Pneumonia Lesson for Kids

Instructor: Lindsy Frazer

Dr. Frazer has taught several college level Science courses and has a master's degree in Human Biology and a PhD in Library and Information Science.

Has someone warned you not to play outside in the cold without a jacket and said you will catch pneumonia? In this lesson, you will learn what pneumonia is, what causes pneumonia (hint: it isn't cold air!), and pneumonia's symptoms.


Take a long, deep breath. Can you feel your chest getting bigger? As you breathe in, your lungs fill with air - just like two big balloons! But the air doesn't just hang around in the lungs; oxygen from the air is passed through parts of the lungs called alveoli and into the blood.

Alveoli are the parts of our lungs that pass oxygen from the air we breathe into our blood so that it can be transported throughout our body.

Alveoli are tiny sacs of air covered in tiny blood vessels. When the air we breathe in makes it to our alveoli, the oxygen in that air passes through the thin walls of the alveoli and into the blood vessels covering it. Your blood then transports this oxygen all over your body. Every part of your body from your toes to your nose needs oxygen to work.

Oxygen passes through the walls of the alveoli and into the blood vessels.

What happens when the drain in your sink gets clogged? Water has a difficult time getting down the drain. Our lungs have millions of alveoli that work every time we breathe to transfer oxygen to our blood, but what do you think happens to that blood if alveoli get clogged?

Pneumonia is a common cause of clogged alveoli.

What is Pneumonia?

Achoo! Think about the last time you had a stuffy nose. It was probably hard to breathe through your nose because of all the mucus-y, slimy snot. Yuck!

If a person has pneumonia, an infection of the lungs, the walls of their alveoli become inflamed, or swollen, and they fill with mucus and fluid like your nose does when you have a cold. This inflammation and mucus clog up the alveoli, making it hard for oxygen to move through the lungs and into the blood vessels.

Pneumonia causes the alveoli to fill with mucus and fluid.

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