Today we are covering from the specification: Pages 82 to 85 of your textbook.

Today we are covering from the specification:

Pages 82 to 85 of your textbook

Pulmonary TuberculosisVideo

- Course of infection- Symptoms- Transmission

http://stoptb.org/assets/videos/hfotb/

What is the cause of pulmonary TB?

• Tuberculosis is caused by one of two rod-shaped 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

6 of 45 © Boardworks Ltd 2008

Tuberculosis infection

When a person becomes infected with TB, an immune response is produced.

However, the bacteria can survive inside macrophages for years until the immune system becomes weak.

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.


Symptoms of tuberculosis

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.

Why might an increase in temperature be harmful?

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.

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.

Course of Infection

Primary 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.

TB and HIV

Try the questions.

http://www.youtube.com/watch?v=Gh2Ovh0uAss

Pulmonary fibrosis

http://www.youtube.com/watch?v=Gh2Ovh0uAss

Recap from last lesson....1. What is pulmonary tuberculosis?2. What is it caused by?3. How is it transmitted?4. How does it affect the lungs?5. 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 FibrosisDescriptionHappens 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.

CauseThe 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 FibrosisSymptomsShortness 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

AsthmaDescriptionAsthma 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.

AsthmaCausesGenetics 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.

AsthmaSymptomsDifficulty 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

EmphysemaDescriptionOne 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.

EmphysemaCausesEmphysema 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.

EmphysemaSymptomsShortness 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.


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

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.

normal airway

inflammedairway

mucus

bronchi


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?


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.


Determining lung function


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 anti-inflammatories.

Oxygen therapy, especially for people with emphysema, may be required for most of each day.


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.

Treatment is with bronchodilators, corticosteroids, or a combination of the two.

Asthma is triggered by a range of stimuli, such as allergens, dust, exercise, stress and infections.


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.

Symptoms include shortness of breath, coughing (including coughing up blood) and loss of weight.

Most incidences of lung cancer are due to uncontrolled growth of epithelial cells lining the airways. Cancers arising from these cells are called carcinomas.


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.


Cancer statistics


Smoking and lung cancer


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.

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.”

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.


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.


Which respiratory disease?

Today we are covering from the specification: Pages 82 to 85 of your textbook.

Documents

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