How You Breathe: The Journey of Air

Science · Organisms & Life Processes · ages 12-13

Name ______________________ Date ____________

What helps alveoli exchange gases so well?
- Thick walls and a small surface area
- Thin walls and a large surface area
- Thin walls and a small surface area
Which tube does air enter directly after leaving the trachea?
- Bronchi
- Bronchioles
- Alveoli
True or false: when you breathe in, the air pressure inside your chest becomes lower than the air pressure outside.
Circle one: True False
Why does air rush into your lungs when you breathe in?
- Muscles push the air in directly
- Chest volume increases, so pressure inside drops below the pressure outside
- Oxygen outside is heavier than the air already in your lungs
Put these in the order air actually travels through them.
- Trachea, bronchioles, bronchi, alveoli
- Trachea, bronchi, bronchioles, alveoli
- Bronchi, trachea, bronchioles, alveoli
Which feature would make gas exchange at the alveoli worse, not better?
- Thick, tough walls
- A large surface area
- A rich blood supply
A friend says the lungs have just a few large air sacs, and that's why gas exchange works so well. What's wrong with this?
- Gas exchange doesn't depend on surface area at all
- Large sacs would give the same surface area as many small ones
- It's millions of tiny alveoli, not a few large sacs, that create such a huge total surface area
If an injury stopped someone's ribs from moving outward, what would most likely happen to their breathing?
- Breathing would be unaffected
- It would be harder to lower the pressure inside the chest enough for a full breath
- Air would rush in even faster than normal

Answer key

For grown-ups. Fold this page away before handing over the rest.

How You Breathe: The Journey of Air W1-mt_V9SQS9gLFw-s1

Thin walls and a large surface area · Thin walls mean a short distance to cross, and a large surface area means more gas can cross at once.
Bronchi · The trachea splits into two bronchi, one going to each lung.
True · Your chest gets bigger, which drops the pressure inside, so outside air rushes in to balance it out.
Chest volume increases, so pressure inside drops below the pressure outside · A bigger chest means lower pressure inside, and air always moves from high pressure to low pressure.
Trachea, bronchi, bronchioles, alveoli · Air goes from the windpipe (trachea), into the bronchi, then the smaller bronchioles, ending at the alveoli.
Thick, tough walls · Thick walls make the distance gases have to cross longer, which slows diffusion down.
It's millions of tiny alveoli, not a few large sacs, that create such a huge total surface area · Splitting the same space into millions of tiny alveoli creates far more surface area than a few big sacs would.
It would be harder to lower the pressure inside the chest enough for a full breath · Without the ribs moving out, the chest can't expand as much, so the pressure drop that pulls air in is smaller.