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
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
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
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.
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