RESPIRATORY SYSTEM
Ventilation – Movement of air into and out of the lungs in two stages: inspiration and expiration – controlled by the movement of ribcage and diaphragm
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Gas exchange – Diffusion of oxygen and carbon dioxide to and from the blood at the alveoli and the respiring tissue
Cell respiration – Production of ATP at cellular level at mitochondria
ALVEOLI
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Increases surface area to volume ratio for gas exchange
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Each surrounded by rich network of capillaries
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High concentration gradient of oxygen and carbon dioxide
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Thin membrane of blood capillaries and alveoli
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Short diffusion path
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Surfaces are wet – gases are dissolved
TYPE 1 PNEUMOCYTE – Gas exchange
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TYPE 2 PNEUMOCYTE – Secretes surfactant to prevent sides of alveolus adhering
ASTHMA – Causes airways to narrow and swell
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Environmental and genetic factors
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Inhalers contain hormones which relax bronchi muscles to open up and allow air to flow normally, during asthma attack
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LUNG CANCER
Most common form of cancer
Difficult to treat and high mortality rate
Vast majority of lung cancers caused due to smoking
Causes of lung cancer:
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Asbestos dust particles lodge in the lungs and cannot be broken down
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Smoking (cigarettes, cigars, pipe tobacco)
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Passive smoking (breathing in someone else's cigarette smoke); about 3% of all cases
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Air pollution: diesel exhaust fumes contain many carcinogens (compounds causing cancer)
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Radon gas: in some parts of the world there is a higher concentration of this radioactive gas. It emits alpha particles, which can cause mutations when inhaled.
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EMPHYSEMA
Caused by long term exposure to cigarettes and other pollutants
Narrowing of small airways and breakdown of lung tissue
Alveoli become less elastic, making ventilation more difficult