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Lung and Heart Disease…read more

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Pulmonary Tuberculosis
· Caused by one of two species of rod-shaped
Mycobacterium tuberculosis or Mycobacterium
· Symptoms of TB include:
-a persistent cough
-loss of appetite, leading to weight loss
· Tuberculosis is spread via droplets in the air.
Mycobacterium tuberculosis can survive for
weeks however, even once the droplets have
dried.…read more

Slide 3

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Pulmonary Tuberculosis
· Once the bacteria has entered the body, they grow and divide in the
upper regions of the lungs, where there is a large amount of oxygen
· The immune system responds by sending white blood cells to the
site of infection, which ingest the bacteria
· This causes inflammation and enlargement of the lymph nodes
which drain that particular area of the lungs ­ primary infection
· At this stage there are very few symptoms, although some bacteria
usually remain in the body
· The bacteria may re-emerge to cause a second infection, but this
could happen years later ­ post-primary infection
· The infection arises again in the upper regions, but is not so easy to
· Bacteria destroy the lung tissue, resulting in cavities and scar tissue
· Sufferer coughs up damaged lung tissue containing the bacteria, as
well as blood.
· If untreated, the TB can spread to the rest of the body, and can be
fatal.…read more

Slide 4

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Pulmonary Tuberculosis
· The main prevention of TB is vaccination
· However, there are other measures that can be taken to
reduce the number of cases too, particularly in less
economically developed countries, including an increase
in the number and quality of housing, health facilities,
and education about TB, especially the need to complete
all drug courses and ensure that the immune system is
not weakened by a poor diet.
· TB can also be treated with drugs, although these must
be taken over a long period of 6-9 months
· Some strains of the mycobacterium however, are no
longer responsive to some drugs…read more

Slide 5

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Pulmonary Fibrosis
· Scars form on the epithelium of the lungs, causing irreversible thickening
· According to Fick's law, this reduces the rate of diffusion, as the diffusion
pathway has been increased, and the lung capacity has been decreased.
· This also causes reduced elasticity of the lungs, which makes it more
difficult to breathe
· Symptoms include:
­ Shortness of breath, particularly when exercising, as the rate of diffusion of
oxygen across the alveoli is decreased
­ A chronic, dry cough, as the body's natural response to the obstruction caused
by the fibrous scar tissue is to try and cough it out
­ Pain/discomfort in the chest, as there is greater pressure from the mass of
fibrous tissue, and further damage and scarring from the coughing
­ Weakness and fatigue, as less oxygen is entering via gaseous exchange, so
the rate of respiration decreases, meaning the body is supplied less energy,
causing a feeling of tiredness
· The cause of fibrosis is unclear, but believed to be a reaction to microscopic
lung injury.
· Pulmonary fibrosis is very difficult to treat, and can lead to many other
medical complications…read more

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· Asthma is a localised allergic reaction, and affects roughly 10% of the world's
· Some common allergens that trigger asthma include pollen, fur, the faeces of the
house dust mite, and air pollutants, although it can also be triggered by exercise, cold
air or stress.
· One or more of these factors causes white blood cells in the linings of bronchi and
bronchioles to release a chemical called histamine.
· Histamine causes the following effects:
­ Lining of airways becomes inflamed
­ Epithelial cells secrete larger amounts of mucus than usual
­ Fluid leaves capillaries and enters airways
­ The muscle surrounding the bronchioles contracts, constricting the airways.
· All of this causes a great amount of resistance against ventilation, and so makes it
difficult to maintain a diffusion gradient across the exchange surface in alveoli.
· Symptoms of this include:
­ Difficulty in breathing, due to the added resistance
­ A wheezing sound when breathing, caused by air passing through the very constricted
­ A tight feeling in the chest, as a consequence of not being able to adequately ventilate
­ Coughing, in an attempt to clear the blocked airways
· Asthma tends to run in families, and so there is a link to genetics
· There are many treatments for asthma, including inhalers, medications and steroids…read more

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