathing
During quiet inspiration, the
diaphragm and the external
intercostal muscles contract.
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Inspiration
Increasing the volume
What does
decreases the pressure
this the
do???
within
thoracic cavity
and the lungs.
Quiet Breathing
Expiration
Quiet expiration is a passive process, in
which the diaphragm and the external
intercostals muscles relax,and the elastic
lungs and thoracic wall recoil inward.
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This decreases the
volume and therefore
increases the
pressure in the
thoracic cavity.
Deep or Forced Breathing
Deep breathing uses forceful contractions of the inspiratory
muscles and additional accessory muscles to produce larger
changes in the volume of the thoracic cavity during both
inspiration and expiration.
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Intrapulmonary Pressure Changes
Intrapulmonary
press is the
pressure within the
alveoli.
Between breaths, it equals
atmospheric pressure
(760mm Hg)
Inspiration
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Expiration
Lets Recap Inspiration
Diaphragm and external
intercostals contract
Volume of thoracic
cavity increases
Lungs expand
Intrapulmonary pressure
becomes negative
Air flows into the lungs
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Lets Recap Expiration
Diaphragm and external
intercostal muscles relax
Volume of the thoracic
cavity decreases
Lungs recoil
Intrapulmonary pressure rises
above atmospheric pressure
Air flows out of the lungs
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Other Factors Affecting
Ventilation
Resistance
As air flows into the lungs, the
gas molecules encounter
resistance when they strike
the walls of the airway.
Therefore the diameter of the
airways affects resistance.
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Lung Compliance
The ease which the lungs
expand is called lung
compliance.
Summary
• Muscle activity causes changes in the
volume of the thoracic cavity during
breathing.
• Changing the thoracic cavity volume
causes intrapulmonary changes, which
allow air to move from high pressure to
low pressure regions.
• Lung Compliance and Resistance affect
ventilation.
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Who wants to be a
millionaire
To start the game click here
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Wrong !!!!!
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£100 Question
• What is the respiratory system?
a)
b)
c)
d)
The
The
The
The
body's
body's
body's
body's
breathing system
system of nerves
food-processing system
blood-transporting system
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£200 Question
•
a)
b)
c)
d)
What is the purpose of the little hairs
inside the nose?
To fight disease.
They serve no purpose.
To keep dust out of the lungs.
To tickle the nose and cause sneezes.
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£400 Question
• What is another
name for the
windpipe?
a) Lungs
b) Larynx
c) Trachea
d) Oesophagus
Audience
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Fifty Fifty
• What is another name for the windpipe?
b) Larynx
d) Oesophagus
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£1000 Question
•
a)
b)
c)
d)
What is the
primary waste gas
diffused out of the
blood into the
alveoli?
Carbon dioxide
Oxygen
Methane
Ammonia
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Fifty / Fifty £1000
• What is the primary waste gas diffused
out of the blood into the alveoli?
a)Carbon dioxide
b)Methane
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£2000
•
a)
b)
c)
d)
What is the anatomical term for the
voice box?
Pharynx
Bronchi
Trachea
Larynx
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Fifty / Fifty £2000
• What is the anatomical term for the
voice box?
a)Pharynx
b)Larynx
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£4000
•
a)
b)
c)
d)
What are the tiny clusters of
chambers for diffusion of gases in the
lungs?
Alveolar Sacs
Lobes
Pleura
Bronchioles
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Fifty / Fifty 4000
• What are the tiny clusters of chambers
for diffusion of gases in the lungs?
a)Alveolar Sacs
b)Bronchioles
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£8000
•
a)
b)
c)
d)
What is the name of the division
between the middle and lower lobes of
the right lung?
Oblique fissure
Pleura
Median Sulcus
Sagittial Suture
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Fifty / Fifty 8000
• What is the name of the division
between the middle and lower lobes of
the right lung?
a)Oblique fissure
b)Pleura
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£16000
•
a)
b)
c)
d)
The lungs contain how many lobes in
total?
3
5
2
4
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Fifty / Fifty 16000
• The lungs contain how many lobes in
total?
a)3
b)5
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£32000
•
a)
b)
c)
d)
What encloses the lungs and protects
the lobes from friction against the
thorax?
Diaphragm
Myelin Sheath
Pericardium
Pleura
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Fifty / Fifty £32000
• What encloses the lungs and protects
the lobes from friction against the
thorax?
a)Myelin Sheath
b)Pleura
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£64000
The airways from the nasal cavity through
the terminal bronchioles are called the?
a) conducting zone
b) Respiratory zone
c) respiratory membrane
d) alveolar wall
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Fifty / Fifty 64000
The airways from the nasal cavity through
the terminal bronchioles are called the?
a) conducting zone
b) Respiratory zone
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125000
•
a)
b)
c)
d)
Name the fluid found between the
alveolus and pulmonary capillary.
Mucus
Visceral pleurae fluid
Parietal Pleurae fluid
Interstitial fluid
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50 / 50 125000
• Name the fluid found between the
alveolus and pulmonary capillary.
a)Visceral pleurae fluid
b)Interstitial fluid
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£50000
• Name the cells within the alveoli where
diffusion actually occurs.
a) Alveolar Macrophage
b) Simple squamous epithelium
c) Surfactant secreting cells
d) Capillary
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50000 50 / 50
• Name the cells within the alveoli where
diffusion actually occurs.
a)
b) Simple squamous epithelium
c) Surfactant secreting cells
d)
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£1 million
•
a)
b)
c)
d)
Roughly what is the total service area
of the alveoli?
Football Pitch
4 Desk tops
2 Frying Pan
3 badminton courts
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50 / 50 1 million
• Roughly what is the total service area
of the alveoli?
a)2 Frying Pan
b)3 badminton courts
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Ventilation
Lung Volumes
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Did You Know?
• The lung volume of the
average male resting is 3
litres.
• Normal inspiration
increases this volume by
half a litre.
• Forced maximum
inspiration raises the
volume to 6 litres.
• Forced maximum
expiration lowers the
volume to 1 litre.
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The Type of Lung Volume
• The total lung capacity is calculated by adding
the vital capacity of the lungs to the residual
volume:
• Lets now look at the types of lung volume. You
need to know this as we will be looking at
spirographs soon (which will be on your exam).
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Vital Capacity
• The largest volume of air that can
be expired (maximum expiration)
after a maximum inspiration.
• VC is made up of components we
will look at them shortly.
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Residual Volume
• The volume of air that
remains in the lungs after
forced maximum expiration.
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Types of Lung Volume
• The vital capacity figure
takes into account such
factor as:
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Tidal Volume
• The amount of air inspired and
expired with each normal breath
at rest or during any stated
activity.
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Inspiratory Reserve Volume
• The volume able to be
inspired, during forced
inspiration, after quiet
inspiration.
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Expiratory Reserve Volume
• The volume able to expired,
forced expiration, after quiet
expiration.
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Therefore:
• Total lung capacity = vital capacity +
residual volume.
= Tidal volume + inspiratory reserve
volume + expiratory reserve volume +
residual volume.
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Bit of an Aside
• Lung volume figures are not particularly
important in determining athletic performance.
• What is more important is the efficiency of the
exchange of oxygen and carbon dioxide
between the lungs and the blood, and between
the blood and the muscle fibres.
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Bit of an Aside
• Smoking interferes with lung volumes. The
irritation from tobacco smoke causes mucous
secretion which narrows the air passages. One
cigarette can reduce the vital capacity of the
lungs by 10 – 15 %.
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Ventilation
• Ventilation is the amount
of air breathed in one
minute.
• It can be defined by this
equation:
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• Ventilation =
Tidal volume x respiratory
rate
• Normal =
0.5 litres x 12 breaths/min
= 6 litres per minute.
Respiratory Volumes
Average Respiratory Volumes for a 20 year- old male
3500
3100
3000
Milli Litres
2500
2000
1500
1200
1200
1000
500
500
0
Tidal Volume
Inspiratory Reserve Volume
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Expiratory Reserve Volume
Residual Volume
Homework
Please complete these questions and hand
back to me in next lesson.
1) The lungs have no skeletal tissue, so how do they increase in size
on breathing in?
2) Identify the major vascular substances that determine the amount
of oxygen that can be delivered to body tissues and explain how it
functions.
3) Describe how alveolar ventilation changes during exercise.
4) What three factors affect oxygen dissociation during exercise and
how?
5) Describe the relationships between haemoglobin, pO2, acidity,
pCO2 and temperature.
6) Explain how CO2 is picked up by the tissue capillary blood and
then released into the alveoli.
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Transport of Oxygen and
Carbon Dioxide
How Gases Are Transported
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Introduction
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Goals For Learning
• To explore how O2 is
transported in the
blood.
• To explore how Co2
is transported in the
blood.
• This will include
understanding the
oxygen dissociation
curve.
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• What you need to
know
• Definition of partial
pressure
• Processes of external
respiration and
internal respiration.
Oxygen Transport
• O2 is transported by the blood either,
– Combined with haemoglobin (Hb) in the red blood
cells (>98%) or,
– Dissolved in the blood plasma (<2%).
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Oxygen Transport
• The resting body requires 250ml of O2 per
minute.
• We have four to six billion haemoglobin
containing red blood cells.
• The haemoglobin allows nearly 70 times
more O2 than dissolved in plasma.
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Haemoglobin
Haemoglobin molecules can
transport up to four O2’s
When 4 O2’s are bound to
haemoglobin, it is 100% saturated,
with fewer O2’s it is partially
saturated.
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Co-operative binding:
haemoglobin’s affinity for
O2 increases as its
saturation increases.
Oxygen binding occurs in
response to the high PO2 in the
lungs
Lets Now Look at Haemoglobin
Saturation
• Haemoglobin saturation is the
amount of oxygen bound by
each molecule of haemoglobin
• Each molecule of haemoglobin can carry four
molecules of O2.
• When oxygen binds to haemoglobin, it forms
OXYHAEMOGLOBIN;
• Haemoglobin that is not bound to oxygen is
referred to as DEOXYHAEMOGLOBIN.
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Haemoglobin Saturation
• The binding of O2 to haemoglobin depends
on the PO2 in the blood and the
bonding strength, or affinity, between
haemoglobin and oxygen.
• The graph on the following page shows an
oxygen dissociation curve, which reveals
the amount of haemoglobin saturation at
different PO2 values.
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The Oxygen Dissociation Curve
• Reveals the amount of
haemoglobin saturation
at different PO2 values.
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The Oxygen Disassociation Curve
Haemoglobin saturation isIn the lungs the partial
pressure is approximately
determined by the partial pressure
100mm of
Hg at this Partial
haemoglobin has
oxygen. When these values Pressure
are
a high affinity to 02 and is
98% saturated.
graphed they produce the Oxygen
Disassociation Curve
In the tissues of other
organs a typical PO2 is 40
mmHg here haemoglobin
has a lower affinity for O2
and releases some but not
all of its O2 to the tissues.
When haemoglobin leaves
the tissues it is still 75%
saturated.
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Haemoglobin Saturation at High Values
Lungs at sea level:
PO2 of 100mmHg
haemoglobin is 98%
SATURATED
When the PO2 in the
lungs declines below
typical sea level values,
haemoglobin still has a
high affinity for O2 and
remains almost fully
saturated.
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Lungs at high
elevations: PO2
of 80mmHg,
haemoglobin 95
% saturated
Even though PO2
differs by 20 mmHg
there is almost no
difference in
haemoglobin
saturation.
Haemoglobin Saturation at Low Values
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Factors Altering Haemoglobin
Saturation
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Factors Altering Haemoglobin
Saturation (Exercise)
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Factors Affecting Haemoglobin
Saturation
• Blood acidity…
• Blood temperature…
• Carbon Dioxide concentration
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Respiratory Response to Exercise
Factors affecting Disassociation
BLOOD TEMPERATURE
• increased blood temperature
• reduces haemoglobin affinity for O2
• hence more O2 is delivered to warmed-up
tissue
BLOOD Ph
• lowering of blood pH (making blood
more acidic)
• caused by presence of H+ ions from lactic
acid or carbonic acid
• reduces affinity of Hb for O2
• and more O2 is delivered to acidic sites
which are working harder
CARBON DIOXIDE CONCENTRATION
• the higher CO2 concentration in tissue
• the less the affinity of Hb for O2
• so the harder the tissue is working, the
more O2 is released
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Key Point
• Increased temperature and hydrogen ion
(H+) (pH) concentration in exercising
muscle affect the oxygen dissociation
curve, allowing more oxygen to be
uploaded to supply the active muscles.
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Carbon Dioxide Transport
• Carbon dioxide also relies on the blood fro
transportation. Once carbon dioxide is
released from the cells, it is carried in the
blood primarily in three ways…
• Dissolved in plasma,
• As bicarbonate ions resulting from the
dissociation of carbonic acid,
• Bound to haemoglobin.
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Dissolved Carbon Dioxide
• Part of the carbon dioxide released from the
tissues is dissolved in plasma. But only a small
amount, typically just 7 – 10%, is transported
this way.
• This dissolved carbon dioxide comes out of
solution where the PCO2 is low, such as in the
lungs.
• There it diffuses out of the capillaries into the
alveoli to be exhaled.
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In Review
1) Oxygen is transported in the blood primarily
bound to haemoglobin though a small amount
is dissolved in blood plasma.
2) Haemoglobin oxygen saturation decreases.
1)
2)
3)
When PO2 decreases.
When pH decreases.
When temperature increases.
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In Review
Each of these conditions can reflect increased
local oxygen demand. They increase oxygen
uploading in the needy area.
3) Haemoglobin is usually about 98% saturated
with oxygen. This reflects a much higher
oxygen content than our body requires, so the
blood’s oxygen-carrying capacity seldom limits
performance.
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In Review
4) Carbon dioxide is transported in the blood
primarily as bicarbonate ion. This
prevents the formation of carbonic acid,
which can cause H+ to accumulate,
decreasing the pH. Smaller amounts of
carbon dioxide are carried either
dissolved in the plasma or bound to
haemoglobin
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Gas Exchange at the Muscles
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Gas Exchange at the Muscles
• Now we have considered how our respiratory
and cardio-vascular system brings air into our
lungs, exchange oxygen and carbon dioxide in
the alveoli, and transport oxygen to the muscles
(and CO2 away from them).
• All that remains is for us to consider the delivery
of oxygen to the muscles from the capillary
blood.
• This gas exchange between the tissue and the
blood in the capillaries is known as – internal
respiration.
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The Arterial-venous Oxygen
Difference
• At rest, the oxygen content of arterial blood is
about 20ml of oxygen per 100 ml of blood.
• This value drops to 15 or 16ml of O2 per 100ml
as the blood passes through the capillaries into
the venous system.
• This difference in oxygen content
between arterial and venous blood
is referred to as the arterial-venous
oxygen difference (a-VO2diff).
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ARTERIOVENOUS OXYGEN DIFFERENCE
a-vO2 diff
• this expresses the difference between the oxygen carried by
blood in arteries and veins
• and represents the amount of oxygen delivered to working
tissue in the capillary system
venule
a-vO2 diff - AT REST
capillary
15ml O2
per 100ml blood
a-vO2 diff = 5ml
per 100ml blood
arteriole
20ml O2
per 100ml blood
a-vO2 diff - DURING INTENSE EXERCISE
venule
capillary
arteriole
5ml O2
per 100ml blood
a-vO2 diff = 15ml
per 100ml blood
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blood flow
20ml O2
per 100ml blood
blood flow
The Arterial-venous Oxygen
Difference
• It reflects the 4-5 ml of oxygen per 100 ml
of blood taken up by the tissues.
• The amount of oxygen taken up is
proportional to its use for oxidative energy
production. Thus as the rate of oxygen
use increases, the a-vO2 diff also
increases.
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The Arterial-venous Oxygen
Difference
• E.g. during intense
exercise the a-vO2 diff in
contracting muscles can
increase to 15 to 16 ml
per 100ml of blood.
During such an effort, the
blood unloads more
oxygen to the active
muscles because the
PO2 in the muscles is
drastically lower than
in arterial blood.
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Key Point
• The a-vO2 diff increases from a resting
value of about 4 to 5 ml per 100 ml of
blood up to values of 15 to 16 ml per 100
ml of blood during exercise.
• This increase reflects an increase
extraction of oxygen from arterial blood by
active muscle, thus decreasing the oxygen
content of the venous blood.
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Factors Influencing Oxygen
Delivery and Uptake.
• The rates of oxygen delivery and uptake depend
on the three major variables.
• The oxygen content of blood.
• The amount of blood flow.
• The local conditions.
• As we begin to exercise, each of these variables
must be adjusted to ensure increased oxygen
delivery to our active muscles.
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Factors Influencing Oxygen
Delivery and Uptake.
• We have discussed in class that under
normal circumstances haemoglobin is
98% saturated with oxygen.
• Any reduction in the blood’s normal
oxygen carrying capacity would hinder
oxygen delivery and reduce cellular uptake
of oxygen.
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Factors Influencing Oxygen
Delivery and Uptake.
• Exercise causes increased blood flow
through the muscles. As more blood
carries oxygen through the muscles, less
oxygen must be removed from each 100
ml of blood (assuming the demand
remains unchanged).
• Thus increasing blood flow improves
oxygen delivery and uptake.
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Factors Influencing Oxygen
Delivery and Uptake.
• Many local changes in the muscle during
exercise affect oxygen delivery and uptake.
• Muscle activity increases muscle acidity
because of lactate production.
• Muscle temperature and carbon dioxide
concentration both increase because of
increased metabolism.
• All of these increase oxygen uploading from
haemoglobin molecule, facilitating oxygen
delivery and uptake by the muscles.
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Factors Influencing Oxygen
Delivery and Uptake.
• During maximal exercise,however, when
we push our bodies to the limit, changes in
any of these areas can impair oxygen
delivery and restrict out abilities to meet
oxidative demands.
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The Respiratory System
External and Internal Respiration
Learning Objectives
nHow gases move into and out of the body (external respiration).
nHow gases move within the body (internal respiration).
nAn understanding of partial pressure.
nThe relationship between partial pressure and movement of gases within the body.
Introduction
Introduction
nThe respiratory and cardiovascular system combine to provide an efficient delivery system.
uCarries oxygen (O2) to body tissues.
uRemoves (CO 2).
nThis transport system involves four separate process….
Transportation
nPulmonary ventilation (breathing).
nPulmonary diffusion.
nTransport of oxygen and carbon dioxide via blood.
nCapillary gas exchange.
Pulmonary Ventilation
nCommonly referred to as breathing.
nIt is the process by which air moves in and out of the lungs.
Pulmonary Ventilation
nAir is typically drawn into the lungs through the nose.
nThe mouth can be used.
nBring air in through the nose has advantages over mouth breathing.
uAir is warmed and humidified.
uDust and other particles can be filtered out.
Pulmonary Ventilation (Transport Summary)
nIn through nose and mouth.
nDown the pharynx.
nDown the larynx.
nThrough the trachea.
nThrough the bronchi.
nThrough the bronchioles.
nThen reaches the sites of gas exchange the alveoli.
Pulmonary Ventilation
Inspiration
Inspiration
nInspiration is…
tAn active process.
tInvolving the diaphragm and the external intercostals.
nThe ribs and sternum are moved by the external intercostals muscles.
tThe ribs swing up and out.
tThe sternum swings up and forward.
tAt the same time the diaphragm contracts.
Inspiration
nThese actions expand all three dimensions of the thoracic cage.
uIn tern this expands the lungs.
nThis action reduces the air pressure in the lungs (intrapulmonary pressure).
uThis is less than the pressure outside the body.
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nAir rushes into the lungs to reduce the pressure difference.
is brought into the lungs during inspiration.
uThus air
Exercise and Inspiration
nDuring forced or laboured breathing – as in exercise, inspiration is further assisted by,
uOther muscles such as scalenes (anterior, middle and posterior).
uSternocleidomastoid (in the neck).
uPectorals.
nThese help raise the ribs even more than during regular breathing.
Inspiration
nThe pressure changes required for adequate ventilation at rest are really quite small. For example, at
standard atmospheric pressure (760mmHg), inspiration may decrease the pressure in the lungs
(intrapulmonary pressure) by only about 3mmHg. However, during maximal respiratory effort, such as
during exhaustive exercise, the intrapulmonary pressure may decrease by 80 – 100 mmHg.
Pulmonary Ventilation
Expiration
Expiration
nExpiration is…
uUsually a passive process.
uInvolves the relaxation of the inspiratory muscles and the recoil of the tissues.
nThe diaphragm relaxes.
nThe external intercostals relax.
nThe elastic nature of the lung tissue causes the lungs to recoil to its resting size.
Expiration
nAll this activity increases the pressure in the thorax.
uSo air is forced out.
uThus expiration is accomplished.
Expiration and Exercise
nDuring exercise expiration becomes a more active process.
uThe internal intercostals muscles can actively pull the ribs down.
uThis can be assisted by the latissimus dorsi and quadratus lumborum muscles.
tThis increases the pressure on the diaphragm, causing faster contraction, therefore accelerating return.
Review of Pulmonary Respiration
nPulmonary ventilation (breathing) is the process by which air is moved into and out of the lungs. It has
two phases: inspiration and expiration.
nInspiration is an active process through which the diaphragm and the external intercostal muscles
increase the dimensions, and thus the volume, of the thoracic cage. This decreases the pressure in the lungs
and draws air in.
Review of Pulmonary Respiration
nNormal expiration is a passive process. The inspiratory muscles relax and the elastic tissue of the lungs
recoil, retuning the thoracic cage to its smaller, normal dimensions. This increases the pressure in the
lungs and forces air out.
nForced or laboured inspiration and expiration are active processes, dependant on muscle action.
Pulmonary Diffusion
Gas Exchange in the Lungs
Pulmonary Diffusion
nAir was brought into the lungs during pulmonary ventilation;
tGas exchange must occur between this air and the blood.
nThis process is known as pulmonary diffusion.
Pulmonary Diffusion
nPulmonary diffusion is the process by which gases are exchanged across the respiratory membrane in
the alveoli.
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Functions of Pulmonary Diffusion
nIt replenishes the blood’s O2 supply.
nIt removes CO2 from returning venous blood.
The Process of Pulmonary Diffusion
nBlood from most of the body returns through the ______ (shown in red) to pulmonary (______)
The Venae Cava and Pulmonary Side of the Heart
The Process of Pulmonary Diffusion
nFrom the right ventricle, this blood is pumped through the pulmonary artery to the lungs, ultimately
working its way into the pulmonary capillaries.
nThese capillaries form a dense network around the alveolar sacs.
nThe vessels are small enough that the red blood cells can pass through but in single file.
The Respiratory Membrane
nGas exchange between the air and the alveoli and the blood in the pulmonary capillaries occurs across
the respiratory membrane.
The Respiratory Membrane
The Respiratory Membrane
nIs composed of.
tThe alveolar wall,
tThe capillary wall, and,
tTheir basement membranes.
nIt is very thin, measuring only 0.5 to 4.0 Цm.
nThis membrane presents a barrier for gas exchange.
nLets now look how this gas exchange occurs.
Partial Pressure
nThe air we breathe is a mixture of gases.
uEach exerts a pressure in proportion to its concentration in the gas mixture.
nThe individual pressures from each gas in a mixture is referred to as partial pressures.
nTherefore as according to Dalton’s law, the total pressure of a mixture of gases equals the sum of the
partial pressures of the individual gases in the mixture.
Key Point
nThe total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases in
that mixture.
The Air We Breathe
uThe air we breathe is composed of:
n79.04% Nitrogen (N2).
n20.93% Oxygen (O2).
n0.03% Carbon Dioxide (CO2).
The standard atmospheric pressure is approximately.
q760mmHg.
qThis is considered the total pressure of the three gases or 100%.
Partial Pressures of the Gases We Breathe
nNitrogen.
n% of air = 79.04%.
n79.04% of total atmospheric pressure.
n(0.7904 x 760mmHg).
n = 600.7mmHg.
nPN2 = 600.7mmHg.
Partial Pressures of the Gases We Breathe
nOxygen:
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n% of air = 20.93%.
n20.93% of total atmospheric pressure.
n(0.2093 x 760mmHg).
n= 159.0mmHg.
nPO
2=
159.0mmHg.
Partial Pressures of the Gases We Breathe
nCarbon Dioxide:
n% of air = 0.03%.
n0.03% of total atmospheric pressure.
n(0.003 x 760mmHg).
n= 0.3mmHg.
nPCO2 = 0.3mmHg.
Important Point
nGases in our bodies are dissolved in fluids, such as blood plasma.
nAccording to Henry’s law,
ugases dissolve in liquids in proportion to their partial pressures, depending also on their solubilities in the
specific fluids and on the temperature.
Important Point
nA gas’s solubility in blood is constant, and blood temperature is relatively constant.
nThus the most critical factor for gas exchange between the alveoli and blood is:
uThe pressure gradient between the gases in the two areas.
Gas Exchange in the Alveoli
nDifferences in the partial pressure of the gases in the alveoli and the gases in the blood create a pressure
gradient across the respiratory membrane.
nThis forms the basis of gases exchange during pulmonary diffusion.
nWhat would happen if the pressures were equal?
Key Point
nThe greater the pressure gradient across the respiratory membrane, the more rapidly oxygen will diffuse
across it.
Gas Exchange in the Alveoli
Oxygen Exchange
nPO2 = 159mmHg.
nThis drops to 100 –105mmHg when air is inhaled and enters the alveoli.
nThe blood, stripped of much of its O2 enters the pulmonary capillaries with a PO2 = 40 –45mmHg.
nThis is about 55 mmHg less than PO2 in the alveoli.
nIt is this pressure gradient that drives the O2 from the alveoli into the blood.
Oxygen Exchange
Oxygen Exchange
nThe rate in which O2 diffuses from the alveoli into the blood is referred to as the oxygen diffusion
capacity.
nAt rest approx 23 ml of O2 diffuses per minute.
nDuring maximal exercise this can raise to 45 ml in the untrained athlete and 80 ml in the trained athlete.
Training and O2 Diffusion Capacity
nAthletes with large aerobic capacities often also have greater oxygen diffusion capacities.
nThis is likely the combined result of:
uIncreased cardiac output.
uIncreased alveolar surface area, and,
uReduced resistance to diffusion across respiratory membranes.
Carbon Dioxide Exchange
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nCO 2 exchange, like O2 exchange, moves along a pressure gradient.
nBlood passing through the.
uAlveoli has PCO 2 of about 45mmHg.
uThe alveoli air has PCO2 = 40mmHg.
nThis results is a relatively small pressure gradient of about 5mmHg.
nIs this a problem? How do we over come this problem?
Pulmonary Diffusion Review
nPulmonary diffusion is the process by which gases are exchanged across the respiratory membrane in the
alveoli.
Pulmonary Diffusion Review
nThe amount of gas exchange that occurs across a membrane primarily depends on the partial pressure of
each gas, though gas solubility and temperature are also important. Gases diffuse along a pressure gradient,
moving from an area of higher pressure to one of lower pressure. Thus oxygen enters the blood and carbon
dioxide leaves it.
Pulmonary Diffusion Review
nOxygen diffusion capacity increases as you move from rest to exercise. When your body needs more
oxygen, oxygen exchange is facilitated.
nThe pressure gradient for carbon dioxide exchange is less than for oxygen exchange, but carbon dioxide’s
membrane solubility is 20 times greater than that of oxygen, so carbon dioxide crosses the membrane
easily, even without a large pressure gradient.
Transport of Oxygen and Carbon Dioxide
How Gases Are Transported
Transport of Oxygen and Carbon Dioxide
nNow we have considered how we bring air into our lungs via pulmonary ventilation and how gas
exchange occurs via pulmonary diffusion. Next we must consider how gases are transported in our blood
to deliver the oxygen to the tissues and to remove the carbon dioxide that the tissues produce. We will
consider separately the transport of each gas.
Oxygen Transport
nO2 is transported by the blood either,
u Combined with haemoglobin (Hb) in the red blood cells (>98%) or,
uDissolved in the blood plasma (<2%).
Oxygen Transport
nOnly about 3 ml of O2 are dissolved in each litre of plasma.
nAssuming we have a total plasma volume of 3 to 5 litres, only about 9 – 15 ml of O2 can be carried in the
dissolved state.
Oxygen Transport
nThis is not enough to supply even the resting body, which requires 250ml per minute.
nFortunately we have four to six billion haemoglobin containing red blood cells.
nThe haemoglobin allows nearly 70 times more O2 than dissolved in plasma.
Haemoglobin Saturation
nHaemoglobin saturation is the amount of oxygen bound by each molecule of haemoglobin
Haemoglobin Saturation
nEach molecule of haemoglobin can carry four molecules of O2.
nWhen oxygen binds to haemoglobin, it forms OXYHAEMOGLOBIN;
nHaemoglobin that is not bound to oxygen is referred to as DEOXYHAEMOGLOBIN.
nShow the haemoglobin.
Haemoglobin Saturation
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nThe binding of O2 to haemoglobin depends on the PO2 in the blood and the bonding strength, or affinity,
between haemoglobin and oxygen.
nThe graph on the following page shows an oxygen dissociation curve, which reveals the amount of
haemoglobin saturation at different PO 2 values.
Dissociation Curve
nReveals the amount of haemoglobin saturation at different PO values.
2
Haemoglobin Saturation
nA high blood PO2 results in almost complete haemoglobin saturation, which means the maximum amount
of oxygen is bound.
nBut as the PO2 is reduced, so is haemoglobin saturation.
Factors Affecting Haemoglobin Saturation
nBlood acidity…
nBlood temperature…
Factors Affecting Haemoglobin Saturation – Blood Acidity
nIf the blood becomes more acidic the dissociation curve shifts right.
nThis means that more oxygen is being uploaded from the haemoglobin at tissue level.
nSee overhead.
Factors Affecting Haemoglobin Saturation – Blood Acidity
nLook at the overhead.
nThe rightward shift of the curve is due to a decline in pH. This is referred to as the BOHR effect.
nSo why is this important to us?????
Factors Affecting Haemoglobin Saturation – Blood Acidity
nThe pH in the lungs is generally high.
tWhat does this mean?
nSo haemoglobin passing through the lungs has a strong affinity for oxygen, encouraging high saturation.
nAt the tissue level, however the pH is lower, causing oxygen to dissociate from haemoglobin, thereby
supplying oxygen to the tissues.
Factors Affecting Haemoglobin Saturation – Blood Acidity
nWith exercise, the ability to upload oxygen to the muscles increases as the muscle ph decreases.
Factors Affecting Haemoglobin Saturation – Blood Temperature
nLook at overhead.
nIncreased blood temperature shifts the dissociation curve to the right, indicating that oxygen is uploaded
more efficiently.
Factors Affecting Haemoglobin Saturation – Blood Temperature
nBecause of this, the haemoglobin will upload more oxygen when blood circulates through the
metabolically heated active muscles.
nIn the lungs, where the blood might be a bit cooler, haemoglobin’s affinity for oxygen is increased. This
encourages oxygen binding.
Key Point
nIncreased temperature and hydrogen ion (H+) (pH) concentration in exercising muscle affect the oxygen
dissociation curve, allowing more oxygen to be uploaded to supply the active muscles.
Carbon Dioxide Transport
nCarbon dioxide also relies on the blood fro transportation. Once carbon dioxide is released from the
cells, it is carried in the blood primarily in three ways…
nDissolved in plasma,
nAs bicarbonate ions resulting from the dissociation of carbonic acid,
nBound to haemoglobin.
Dissolved Carbon Dioxide
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nPart of the carbon dioxide released from the tissues is dissolved in plasma. But only a small amount,
typically just 7 – 10%, is transported this way.
nThis dissolved carbon dioxide comes out of solution where the PCO2 is low, such as in the lungs.
nThere it diffuses out of the capillaries into the alveoli to be exhaled.
Bicarbonate Ions
nThe majority of carbon dioxide ions is carried in the form of bicarbonate ion.
n60 - 70% of all carbon dioxide in the blood.
nThe following bit is quite heavy just listen hard.
Bicarbonate Ions
nCarbon Dioxide and water molecules combine to form carbonic acid (H2CO3).
nThis acid is unstable and quickly dissociates, freeing a hydrogen ion (H+) and forming a bicarbonate ion
(HCO3-):
nCO2 + H2O
H2CO3
CO 2 + H2O
Bicarbonate Ions
nThe H+ subsequently binds to haemoglobin and this binding triggers the BOHR effect (mentioned
earlier).
nThis shifts the oxygen-haemoglobin dissociation curve to the right.
nThus formation of bicarbonate ion enhances oxygen uploading.
Bicarbonate Ions
nThis also plays a buffering as the H+ is neutralised therefore preventing any acidification of the blood.
nWhen blood enters the lungs, where the PCO2 is lower, the H+ and bicarbonate ions rejoin to form
carbonic acid, which then splits into carbon dioxide and water.
nIn other words the carbon dioxide is re-formed and can enter the alveoli and then be exhaled.
Key Point
nThe majority of carbon dioxide produced by the active muscles is transported back to the lungs in the
form of bicarbonate ions.
Carbaminohaemoglobin
nCO2 transport also can occur when the gas binds with haemoglobin, forming a compound called
Carbaminohaemoglobin.
nIt is named so because CO2binds with the amino acids in the globin part of the haemoglobin, rather than
the haeme group oxygen does.
In Review
nOxygen is transported in the blood primarily bound to haemoglobin though a small amount is dissolved
in blood plasma.
nHaemoglobin oxygen saturation decreases.
nWhen PO2 decreases.
nWhen pH decreases.
nWhen temperature increases.
In Review
Each of these conditions can reflect increased local oxygen demand. They increase oxygen
uploading in the needy area.
3) Haemoglobin is usually about 98% saturated with oxygen. This reflects a much higher oxygen content
than our body requires, so the blood’s oxygen-carrying capacity seldom limits performance.
In Review
4) Carbon dioxide is transported in the blood primarily as bicarbonate ion. This prevents the formation of
carbonic acid, which can cause H+ to accumulate, decreasing the pH. Smaller amounts of carbon dioxide
are carried either dissolved in the plasma or bound to haemoglobin
Gas Exchange at the Muscles
Gas Exchange at the Muscles
nNow we have considered how our respiratory and cardio-vascular system brings air into our lungs,
exchange oxygen and carbon dioxide in the alveoli, and transport oxygen to the muscles (and CO2 away
from them).
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nAll that remains is for us to consider the delivery of oxygen to the muscles from the capillary blood.
nThis gas exchange between the tissue and the blood in the capillaries is our fourth and final step in gas
transportation – internal respiration.
The Arterial-venous Oxygen Difference
nAt rest, the oxygen content of arterial blood is about 20ml of oxygen per 100 ml of blood.
nSee over head.
nThe value drops to 15 or 16ml of oxygen per 100ml as the blood passes through the capillaries into the
venous system.
nThis difference in oxygen content between arterial and venous blood is referred to as the arterial-venous
oxygen difference (a-VO2diff).
The Arterial-venous Oxygen Difference
nIt reflects the 4-5 ml of oxygen per 100 ml of blood taken up by the tissues.
nThe amount of oxygen taken up is proportional to its use for oxidative energy production. Thus as the
rate of oxygen use increases, the a-vO2 diff also increases.
The Arterial-venous Oxygen Difference
nE.g. during intense exercise (figure see OHP) the a-vO2 diff in contracting muscles can increase to 15 to
16 ml per 100ml of blood. During such an effort, the blood unloads more oxygen to the active muscles
because the PO2 in the muscles is drastically lower than in arterial blood.
Key Point
nThe a-vO2 diff increases from a resting value of about 4 to 5 ml per 100 ml of blood up to values of 15 to
16 ml per 100 ml of blood during exercise. This increase reflects an increase extraction of oxygen from
arterial blood by active muscle, thus decreasing the oxygen content of the venous blood.
Factors Influencing Oxygen Delivery and Uptake.
nThe rates of oxygen delivery and uptake depend on the three major variables.
tThe oxygen content of blood.
tThe amount of blood flow.
tThe local conditions.
nAs we begin to exercise, each of these variables must be adjusted to ensure increased oxygen delivery to
our active muscles.
Factors Influencing Oxygen Delivery and Uptake.
nWe have discussed in class that under normal circumstances haemoglobin is 98% saturated with oxygen.
nAny reduction in the blood’s normal oxygen carrying capacity would hinder oxygen delivery and reduce
cellular uptake of oxygen.
Factors Influencing Oxygen Delivery and Uptake.
nExercise causes increased blood flow through the muscles. As more blood carries oxygen through the
muscles, less oxygen must be removed from each 100 ml of blood (assuming the demand remains
unchanged).
nThus increasing blood flow improves oxygen delivery and uptake.
Factors Influencing Oxygen Delivery and Uptake.
nMany local changes in the muscle during exercise affect oxygen delivery and uptake.
nMuscle activity increases muscle acidity because of lactate production.
nMuscle temperature and carbon dioxide concentration both increase because of increased metabolism.
nAll of these increase oxygen uploading from haemoglobin molecule, facilitating oxygen delivery and
uptake by the muscles.
Factors Influencing Oxygen Delivery and Uptake.
nDuring maximal exercise,however, when we push our bodies to the limit, changes in any of these areas
can impair oxygen delivery and restrict out abilities to meet oxidative demands.
Carbon Dioxide Removal
nCarbon dioxide exits the cells by simple diffusion in response to the partial pressure gradient between the
tissue and the capillary blood.
nE.g. Muscles generate carbon dioxide through oxidative metabolism, so the PCO2 in muscles would be
relatively high compared to that in the capillary blood. Consequently, CO2 diffuses out of the muscles and
into the blood to be transported to the lungs.
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AS Level Sport and Physical Education Class
Home Work – Please answer the following questions on a piece of paper
and hand it to me either before or in Thursday’s lesson
Respiration and The Respiratory System
1) Explain in detail external respiration – include both the inspiration (including the passage of
oxygen along the respiratory passageways) and expiration. It would be advantageous to include
information on partial pressure plus other relevant information. (15 marks)
2) Explain in detail gaseous exchange at the lungs – include the pressure gradient, respiratory
membrane, and diffusion plus any other relevant information.
(15 marks)
NB - Please note the topics I have highlighted in these questions will not give a definitive answer.
For full marks I will need to see more detail.
3) What substances carries oxygen in the blood?
(1 mark)
4) Why is carbon monoxide so dangerous to the respiratory system?
Clue - think about oxygen and the substance named above.
(2 marks)
5) What is tidal volume?
(1 mark)
6) What is the inspiratory reserve volume?
(1 mark)
7) Identify the muscles used in respiration at rest and during exercise.
(4 marks)
8) Identify and explain four factors that influence the efficiency of gaseous exchange between the
lungs and the pulmonary capillaries.
(4 marks)
Clue – the answer can be found in the respiratory chapter in your textbook.
AS Level Sport and Physical Education
Homework of 30th October
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Hand in Thursday 7h November
Name_____________________
Answer all the questions on the sheet.
2
3
4
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5
6
7
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Name_____________________
Answer all the questions on the sheet.
2
3
4
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5
6
7
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The breathing characteristics of games players may alter during performance. Figure 3
shows the proportion of oxygen and carbon dioxide breathed during exercise compared with
rest.
Figure 3
(i) Use the information in Figure 3 to describe the effects of exercise on gas exchange in
the lungs. Suggest why these changes occur. (3 marks)
(ii) In what form are carbon dioxide and oxygen transported by the blood? (2 marks)
(iii) Explain the causes of the increase in breathing rate experienced during exercise.
(3 marks)
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