In this IBDP Biology topic, you will learn the cause and effect of some lungs diseases.

Tuberculosis (TB) is an infectious disease 

• effects any part of the body; usually the lungs at first site.
• 2 million killed each year – more than any other infectious disease

Causes:

• Rod-shaped bacteria; Mycobacterium Tuberculosis or Mycobacterium Bovis
• 30% of world’s population have bacteria within body.

Symptoms:

• Persistent cough
• Tiredness / loss of appetite / weight loss
• Fever
• Coughing up blood

• Spread through the air by droplets, cough, sneeze, laugh, talk.
• Mycobacterium Tuberculosis – resistant bacterium that can survive weeks, even when dried out.
• Close contact over a period of time to transmit the bacteria.
• Usually spread between families, friends and work colleagues. Especially crowded and poorly ventilated conditions.
• M.Bovis can spread from cows to humans in milk.

• Close contact/overcrowding
• Work/live in care facilities, care homes, prisons, old people’s home, hospitals.
• From countries where TB is present
• Reduced immunity

• Bacteria grow/divide within upper region of lungs – plenty of O2.
• Immune system response; white blood cells accumulate (gather) at site of infection to ingest bacteria.
• Inflammation & enlargement of lymph nodes that drain that area of lungs. Called primary infection (usually children)
• Healthy person – few symptoms – infection controlled, but bacteria remain.
• Post-primary tuberculosis – occurs in adults many years later – bacteria re-emerge; cause 2nd infection.
• Arises upper region of lungs – not easily controlled.
• Bacteria destroy lung tissue → cavities / scar tissue.
• Cough – damaged lung tissue + blood → spread around body – death!

• Biological control – Vaccination; attenuated (weakened) strain of M. Bovis; UK children screened.
• Social/economic measures – better education (completion of drugs); more/better housing; improved health facilities/treatments; better nutrition – healthier immune system.
• Drug treatment – long period 6-9 months – resistant M. tuberculosis.
• ↑ HIV spread, drug resistance; ↑ elderly; ↑ homeless

• Normal tissue is damaged
• Scars form on epithelium
• Alveoli walls becomes more thickened
• Gas exchange more difficult

• Chronic (long term),dry cough-fibrosis creates an obstruction
• Shortness of breath (especially during exercise)- volume of lungs is decreased by fibrous tissue. Diffusion pathway increased
• Pain/discomfort in chest- pressure from fibrous tissue, damage from coughing
• Weakness & Fatigue- lack of oxygen to blood reduces respiration

• Not clear
• Work related E.g. asbestos/miners
• Radiation- from cancer treatment
• Chronic conditions- rheumatoid arthritis
• Smoking

• Localised allergic reaction
• Triggers; pollen, fur, dust mite faeces, air pollution, cold air, exercise, anxiety, stress.
• Possible link to other allergies E.g. hay fever and eczema
• Genetic link
• Exposure to fewer allergens/over sensitised

• Allergens cause white blood cells on lining of lungs to release a chemical called histamine
• Lining of airways is inflamed
• Epithelial cells release more mucus
• Fluid from capillaries enters airways
• Muscle of bronchioles contracts

• Difficulty breathing- constriction of bronchi & bronchioles, additional mucus & fluid
• Wheezing-due to constricted airways
• Tightness in chest-unable to ventilate lungs sufficiently
• Coughing-reflex response to constricted airway

• Shortness of breath-difficult to exhale air
• Chronic cough- lungs efforts to remove damaged tissue
• Bluish skin colour- low levels of oxygen in blood due to poor gas exchange

• Elastin of lungs is damaged
• Lungs no longer recoil and expel air
• SA of alveoli reduced
• Gas exchange is reduced
• One in 20 smokers
• Develops over 20 years
• Diagnosed once damage is done
• Irreversible

• Smoking-90% of emphysema sufferers are smokers
• Air Pollution- heavy industry
• Genetics-some people are more likely to get lung disease
• Infection-higher risk of lung infections, higher risk of lung disease

This is the end of the topic

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Drafted by Eva (Biology)

Photo references:

1. https://www.everydayhealth.com/tuberculosis/guide/risk-factors-causes-prevention/
2. https://en.wikipedia.org/wiki/Idiopathic_pulmonary_fibrosis
3. https://www.everydayhealth.com/hs/asthma/complications-uncontrolled-asthma/
4. https://www.drugs.com/health-guide/emphysema.html