The Body, For Real
The living machine you actually are The Nervous System · DNA & Cells · The Immune System · Hormones & Growing Up · The Heart & Blood · Muscles & Movement. Right now, without you thinking about it, your body is running millions of chemical reactions a second.
Ages 14–16
What's inside
The Nervous System — your body's internet
Every thought you have, every move you make, every feeling that hits you is electricity and chemistry running through a network of nerve cells. The nervous system is your body's control centre and messaging network rolled into one: the brain and spinal cord give the orders, and nerves carry them to and from every corner of you, faster than you can notice.
DNA & Cells — your instruction manual
You are built from around 37 trillion tiny living units called cells, and inside almost every one sits a complete copy of your instruction manual: your DNA. It is a molecule shaped like a twisted ladder, and the order of its four chemical 'letters' spells out every recipe your body needs — from your eye colour to the exact shape of the proteins keeping you alive.
The Immune System — your invisible army
Every day you breathe in, touch and swallow millions of bacteria, viruses and fungi that would happily use your body as food. The reason you are usually fine is a defence force patrolling every part of you: the immune system. It tells 'you' from 'not you', hunts down invaders, remembers the ones it has met, and mostly does all of it without you ever noticing.
Hormones & Growing Up — the chemical messengers
Hormones are chemical messages your body releases into the blood to tell distant organs what to do. A tiny amount can change how you grow, sleep, feel hungry, feel stressed — and, during your teens, they are quietly running one of the biggest transformations a human body ever goes through: turning a child's body into an adult one. If your moods and body feel like they have a mind of their own right now, this is largely why.
The Heart & Blood — the pump that never rests
Your heart is a fist-sized muscle that has been beating since before you were born and will not stop for your entire life — no rest days, no breaks. It pushes blood through a network of vessels so long it could wrap around the Earth more than twice, delivering oxygen and fuel to all 37 trillion of your cells and carrying away their waste, on a loop that takes about one minute.
Muscles & Movement — how you move a body
You cannot do a single thing — walk, blink, smile, breathe, even read this — without muscles. They are the only way your body turns the electrical decisions of your brain into actual movement in the real world. And unlike almost any machine, muscle is alive: use it and it grows, ignore it and it shrinks, which means the body you have is partly one you are building.
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