The greatest machine you’ll ever own is your human body. It’s more complicated than any computer, it lasts for a lifetime, and it’s yours for free.

Body parts

Your body is made up of hundreds of different parts. You probably know the names of the bits you can see, but there are many more hidden deep inside you.

Inside your body
Doctors can see many more hidden inside your body with special cameras. X-ray cameras take pictures of hard body parts like bones. Other cameras, called scanners, can see soft body parts.

Two of everything
Body parts often come in pairs. You have two feet, two eyes, two ears, two lungs, and so on. This means you have a handy spare in case one of them gets damaged.

Water, water, water is the most important chemical in your body. About two-thirds of your weight is water.

No substitute
The human body is too complicated for robots to copy. Robots can copy the way we walk, but they can’t think or feel like we do.

The ingredients
Your body is made of just a few simple chemicals, plus water.
  • Carbon is the chemical in diamonds and coal. A fifth of you is carbon.
  • Iron makes your blood red. You have enough to make one small iron nail.
  • Phosphorus is in the tips of matches, as well as your bones and teeth.
  • Sodium and chlorine make salt. Blood is one-third as salty as sea water.
  • Potassium is used in some types of soap. It’s also in your body fluids.
  • Nitrogen is important in muscles. It’s also the main ingredient in air.

Although we look different to animals, our bodies are similar on the inside. Our closest animal relatives are chimpanzees.

What makes you you?
All human bodies work the same way, but everyone is different. Nobody looks, sounds, or thinks exactly like you. You’re different because of the way your genes and experience shape you as you grow up.

Unique, the shape of your face, the colour of your hair, and many other things make you unique different from everyone else.

In the genes
Genes are instructions that build your body and tell it how to work. Your genes control many of the things that make you unique, like the colour of In the family.
Your genes came from your parents. Half come from your mother and half come from your father. If you look like your parents, it’s because you share the same genes. Your genes are stored in a chemical called DNA, which looks like a twisted ladder with four different types of rung. The rungs make up a four-letter alphabet that spells out your genes, like letters in a book. your eyes or how tall you’ll be.
Genes don’t control everything – experience also shapes you. If you exercise a lot, for instance, your body gets stronger.

Building blocks
Every part of your body is made of tiny building blocks called cells, which fit together like bricks in a wall. Cells are so small that hundreds could fit on the point of a pin. Inside a cell In the middle of a cell is its control centre – the nucleus. The nucleus sends instructions to the rest of the cell, telling the cell what chemicals to make.
A cell makes new cells by dividing. The two new cells are half the size, but they soon grow back. Millions of your cells die every second, but millions of others divide to replace them.

How big are cells?
Cells are too small to see with the naked eye, but scientists can photograph them through powerful microscopes. The cells on your skin are about a hundredth of a millimetre wide.
Cells make tissue. Your body contains hundreds of different types of cells that do different jobs. Cells of the same type usually group together to form tissue. Fat, muscle, bone, and nerves are types of tissue. Blood is a liquid tissue.

Organizing the body
Your cells and tissues are organized into larger body parts called organs. In turn, your organs work together to form body systems.
An organ is a body part that does a specific job. Your heart’s job, for instance is to pump blood. Kidneys clean blood.
If a vital organ stops working, doctors may replace it with an organ from another person. This is called a transplant.
Systems Organs and tissues work in teams to carry out major tasks, like transporting blood or processing food. These teams are called systems.

Your heart, blood, and blood vessels make up the blood system. It transports vital supplies around your body.

Your muscle system is made of tissues that move parts of your body by pulling on them or squeezing them. Your biggest muscles all pull on bones.

Your nervous system carries electrical signals around your body. You need this system to see, hear, think, and react.

Other systems
Some of your other important systems are shown in this list.
  • Breathing system: the main organs are your lungs, which take in air.
  • Hormone system: this uses powerful chemicals to control your body and mood.
  • Skin, hair, and nails: these form your body’s protective covering.
  • Immune system: this seeks and destroys germs that get into your body.
  • Urinary system: this cleans blood and gets rid of waste chemicals.
  • Reproductive system: these are the organs that make babies.

Your digestive organs break down food to provide your body with energy and raw materials. So, those are some clue about your human body and there are a lot of things that you don't know yet.

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