Chapter 5 How do we

breathe?

By Anibelka Henriquez

Lesson 1 What is breathing?

Breathing is automatic, we don’t tell the body when or how to breathe.

We breathe all the time. Breathing means taking air into the

lungs. It also means giving off air the body has

used.

The lungs have helpers

The ribs protect the lungs and help us breathe.

Another helper is the diaphragm.

Do you remember what is a diaphragm is?

Breathing in Several things happen when we breathe

in. The ribs move up and out. The diaphragm moves downward, away

from the lungs. The space inside the chest becomes

larger. The lungs fill with air and expand. This is called inhaling.

Breathing out Several things happen when we

breathe in. The ribs move down and in. The diaphragm moves upward,

toward the lungs. The space inside the chest

becomes smaller. This is called exhaling.

Science Words diaphragm

a sheet of muscle under the lungs

inhaling taking air in

exhaling letting air out

Model Lungs

Objectives To compare inhale and exhale.

To be able to explain what happens to the diaphragm when we inhale.

To be able to explain what happens to the diaphragm when we exhale.

Materials: You will need large clear-plastic bottle three-way hose connector modeling clay 2 rubber bands Plastic tube 3 small balloons scissors

Step 1 Push the plastic tube into one

opening of the hose. Use modeling clay, if necessary, to make an airtight seal.

Fix the balloons tightly onto the other openings with rubber bands, making sure that the connector and the balloons are airtight.

Step 2 Carefully cut off the bottom 1 in from

the bottle, using the scissors. Make sure the cut edge of the bottle is smooth.

Place the balloons and connector inside. Seal the plastic tube into the neck of the

bottle with the modeling clay to make an airtight fit.

Step 3 Tie a knot in the neck of the third

balloon. Then carefully cut it in half, crossways.

Gently stretch the knotted part of the balloon over the lower end of the bottle, and pull it around the sides.

Make the balloon as taut as you can-like a drum skin. Now hold it by its knot.

Step 4 The lower balloon represents the

diaphragm, the main breathing muscle.

Pull it down, as though you were exhaling. This lowers the air pressure in the bottle. Air from the outside rushes in and makes

the two balloons expand, just like the real lungs in your chest.

Now Answer These

1. Tell what happens to the ribs and diaphragm when we breathe in.

2. Tell what happens to the ribs and diaphragm when we breathe out.