A chemical reaction which releases energy from food
Respiratory system
Exchanges the gases which are involved in respiration
Smoking can cause lung disease, heart disease and certain cancers
Nicotine
The addictive substance in tobacco
Nicotine reaches the brain
Creates a dependency so that smokers become addicted
Effects of smoking on the air passages
Sticky mucus in the lungs traps pathogens
Mucus is normally swept out by cilia on epithelial cells lining the trachea, bronchi and bronchioles
Cigarette smoke contains harmfulchemicals that paralyse the cilia, leading to a build-up of mucus and a smoker's cough
Smoke irritates the bronchi, causing bronchitis
Effects of smoking on the alveoli
Smoke damages the walls of the alveoli
The alveoli walls break down and join together, forming larger air spaces than normal
This reduces the ability of the blood to carry oxygen, putting a strain on the heart which increases the risk of developing coronary heart disease or strokes
Carbon monoxide
Combines with haemoglobin in red blood cells, reducing the ability of the blood to carry oxygen, putting a strain on the heart
Carcinogens
Chemicals or other agents that cause cancer
Smoking increases the risk of lung cancer, and cancer of the mouth, throat and oesophagus
