This document discusses the structures and functions of the respiratory system. It begins by listing the principal structures of the ventilatory system, including the nose, mouth, pharynx, larynx, trachea, bronchi, bronchioles, lungs and alveoli. It then discusses the role of smooth muscle tissue and describes the trachea in more detail. Subsequent sections outline the functions of the conducting airways, define various respiratory terms, explain the mechanics of ventilation in the lungs involving changes in pressure, and describe the significance of carbon dioxide and role of hemoglobin in oxygen transportation and the process of gaseous exchange at the alveoli.

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Exercise physiology
2.1.1 List the principal structures of the
ventilatory system
Topic 2
Exercise
Physiology
 The principle structures of the respiratory system are:
 Nose/Mouth
 Pharynx
 Larynx: voice box
 Trachea
 Bronchi
 Bronchioles
 Lungs
 Alveoli
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.1 List the principal structures of the
ventilatory system
Topic 2
Exercise
Physiology
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system
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2.1.1 List the principal structures of the
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Physiology
 Smooth muscle tissue is found on the walls of some of our internal hollow organs It produces smooth, rhythmical actions.
 We can not consciously control the action of smooth muscle. It is subsequently termed involuntary.
e.g. movement of blood and air in the lungs
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1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.1 List the principal structures of the
ventilatory system
Topic 2
Exercise
Physiology
 The trachea is a thin walled tube about the diameter of an average garden hose. It is composed of very thin, tough connective
tissue and is strengthened at intervals by incomplete rings of cartilage.
 The trachea muscle runs down the posterior wall of the trachea. This is an example of smooth muscle.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.2 Outline the functions of the conducting
airways
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Exercise
Physiology
 The nostrils are fringed with coarse hair, which strains large particles out of the airstream and may also serve to protect the nasal cavity from invasion by insects.
 The interior of the nasal cavity contains projections of considerable surface area. These projections, nasal conchae, make the airstream turbulent and subsequently warm and hydrate it.
 Thanks to the structure of the nose, air entering the trachea is virtually 100% humidified.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.2 Outline the functions of the conducting
airways
Topic 2
Exercise
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1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.2 Outline the functions of the conducting
airways
Topic 2
Exercise
Physiology
 Air passes through the 3 portions of the pharynx, which provides a low resistance path for airflow, to the trachea via the larynx.
 In addition to it’s function as the voice box the larynx protects the trachea from invasion by foods and fluids.
 The cartilaginous trachea, branches into the two main bronchi.
 The lining of the tracheobronchial system is designed to protect the lungs from dehydration and invasion by foreign particles, including micro-organisms.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.2 Outline the functions of the conducting
airways
Topic 2
Exercise
Physiology
 The lungs themselves develop at the end of the bronchi. They are elastic spongy organs.
 Gas exchange is carried out by a complex of structures at the end of each terminal bronchioles.
They are simple thin walled structures which also have numerous thin-walled outpocketings called alveoli, which are specialised for the function of gaseous exchange.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.3 Define respiratory terms
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Physiology
 Pulmonary ventilation: is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration
(exhalation). Air flows because of pressure differences between the atmosphere and gases inside the lungs.
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1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.3 Define respiratory termsTopic 2
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Physiology
 Air, like other gases, flows from a region with higher pressure to a region with lower pressure. Muscular breathing movements and recoil of
elastic tissues create the changes in pressure that result in ventilation. Pulmonary ventilation involves three different pressures:
• Atmospheric pressure
• Intraalveolar (intrapulmonary) pressure
• Intrapleural pressure
Atmospheric pressure is the pressure of the air outside the body. Intraalveolar pressure is the pressure inside the alveoli of the lungs.
Intrapleural pressure is the pressure within the pleural cavity. These three pressures are responsible for pulmonary ventilation.
http://training.seer.cancer.gov/module_anatomy/unit9_2_resp_vent_mechanics.html1. Structure &
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2. Structure &
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cardiovascular
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2.1.3 Define respiratory termsTopic 2
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Physiology
It is important to understand the various volumes and capacities of the lungs in order to appreciate the
effects of exercise on the respiratory system.
 Total lung capacity can be calculated by adding vital capacity to residual volume of the lungs.
 During normal, quiet respiration, about 500mL of air is inspired. The same amount of air moves out
with expiration. This volume of air is called the tidal volume.
 When we forcibly take a deep breath, we can take in up to 3100mL above the tidal volume. This
additional air is the inspiratory reserve volume.
 Browne et. al 2001
1. Structure &
function of the
ventilatory
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2. Structure &
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2.1.3 Define respiratory termsTopic 2
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 We can also forcibly exhale. This is termed the
expiratory reserve volume.
 Even after the expiratory reserve volume is expelled,
some air is still trapped in the lungs because of
pressure. This is called the residual volume.
 Browne et al 2001
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1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
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2.1.4 Explain the mechanics of ventilation in
the human lungs
Topic 2
Exercise
Physiology
To understand how a person breathes, you need to know that a substance
called pleural fluid lies between the lungs and the chest wall.
Have you ever put two pieces of wet glass together (e.g. microscope slides) and
found that you could not easily pull them apart. This phenomenon results from a
combination of forces – surface tension, molecular cohesion and atmospheric
pressure.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
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2.1.4 Explain the mechanics of ventilation in
the human lungs
Topic 2
Exercise
Physiology
Think of the walls of the chest and the lungs as the two wet slides and the pleural fluid
as the film of water. When the chest expands during breathing, the film of pleural fluid
causes the membranous walls of the lungs to be pulled outward along with the chest
walls. This means the space within the lungs increases. The air molecules in the lungs
now move momentarily farther apart, so that the pressure in of the air in the lungs falls
below the pressure of the atmosphere outside the body.
Consequently, air from outside rushes down the trachea and into the lungs until the
two pressures are equal again. This is the process of inspiration.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.4 Explain the mechanics of ventilation in
the human lungs
Topic 2
Exercise
Physiology
Observation of the skeleton reveals that each rib pivots about a
vertebral joint. If it is lifted upward it also swings outward, with the
thoracic cavity being enlarged anteriorly and superiorly. This is the task
in quiet breathing of the external intercostal muscles.
At the same time the ribs are lifted, the diaphragm (the muscular floor
of the thoracic cavity) contracts downward enlarging the thoracic cavity
inferiorly. This process enlarges the cavity twofold.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.4 Explain the mechanics of ventilation in
the human lungs
Topic 2
Exercise
Physiology
Expiration is almost entirely a passive process that depends on
the elasticity of the lungs and chest structures, as well as fluid
film surface tensions within the lungs. When inspiratory muscles
are relaxed, air simply leaves the lung, much as it would leave
an untied balloon.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.4 Explain the mechanics of ventilation in
the human lungs
Topic 2
Exercise
Physiology
 This above description is for quiet breathing. When one speaks or runs, the abdominal
muscles press upon the abdominal contents, squeezing them upwards against the
diaphragm. The internal intercostal muscles oppose the external intercostals and pull the
ribcage downward, helping to decrease the thoracic cavity volume and forcibly empty the
lungs. The diaphragm may also function in forcible expiration.
 In laboured inspiration (e.g. accompanying exercise) many of the muscles of the upper
trunk are also recruited. They are only indirectly attached to the ribs and are inefficient as
respiratory muscles. E.g. Pectoralis major and minor, Trapezius, Rhomboideus.
Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.4 Explain the mechanics of ventilation in
the human lungs
Topic 2
Exercise
Physiology
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1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.5 Describe the significance of carbon
dioxide in the control of pulmonary ventilation
Topic 2
Exercise
Physiology
 The entire respiratory system would be useless unless the alveolar air were regularly
changed. Since humans do not possess a one-way system for air circulation through
the lungs, inhaled an exhaled air must be mixed to some degree. This does not
normally produce any difficulty, since the respiratory system possesses a two to
threefold margin of safety and is ordinarily far more effective than it needs to be in
regard to oxygen absorption.
 Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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2.1.5 Describe the significance of carbon
dioxide in the control of pulmonary ventilation
Topic 2
Exercise
Physiology
 This is less true, however for carbon dioxide removal, which is an
equally important task of the respiratory system. Fortunately, carbon
dioxide diffuses through the alveolar walls far more readily than
oxygen, but dissolved carbonic acid does not readily breakdown to
form carbon dioxide. Were it not for the enzyme carbonic anhydrase,
which speeds the dissociation of carbonic acid as well as it’s
formation, the elimination of this gas would be hopelessly inadequate.
 As it is, carbon dioxide excretion is far more easily hindered than is
oxygen absorption. Thus breathing is governed not by oxygen, but the
carbon dioxide content of the blood.
 Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

21. IB
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Exercise physiology
2.1.5 Describe the significance of carbon
dioxide in the control of pulmonary ventilation
Topic 2
Exercise
Physiology
 Whilst respiration appears at first a voluntary activity, if that were true it would not
continue when were asleep or inattentive. It is subject to great conscious influence, but
despite the fact it is carried out by such voluntary muscles as the intercostals and the
diaphragm, breathing is basically an automatic and involuntary activity.
 Solomon & Davis
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

22. IB
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Exercise physiology
2.1.6 Outline the role of hemoglobin in oxygen
transportation
Topic 2
Exercise
Physiology
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/19510.jpg

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2.1.6 Outline the role of hemoglobin in oxygen
transportation
Topic 2
Exercise
Physiology
Hemoglobin is the iron containing oxygen transport protein in the red blood cells. It transports
oxygen from the lungs to the rest of the body, such as the muscles, where it releases it’s load
of oxygen.
The name hemoglobin is the concatenation of heme and globin, reflecting the fact that each
subunit of hemoglobin is a globular protein with an embedded heme (or haem) group; each
heme group contains an iron atom, and this is responsible for the binding of oxygen. In
humans, each heme group is able to bind one oxygen molecule with one hemoglobin molecule
can therefore bind four oxygen molecules.
http://en.wikipedia.org/wiki/Hemoglobin
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

24. IB
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Exercise physiology
2.1.7 Explain the process of gaseous
exchange at the alveoli
Topic 2
Exercise
Physiology
 Gas exchanges between the air in the alveoli and the blood capillaries occur
across the respiratory membrane in a process known as pulmonary
diffusion. The most critical factor for gas exchange between alveoli and the
blood is the pressure gradient between the gases in the two areas.
 According to Dalton’s law of partial pressures, the pressure of a mixture of
gases equals the sum of the individual pressures (partial pressures) of each
gas in the mixture.
Browne et.al
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

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Exercise physiology
2.1.7 Explain the process of gaseous
exchange at the alveoli
Topic 2
Exercise
Physiology
 If we take a normal breath of air, which contains nitrogen, oxygen and
carbon dioxide, the total pressure of the air is equal to the sum of the partial
pressures of the individual gases in the blood and the alveoli create a
pressure gradient, so one into the other (from high partial pressure to low
partial pressure)
 The partial pressure of oxygen arriving at the alveoli is high, and the
partial pressure of it in the capillaries is low. Therefore oxygen diffuses from
the alveoli into the blood. The opposite is true for carbon dioxide.
Browne et.al
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

26. IB
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Exercise physiology
2.1.7 Explain the process of gaseous
exchange at the alveoli
Topic 2
Exercise
Physiology
1. Structure &
function of the
ventilatory
system
2. Structure &
function of the
cardiovascular
system

27. Be prepared for discussions
• Affect of exercise on hemoglobin at altitude
• What are some of the effects/results of
breathing air at altitude? Below sea level?
• What is the theory behind hyperventilation
for improved breath holding ability?