Basic Anatomy andBasic Anatomy and
Respiratory SystemRespiratory System
Cells continuously use O2 in the metabolic
reactions in the body to create energy. At the
same time, these reactions produce CO2.
The cardiorespiratory system O2 provides and
eliminates CO2 and other wastes through the blood
in a process known as respiration.
The bloodstream delivers chemical fuels to the
cell. Fuels are broken down in the cell to release
energy and this is called cellular respiration.
As CO2 in the cell accumulates, the concentration is
higher than that in the bloodstream. The
CO2 diffuses to the bloodstream.
As O2 concentration is higher in the bloodstream, O2
diffuses to the cells.
How does the circulatory system release CO2 from
the body into the atmosphere?
How does O2 get into the blood?
This occurs in the lungs.
Glucose + O2 → CO2 + H2O + Energy
STRUCTURES OF THE RESPIRATORY SYSTEM
UPPER RESPIRATORY TRACT
1. NASAL PASSAGES
Air enters through nostrils
Small hairs filter out dust and large particles
Air passes through to the nasal passageways
Mucus layer traps finer particles, which are carried by cilia to the
pharynx (throat) to be swallowed
Passageway for air and food and to provide a resonating chamber
for speech sounds
4. OROPHARYNX and LARYNGOPHARYNX
Oropharynx connects nasopharynx to laryngopharynx
Laryngopharynx extends to the oesophagus and larynx
Contains the vocal cords and connects the pharynx with the
Thyroid cartilage (Adam’s Apple) gives its triangular shape
Epiglottis is a large leaf shaped piece of cartilage lying on
the top of the larynx. It forms a lid over the trachea to
prevent foreign bodies and liquid going down.
LOWER RESPIRATORY TRACT
C-shaped cartilage rings reinforce and protect the
trachea to prevent it from collapsing
Conducts air through to bronchi
Right and left primary bronchi are formed
from the branching of the trachea
Inside each lung, the primary bronchus
branches into secondary and then tertiary
The process continues until the tiniest
branches of the whole system are the air
passages called the bronchioles (less than 1
mm in diameter)
Known as bronchial tree
Paired organs lying in the thoracic cavity that sit either side
of the heart
Each is surrounded by a strong connective tissue called the
pleura membrane. This contains two layers: the parietal
pleura, which are attached to the thoracic cavity, and the
visceral pleura that cover the lungs. Between them is the
pleural cavity, which contains lubricating fluid to prevent
friction between the membranes when breathing
Each lung is divided by fissures into lobes. The left lung has
2 lobes; the right lung has 3
The left lung has a ‘cardiac notch’ to accommodate the shape
of the heart
At the end of the bronchioles are small sacs called alveoli
The total surface area of the alveoli amounts to about 1
square meter per kilogram of body weight. Therefore, a
person who is around 65kg would have 65m² of alveoli surface
area (nearly half a tennis court)
Alveoli are covered in tiny capillaries
Exchange of gases occurs between the alveolar and capillary
walls across a thin membrane. This is called diffusion.
Respiration is the exchange of gases between the cells, blood
It involves four processes
1. Pulmonary Ventilation (breathing) – the movement of air
from the atmosphere into the alveoli
2. Pulmonary Diffusion – exchange of O2 and CO2 between the
lungs and the blood
3. Transport of Respiration Gases – transportation of O2 and
CO2 between the lungs and the tissue cells of the body via
4. Internal Respiration – gas exchange between the blood
capillaries and the tissue cells.
INSPIRATION AND EXPIRATION
Pulmonary ventilation (breathing) allows a continuous flow
of air from the outside into and out of the lung alveoli
Air flows in to the body and out of it for the same reason
that blood flows through the body – a pressure gradient
Gases will generally move from areas of high pressure
into areas of low pressure
Breathing in (inspiration) occurs because the air outside
has a higher pressure than the air in the lungs as your
muscles have increased the size and the volume inside the
When the diaphragm and external intercostals relax, the
pressure inside the lungs is greater than that outside as
the lung size and volume has decreased. Hence we breathe
out in the process of expiration.
OVERVIEW OF THE MECHANICS OF BREATHING
The diaphragm muscle contracts and flattens
The intercostals raise the thorax and the sternum out
The chest cavity is enlarged and pressure is reduced
Air is drawn in
The diaphragm relaxes and
forms a dome shape
The chest cavity is reduced
The pressure is increased
Air is forced out
CONTROL OF BREATHING
The basic pattern of breathing is set by the activity of
neurons in the Medulla and Pons (base of the brain)
This centre in the brain senses the level of CO2 in the blood
and signals the body to breathe out (to get rid of CO2) and to
breathe in as O2 is needed
Neurons fire, nerve impulses travel along the intercostal
nerves to excite the diaphragm and external intercostal
The thorax expands and air rushes into the lungs
The inspiration centre becomes dormant and the muscles
recoil allowing expiration
Rate = 12 – 18 breaths / min
Inspiratory Phase is approximately 2 seconds
Expiratory Phase is approximately 3 seconds
During normal, quiet respiration, about 500mL of air is
inspired (350 mL reaches the alveoli; the other 150 mL remains
in the respiratory space). The same amount of air moves out
with expiration. This volume of air is called the Tidal Volume.
The total amount of air breathed in over one minute is about 6
litres, and is called the Minute Volume of Respiration
(ventilation). Tidal volume x Number of breaths per minute
(0.5L x 12 breaths / min = 6L/min)
We can forcibly take in a deep breathe, we can take in up to
3100 mL above the tidal volume. This additional air is the
Inspiratory Reserve Volume
We can forcibly breathe out (exhale). This is termed the
Expiratory Reserve Volume, and can amount up to 1200 mL
more than the tidal volume.
Even after the expiratory reserve volume is expelled, some air
is still trapped in the lungs because of pressure. This is the
Residual Volume, and it is usually around 1200 mL.
The lung capacities are various combinations of the
Tidal Volume + Inspiration Reserve Volume =
Inspiratory Capacity (3600 Ml)
Residual Volume + Expiratory Reserve Volume =
Functional Residual Capacity (2400 mL)
Tidal Volume + Inspiratory Reserve Volume +
Expiratory Reserve Volume = Vital Capacity (4800
To find the Total Lung Capacity, add all volumes =
The apparatus commonly used to measure the volumes of air
exchanged and the rate of ventilation is called a spirometer
The record of these readings is called a spirogram.
Inspiration is the upward deflection and expiration is the
Tidal volume (TV) increases
Inspiratory Reserve volume (IRV) decrease
Expiratory Reserve volume (ERV) slightly decreases
Residual volume (RV) slightly increases
Total lung capacity (TLC) slightly decreases
Vital capacity (VC) slightly decrease
When at rest, a total of 6 litres of blood passes through your lungs
every minute. This figure increases enormously during exercise.
(Davis et al, p.67, 1986)
IMMEDIATE RESPONSES TO EXERCISE
Before exercise, rate and depth of breathing increases as
nervous activity is increased.
Once exercising, rate and depth increase greatly because
increased amounts of CO2 in the blood trigger greater
The increase in frequency (rate) and depth (TV) provides
greater ventilation and occurs in proportion to the exercise
Lung volumes also change:
Increased TV – up to 5 or 6 times
EVR and IRV utilised more, thus decrease in volume
Blood flow is greater, therefore there are more open
capillaries at the alveolar-capillary membrane, increasing the
surface area in the lungs for gaseous exchange
When exercise ceases, the body returns to pre-exercise
condition or recovery period.
CO2 is reduced
Stimulation from muscles and joints is reduced
RESPIRATORY ADAPTATIONS TO EXERCISE
1. EFFECTS ON VENTILATION
Ventilation increases from 6L/min at rest to more than 100L/min
during exercise. This is achieved by increases in:
Respiration rate – from 15 to 40 or more breaths/min
Tidal Volume – from 10% of vital capacity to more than 50%
2. EFFECTS ON LUNG DIFFUSION
During strenuous exercise there is a threefold increase in oxygen
diffusion from the alveoli to the blood
3. EFFECTS ON OXYGEN UPTAKE (VO2)
Oxygen uptake is the amount of oxygen taken up and used by the
body. It reflects the total amount of work being done by the
During strenuous exercise there can be a 20-fold increase
in VO2, which increases linearly with the increase of
exercise intensities. As a person approaches exhaustion,
their VO2 will reach a maximum that will not go any
higher. This is a person’s VO2 max, the largest amount of
oxygen that a person can utilise within a given time.
LONG TERM RESPONSES TO EXERCISE
Regular exercise causes adjustments to the respiratory system
ie adaptation and benefit = improved lung function
The muscles involved in breathing are conditioned and
strengthened and the chest therefore has a greater ability to
Trained athletes have improved lung volume and lung function
and can therefore take in more air per breath, require less
breathing work to maintain same levels of O2 in the blood and can
utilise air more efficiently.
Increased lung volume results in improved diffusion of O2 from
lungs to the blood.
Lung volume at rest also becomes greater
These adjustments increase efficiency of gaseous
exchange and thus improve the amount of O2 to be
transported to body cells.
OXYGEN DEBT AND DEFICIT
These terms refer to a lack of oxygen while training/racing and after such
activity is over. To go into these areas of exercise are normal, but the
goal is to not go too far into either category. Below is a brief description
of each and a chart which will detail the process more clearly than we can
explain with words alone.
Oxygen Deficit – while exercising intensely the body is sometimes unable
to fulfil all of its energy needs. Specifically, it is unable to intake and
absorbs enough oxygen to adequately ‘fee’ the muscles and amounts of
energy needed to perform the tasks the athlete is requesting from the
body. In order to make up the difference without sacrificing the output,
the body must tap into its anaerobic metabolism. This is where the body
goes into a mix of aerobic and anaerobic energy production. While not
hugely detrimental, oxygen deficit can grow to a level that the anaerobic
energy system cannot cover. This can cause performance to deteriorate.
Oxygen Debt – this term describes how the body pays back its debt
incurred above after the exercise is over. You will notice that even after
you have finished racing, you will continue to breathe hard. At this point
your body is still trying to repay the oxygen debt that was created when
you were working hard. Technically, it is excessive
post-exercise oxygen consumption.
Check out the illustration below for a graphical
description of these terms.
The vital capacity of the lungs can be reduced by 10 –
15% after once cigarette.
Narrowing of the airways increases the mucus
Prolonged smoking results in tar and irritants coating
the lungs and reducing the elasticity of the alveoli. This
increases the resistance to airflow and decreases the
oxygen transporting capacity of the blood.
More oxygen is used for breathing when you are a
smoker. As a result there is less available to the working
muscles, which leads to fatigue at a faster rate.
Asthma is the result of an allergic reaction to pollen,
dust mite, and animals and/or cold, exercise, fumes,
smog, viral infection and anxiety.
Small muscles surrounding the bronchi
constrict and there is an over secretion of
mucus. The walls of the bronchi can swell
and narrow the airways causing coughing,
wheezing and shortness of breath.
Bronchitis is caused by bacterial infections, pollution and smoking.
The symptoms include increased mucus, coughing, wheezing and
Treatment is by antibiotics (usually penicillin)
Emphysema is caused by smoking and prolonged exposure to pollution
(eg coal miners)
The lining of the airways is damaged (cilia) and cannot move dirt and
mucus. This then accumulates and the alveoli become less elastic.
Oxygen uptake is then decreased and breathing (expiration) becomes
Pulmonary fibrosis is an abnormal formation of fibre-like scar
tissue in the alveoli (air sacs which take oxygen to the lungs
and expel carbon dioxide) and interstitial tissue (the tissues
between and surrounding the alveoli) of the lungs. It is a
chronic lung disease associated with inflammation.
Pulmonary Fibrosis Cont.
• Breathlessness, especially during exercise
• Chronic dry cough
• Shortness of breath
• Chest discomfort
• Reduced VC and IRV
• Exposure to cigarette smoke
• Inhaled environmental pollutants
• Occupational pollutants, including asbestos, ground stone, metal
dust or mouldy hay
Exercise at Altitude
Exercise at altitude can have a major effect on performance
Endurance performance is usually diminished and anaerobic
performance unaffected. This is because ascent to altitude results in
lower oxygen in inspired air, and therefore less oxygen delivery to
The percentage of oxygen in the air is at the same at sea level, but
the total amount of air is less.
A moderate altitude around 15oom can start to affect the athlete,
and over 5000m can be extreme.
An increase of altitude results in a decrease of 2°C per 300m, so
the cold also has to be dealt with.
Physiological responses to exercise:
Decreased arterial oxygen content
Increased CO2 output
Increased stroke volume
Decreased sub-max HR
Decreased VO2 max
Progressive dehydration – increased breathing of colder / dryer air
and increased urine.
Overcoming the Effects of Altitude
Live high / train low – maximise the resting adaptations to altitude
and minimise the disruption to training caused by altitude
Daily transit – between high and low altitude
Nitrogen houses – decreases O2 in the air by increasing nitrogen.
Mimic high altitude conditions and you can set the height you require
Altitude tents – portable and have a decreased O2.
Acclimatisation at Altitude
Adaptations occur over 2 – 3 weeks:
Increased red blood cell concentration – over days due to dehydration
and weeks / months due to increased cell production
Partial restoration of plasma volume
Increased muscle capillarisation
Increased muscle enzyme activity
This generally occurs above 3000m and is most likely to happen in:
After rapid ascent
In combination with exercise
Sleep disturbances due to cardiovascular responses to
* Pulmonary / cerebral edema may occur in extreme
circumstances and requires immediate return to lower