Human Respiratory System
Primary 6 · Science and Elementary Technology
Human Respiratory System
Lesson 1 of 5
15 min
Let's begin
After a fast game of football at break, Ishimwe drops onto the bench. His chest rises and falls quickly and he can hear himself breathing.
"Where does all that air go?" he asks his friend Mutesi. "It goes into your lungs," she says. "But how does it get there?"
Today you will follow one breath of air on its journey into your body.
The respiratory system is the group of organs that takes air into your body and lets it out again. Its main job is to bring oxygen into the body and to remove carbon dioxide.
Every cell in your body needs oxygen to release energy from the food you eat. When cells do this, they make carbon dioxide, a waste gas the body must get rid of. The respiratory system works closely with the circulatory system: the blood carries the oxygen from the lungs to every cell, and brings the carbon dioxide back.
The two lungs sit in your chest, protected by the rib cage. They are soft and spongy, not empty bags. They are packed with millions of alveoli and the tubes that lead to them.
Under the lungs is the diaphragm, a dome-shaped sheet of muscle that separates the chest from the belly. It is the main muscle you use to breathe. You will see how it works in the next lesson.
| Organ | Main job |
|---|---|
| Nose | Lets air in; traps dust and germs; warms and wets the air |
| Trachea (windpipe) | Carries air from the throat to the bronchi; kept open by cartilage rings |
| Bronchi | Carry air into the left and right lungs |
| Bronchioles | Carry air to every part of the lung |
| Alveoli | Air sacs where oxygen enters the blood and carbon dioxide leaves it |
| Lungs | Hold the bronchioles and alveoli |
| Diaphragm | Muscle under the lungs that makes breathing happen |
Tip
Think of an upside-down tree
The trachea is the trunk. The two bronchi are the big branches. The bronchioles are the small twigs. The alveoli are the leaves at the very tips, where the work gets done.
Say it five times: nose, trachea, bronchi, bronchioles, alveoli.
Try each one on your own first, then tap Show answer to check.
Put these in the order that air passes through them: bronchioles, nose, alveoli, trachea, bronchi.
Answer: nose, trachea, bronchi, bronchioles, alveoli.
Why does the trachea have rings of cartilage?
Answer: To keep it open all the time, so air can always pass through.
In which part of the lungs does oxygen pass into the blood?
Answer: In the alveoli, the tiny air sacs at the ends of the bronchioles.
What is the name of the muscle under the lungs?
Answer: The diaphragm.
Gatete says the lungs are two empty bags, like balloons. Is he right?
Answer: No. The lungs are spongy and packed with millions of tiny air sacs (alveoli) and tubes.
What you learned today
Sources and credits
Quick check
Follow one breath of air into the body. Put these in order.
Tap the cards in the right order.
