Cosmos

The Human Body

You are 37 trillion cells organised into a skeleton, muscles, organs and a brain that is reading this sentence. These readings take the body apart system by system and explain how each one works.

10 articles · about 39 minutes of reading

The Human Body

Digestion

A nine-metre tube turns a sandwich into the molecules that build and fuel you, with help from acids, enzymes and trillions of bacteria.

Article · 4 min read

The Human Body

Lungs and Breathing

Twenty thousand times a day you draw in air and your lungs, with a surface the size of a tennis court, pass oxygen into your blood. Here is how breathing works.

Article · 4 min read

The Human Body

Muscles

Six hundred muscles move you, pump your blood and push your food along. Every one of them works the same way: by pulling, never pushing.

Article · 4 min read

The Human Body

Skin, Hair and Nails

Your skin is your largest organ: a waterproof, self-repairing shield that senses touch, controls your temperature and makes vitamin D. Hair and nails grow from it.

Article · 3 min read

The Human Body

Sleep and Dreams

We spend about a third of our lives asleep. Far from switching off, the brain uses that time to store memories, clean itself and reset the body.

Article · 3 min read

The Human Body

The Brain

A kilo and a half of soft tissue containing 86 billion neurons and more connections than there are stars in the galaxy. It is reading this, and it is the most complex object known.

Article · 4 min read

The Human Body

The Heart and Blood

A fist-sized pump pushes five litres of blood around 100,000 kilometres of vessels every minute. Here is the river that keeps every cell alive.

Article · 4 min read

The Human Body

The Immune System

An army of trillions of cells defends you against invaders you never notice, learns from every battle and remembers for decades. Vaccines train it; sometimes it turns on you.

Article · 4 min read

The Human Body

The Senses

Sight, hearing, smell, taste and touch are the body's instruments for turning light, vibration and chemistry into experience. There are more than five, and all of them are built in the brain.

Article · 4 min read

The Human Body

The Skeleton and Bones

Your 206 bones are living tissue: they grow, heal, make your blood and rebuild themselves completely every decade. Here is the frame you are built on.

Article · 5 min read