How your body works, explained
Plain-English explanations of how your body works, with clear illustrations, the key facts first and the sources on every page.
How your body makes energy, and why you feel tired
Your cells turn glucose and oxygen into energy. How it works in 5 steps, the common reasons you feel tired, and when tiredness needs a doctor.
How sleep works
Two systems decide when you sleep: your body clock and a need for sleep that builds while you are awake. How a night of 4 to 6 sleep cycles works, and when poor sleep needs a doctor.
How your skin works
Your skin is your largest organ. How its three layers protect you, renew themselves and let you feel, and which moles and rashes need a doctor.
What happens during a migraine
A migraine attack usually lasts 4 hours to 3 days and can go through four phases. What happens in each one, the common triggers, and when a headache needs urgent help.
How your lymphatic system works
The lymphatic system returns about 3 litres of fluid a day from your tissues to your blood and filters it through about 600 lymph nodes. How it works in 5 steps, and when swollen glands need a doctor.
How your heart works
Your heart has four chambers and four valves and pumps blood in two loops, to your lungs and to your body. How each beat starts, and when chest pain is an emergency.
How your digestive system works
Your digestive tract is one long tube from mouth to anus, helped by the liver, gallbladder and pancreas. What happens at each step, what gut bacteria do, and when stomach pain is urgent.
How breathing works
Each breath carries air through branching airways into about 150 million tiny air sacs, where oxygen enters your blood. How it works, why you cough, and when breathing problems are urgent.
How your sense of balance works
Your balance comes from your inner ear, your eyes and sensors in your muscles and joints, combined by your brain. How it works, why you feel dizzy, and when dizziness is an emergency.
How your back and joints work
Your spine is 33 stacked vertebrae with cushioning discs, nerves, muscles and ligaments. How it works, how joints move smoothly, and when back pain needs urgent help.