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The alveoli are the site of gas exchange in the lungs. Oxygen diffuses into the blood down a concentration gradient while carbon dioxide exits the lung by diffusion. Alveoli have a very large surface area as...

A stent is a small cylinder wire mesh that is inserted into the blood vessel and expanded. This opens the middle of the blood vessel , allowing greater blood flow, meaning more oxygen is delivered to the org...

The eye responds to bright light to protect the retina from damageThe bright light triggers a reflex that makes the pupils smaller, meaning less light enters the eyeAs with all reflexes, there is a stimulus,...

Over fertilisation is heavily linked to leeching and eutrophication. By adding more fertilisers and minerals to the soil, the soil is more likely to become saturated. Therefore, when it rains, the soluble fe...

Pathogens can cause diseases. We can prevent a pathogen from causing a disease in an individual by giving them a vaccine which can make them immune to the pathogen. We do this by taking a dead/weakened form ...