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Pulmonary Tuberculosis
Video
- Course of infection
- Symptoms
- Transmission
What is the cause of
pulmonary TB?
• Tuberculosis is caused
by one of two rodshaped bacteria.
• Either Mycobacterium
tuberculosis (pictured)
or Mycobacterium bovis.
What is the cause of
pulmonary TB?
• It is estimated that
around 30% of the
world’s population have
one or other form of the
bacterium within their
bodies.
What are the symptoms of
pulmonary TB?
• Persistent cough
• Tiredness
• Loss of appetite (leading to
weight loss)
As the disease develops:
• Fever
• Coughing up blood
Tuberculosis infection
When a person becomes infected with TB, an immune
response is produced.
In healthy people, white blood
cells called macrophages
engulf the bacteria by
phagocytosis, controlling the
infection.
A tissue mass called a tubercle
forms around the infected site,
and after 3–8 weeks the
infected region heals.
However, the bacteria can survive inside macrophages
for years until the immune system becomes weak.
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Symptoms of tuberculosis
If the patient’s immune system is unable to contain the
infection, active tuberculosis may occur. The bacteria will
multiply rapidly, destroying the lung tissue, which can be fatal.
A patient with active tuberculosis may experience symptoms
such as coughing, shortness of breath, loss of appetite,
weight loss, fever, night sweats and extreme fatigue.
Fever and night sweats occur due to neutrophils and
macrophages releasing fever-causing substances, as part of
the inflammatory response. These chemicals affect the
hypothalamus and increase core body temperature.
Why might an increase in temperature be harmful?
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Course of Infection
infection – enlargement of lymph
nodes that drain the area of the lungs, due
to accumulation of white blood cells at the
site of infection.
 Post-primary infection – the dormant
bacteria re-emerge many years later to
cause an infection in the upper regions of
the lungs.
 The bacteria destroy the lung tissue.
 Primary
TB and HIV
Try the questions.
http://www.youtube.com/watch?v=Gh
2Ovh0uAss
Pulmonary fibrosis
Recap from last lesson....
1.
2.
3.
4.
5.
What is pulmonary tuberculosis?
What is it caused by?
How is it transmitted?
How does it affect the lungs?
How could it be prevented?
Lung disease
– fibrosis, asthma and emphysema
• Pulmonary tuberculosis is only one disease
which affects the lungs.
• Fibrosis, asthma and emphysema can all also
impair lung function in a number of different
ways...
Pulmonary Fibrosis
Description
Happens when scars form on the pulmonary epithelium, causing
them to become irreversibly thickened. This means that in patients
with fibrosis, O2 cannot diffuse properly into the blood. Fibrosis also
reduces the elasticity of the lungs and therefore makes ventilating
the lungs difficult.
Cause
The exact cause is unclear, but evidence suggests it is a reaction to
microscopic lung injury, to which some individuals are more
susceptible.
Cigarette smoking can increase the risk or worsen the disease.
Pulmonary Fibrosis
Symptoms
Shortness of breath, especially when exercising due to a decrease
in volume of lungs as there is an increase in scar (fibrous
connective) tissue. Thickened epithelium means that diffusion
pathway is greater. Loss of elasticity makes ventilation difficult. All of
these factors combine to decrease the rate of diffusion.
Chronic, dry cough due to the fibrous tissue causing an obstruction.
This is the body’s reflex to remove an obstruction.
Pain and discomfort in the chest occurs due to the pressure in the
lungs and hence damage from the mass of fibrous tissue.
Weakness and fatigue results from reduced intake of O2.
Pulmonary Fibrosis
Asthma
Description
Asthma is an example of a localised allergic reaction. It affects up to
10% of the world population and accounts of 2000 deaths each
year in the UK. Some of the most common allergens include pollen,
animal dander, faces of house dust mites.
It can be triggered or worsened by pollutants (e.g sulphur dioxide,
ozone, nitrogen oxides), exercise, cold air, anxiety or stress. These
allergens cause white blood cells to release histamines in the
bronchi and bronchioles, causing the following effects....
Asthma
• The lining of these airways becomes inflamed.
• The cells of the epithelial lining secrete larger quantities of
mucus than normal.
• Fluid leaves the capillaries and enters the airways.
• The muscle surrounding the bronchioles contracts and so
constricts the airways.
Asthma
Causes
Genetics appears to play a role, as asthma tends to run in families.
The number of asthmatics continues to rise and many explanations
have been put forward for this;
• Increase in air pollution.
• Increase in stress levels.
• Increase in chemicals used in food and other manufactured
products.
• Our now ‘cleaner’ lifestyles means we are exposed to fewer
allergens and therefore don’t build up a tolerance to them.
Asthma
Symptoms
Difficulty in breathing due to the constriction of the bronchi and
bronchioles, their inflamed linings and the additional fluid and
mucus within them.
A wheezing sound when breathing caused by the air passing
through very constricted bronchi and bronchioles.
A tight feeling in the chest is a consequence of not being able to
ventilate the lungs adequately because of constricted bronchi and
bronchioles.
Coughing is the body’s response to the obstructed bronchi and
bronchioles in an attempt to clear them.
Asthma
Emphysema
Description
One in every five smokers will develop emphysema. It develops over
a period of around 20 years or so, and it is virtually impossible to
diagnose until the lungs have been irreversibly damaged.
Healthy lungs contain large amounts of elastic tissue, mostly made
up of the protein elastin. This tissue stretches when we breathe in
and springs back when we breathe out.
In emphysematous lungs the elastin has become permanently
stretched and the lungs are no longer able to force out all of the air
from the alveoli. The surface area of the alveoli are reduced and
sometimes they burst. As a result, little if any exchange of gases can
take places across the surface of the stretched and damaged sacs.
Emphysema
Causes
Emphysema is almost always caused by smoking tobacco. A few
cases have been found to have other causes, and these will be
known as secondary emphysema.
The only way at all to minimise the changes of developing
emphysema is to not smoke at all.
Emphysema
Symptoms
Shortness in breath results from difficulty exhaling air due to loss of
elasticity in the lungs. If the lungs cannot be emptied, then it is even
more difficult to inhale fresh air containing oxygen and so the
patient feels breathless.
Shallow, rapid breathing due to the smaller alveolar surface area
resulting in a reduced intake of O2. The patient tries to increase
intake of O2 by breathing more rapidly.
Chronic cough is the consequence of lung damage and the body’s
effort to remove damaged tissue and mucus that cannot be
removed naturally because the cilia have been destroyed.
Bluish skin colouration due to low levels of O2 in the blood.
Emphysema
Emphysema
Emphysema
Emphysema
Emphysema
Respiratory diseases
Respiratory diseases are one of the biggest causes of death
worldwide.
Respiratory diseases affect the lungs, bronchi, trachea and
throat. They can be mild (e.g. cold) or life-threatening (e.g.
pneumonia, lung cancer).
Chronic obstructive pulmonary disorder (COPD) is a
term for a group of diseases that cause a reduction in the
airflow in the lungs and which are not fully reversible.
Two of the more serious types of COPD are chronic
bronchitis and emphysema, and are both usually caused
by smoking.
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COPD: chronic bronchitis
Chronic bronchitis is a
narrowing of the bronchi. It
is characterized by:


a persistent cough that
produces phlegm - due
to an increased number
and size of goblet cells
bronchi
normal
airway
mucus
inflammed
airway
shortness of breath and wheezing - irritants in cigarette
smoke cause inflammation in the lining of the bronchioles.
Over time this leads to scarring and narrowing of the
bronchioles, reducing airflow.
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COPD: emphysema
Emphysema is a gradual breakdown of alveolar walls and
damage to terminal bronchioles and alveolar capillaries.
This reduces the efficiency of gas exchange, causing
chronic breathlessness and hyperventilation.
Using this photo of
healthy lung tissue
(left) and emphysema
lung tissue (right), can
you explain why gas
exchange is less
efficient in
emphysema?
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Diagnosing COPD
There is no one single test for COPD. Diagnosis depends
on taking into account a patient’s risk factors (e.g. whether
they smoke, their age), their symptoms and clinical tests.
Testing the patient’s lung
function using spirometry
is essential. It can
determine whether there is
airway obstruction and can
help exclude the possibility
of other respiratory
diseases, such as asthma
or lung cancer.
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Determining lung function
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Treating COPD
Stopping smoking is the single most important step in
slowing the decline in lung function in people with COPD.
Medicines commonly prescribed to treat COPD include
bronchodilators, which widen the airways by relaxing
smooth muscles, and corticosteroids, which act as antiinflammatories.
Oxygen therapy,
especially for people
with emphysema, may
be required for most of
each day.
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What is asthma?
Asthma is a chronic condition in which the airways
occasionally narrow and become inflamed, limiting airflow.
Asthma causes difficulty
breathing, wheezing and
chest tightness, and can
be mild or life-threatening.
Asthma is triggered by a
range of stimuli, such as
allergens, dust, exercise,
stress and infections.
Treatment is with bronchodilators, corticosteroids, or a
combination of the two.
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Lung cancer
Lung cancer is the biggest cause of cancer-related deaths in
men and second-biggest cause in women. About 90% of
cases are caused by smoking.
Most incidences of lung
cancer are due to
uncontrolled growth of
epithelial cells lining the
airways. Cancers arising
from these cells are
called carcinomas.
Symptoms include shortness of breath, coughing (including
coughing up blood) and loss of weight.
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Lung cancer
Lung cancer generally develops quite slowly. By the time it
has been diagnosed, the cancer may have spread to other
areas of the body. This is called metastasis, and makes it
difficult to treat successfully.
Lung cancer can be seen
on an X-ray or a CT scan,
and diagnosis is usually
confirmed after a small
sample of tissue is taken
(a biopsy) and analysed.
Like many other cancers, lung cancer is treated by surgery,
chemotherapy and/or radiotherapy.
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Cancer statistics
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Smoking and lung cancer
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Smoking and lung cancer: epidemiology
The first solid epidemiological evidence that smoking
increased the risk of lung cancer came from a 1950 study by
Richard Doll, a British doctor and epidemiologist, and Austin
Bradford Hill, a British epidemiologist and statistician.
Before their study, it was unclear whether the rapid rise in
lung cancer was due to smoking or other atmospheric
pollution, such as exhaust fumes, industrial plants or tarmac.
Their study of over 1,700 men and women in London
concluded that: “The risk of developing the disease
increases in proportion to the amount smoked. It may be
50 times as great among those who smoke 25 or more
cigarettes a day as among non-smokers.”
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Smoking and health: epidemiology
Following Doll and Hill’s research, a large-scale study into the
health and smoking habits of British male doctors began in
1950, continuing with periodic updates until 2001.
Two of the main findings of this British Doctors Study were:

life-long smokers died, on average, 10 years earlier than
non-smokers

the earlier smokers stop smoking, the more chance they
have of avoiding reduced life expectancy.
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Which respiratory disease?
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