What is inside my body, and how do all the parts work together?
Your guess
Pick one before you read on. It is fine to be wrong.
By the end you can
Name the main organ systems and one organ in each
Explain how two systems work together when you run
Your body is not one lump. It is made of parts, and each part has its own job. Build the picture below one step at a time.
Draw it first
Draw the inside of the body
1 Draw the head, the arms, the trunk and the tops of the legs. Leave the inside empty.
2 Put in the two lungs. Put the heart between them, a little to the left of the middle.
3 Add the liver on the right, the stomach on the left, and the intestines below.
4 Add the brain in the head, the two kidneys and the bladder.
The body in the picture faces you. So its left side is on the right of the page. Its right side is on the left.
An organ is a part of the body with one main job. The heart is an organ. So are the lungs, the stomach and the brain.
Organs work in teams. A team of organs that does a big job together is an organ system.
The digestive system breaks food down. The stomach and the intestines are part of it.The lungs belong to the breathing system, which takes in air. The heart belongs to the circulatory system, which moves blood.The brain is in the nervous system, which sends signals. The kidneys and the bladder are in the excretory system, which removes waste liquid. The kidneys lie at the back, one each side of the spine.
Two more systems are not in the picture. One is the reproductive system, for making new life. You can read about it in the book Growing up. The other is the skeleton and the muscles, below.
The skeleton and the muscles make the skeletal and muscular system. It holds you up and moves you. The skull guards the brain. The ribs guard the heart and lungs.
See it three ways
With things
If you are well, run on the spot for one minute. Your chest moves faster and your heart beats faster. Your muscles feel warm.
As a picture
In words
The lungs take oxygen from the air. The heart pushes the blood round the body. The blood carries the oxygen to the muscles. Three systems work as one team.
Try it
Feel your body at work
You need: your own body, a quiet place to sit.
Be safe: Stop at once if you feel dizzy or have any pain. If you have a heart or breathing illness, ask a health worker before you run.
Sit still. Put one hand flat on your chest, a little to the left of the middle. Feel the beat of your heart.
Breathe in slowly. Feel your ribs move up and out under your hand.
If you are well, jog on the spot for 30 seconds. Then feel your chest again.
What you will see: After jogging your heart beats faster and you breathe faster. Two systems speed up together.
If you cannot try it, this is what happens.
A wrong idea many people have
Each organ does its job alone.
Why it feels right: Every organ has its own name, its own place and its own job.
The test that breaks it: Think of running. The muscles need oxygen from the lungs. The heart must carry it there. If any one of them stopped, the runner would have to stop.
What is true: Organs work in teams called systems, and the systems need each other.
Key words
organ
a part of the body with one main job, such as the heart or the lungs.
organ system
a team of organs that does a big job together.
Back to your guess
The answer is B: Organs work in teams, and the teams need each other.
Organs work in teams called systems. When you run, your lungs, heart and muscles all work together, so no part works alone.
Check yourself
Try each one before you look. A wrong answer tells you where to go next.
Which organ belongs to the digestive system?
See the answer
The stomach
The stomach breaks food down, so it is part of the digestive system.
If you chose B: The heart moves blood, so it is in the circulatory system. The digestive system handles food. Go to S3.3.1.
If you chose C: The brain sends signals, so it is in the nervous system. The digestive system handles food. Go to S3.3.1.
The kidneys remove waste liquid from the blood. Which system are they in?
See the answer
The excretory system
The excretory system removes waste. The kidneys and the bladder are in it.
If you chose A: The breathing system takes in air. It does not make waste liquid. Go to S3.3.1.
If you chose C: The skeletal system is the bones. Kidneys are soft organs with another job. Go to S3.3.1.
What is an organ system?
See the answer
A team of organs that does a big job together
The stomach, the liver and the intestines are a team. They make up the digestive system.
If you chose A: Each organ has one main job. A system is a team of organs. Go to S3.3.1.
If you chose C: Bones are one system, but a system is any team of organs, not only bones. Go to S3.3.1.
Maya runs to catch a bus. Which two systems bring oxygen to her muscles?
See the answer
The breathing system and the circulatory system
The lungs of the breathing system take in oxygen. The heart and blood of the circulatory system carry it to the muscles.
If you chose B: The digestive system handles food. Oxygen comes in with the air we breathe and moves in the blood. Go to S3.3.1.
If you chose C: Bones hold the body up and the excretory system removes waste. Neither carries oxygen. Go to S3.3.1.
Why does your heart beat faster when you run?
See the answer
The muscles need more oxygen, so the heart sends more blood
Working muscles use oxygen quickly. A faster heart sends them more blood, and the blood brings more oxygen.
If you chose A: Excitement can speed the heart, but running does it too. Your muscles need more oxygen, and the heart must carry it. Go to S3.3.1.
If you chose C: The lungs do not squeeze the heart. The heart is a muscle that beats by itself, faster when the body needs more. Go to S3.3.1.
Keep it
Copy this into your exercise book.
An organ has one main job. A team of organs is an organ system. Systems need each other. Running uses the lungs, the heart and the muscles together.
Draw: Draw a standing person. Put in the lungs, the heart, the stomach and the brain, and label each one.
