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Smoking can cause lung disease, heart disease and certain cancers.

Nicotine is the addictive substance in tobacco. It quickly reaches the brain and creates a dependency so that smokers become addicted.

Effects on the air passages

Sticky mucus in the lungs traps . The mucus is normally swept out of the lungs by the on the lining the trachea, and . However, cigarette smoke contains harmful chemicals that damage these cells, leading to a build-up of mucus and a smoker's cough. Smoke irritates the bronchi, causing bronchitis .

Effects on the alveoli

Smoke damages the walls of the . The alveoli walls break down and join together, forming larger air spaces than normal. This reduces the efficiency of gas exchange, so people with the lung disease (a type of COPD or chronic obstructive pulmonary disease) carry less oxygen in their blood and find even mild exercise difficult.

Carbon monoxide

Carbon monoxide, CO, combines with the in red blood cells. This reduces the ability of the blood to carry oxygen, putting strain on the and increasing the risk of coronary heart disease and strokes.

Lung cancer

Carcinogens are substances that cause cancer. Tobacco smoke contains many carcinogens, including tar. Smoking increases the risk of lung cancer, and cancer of the mouth, throat and oesophagus.

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Respiratory system - Revision 5 - GCSE Biology (Single Science) - BBC Bitesize

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Smoking can cause lung disease, heart disease and certain cancers. Nicotine is the addictive substance in tobacco. It quickly reaches the brain and creates a dependency so that smokers become addicted. Sticky mucus in the lungs traps . The mucus is normally swept out of the lungs by the on the lining the trachea, and .

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GCSE Biology Revision "Lifestyle and Disease"