How Do Our Lungs Work?

We breathe by drawing air into our lungs (inhaling) and letting it out again (exhaling).

Every time we breathe, a fresh supply of air makes contact with the lung with tissue which contains blood. In the lung, blood and air exchange some of the gases they contain.

The lungs fill both sides of the chest. The lung tissue is like a sponge in some ways. The spaces, or air sacs, are pockets where the air is received. The gases which are needed are taken in, and the unwanted gases are forced out. The air sacs are separated from each other by very thin walls filled with very fine blood vessels calles capillaries. Only a few cells separate the blood from the air, so gases can easily through these thin walls.

The lungs are elastic, which means they can strech. When we breathe in, the chest gets bigger and the lungs expand with it. Then airrushes in through the nose, mouth and throat to the air sacs of the lungs. When we breathe out, the space inside the chest becomes smaller. The lungs partly close and the air is forced out again.

How much air can the lungs hold? The lungs of an adult man can probably hold about seven pints of air; those of woman, about five pints.

The lungs are never empty, even when you try hard to force the air out. The amount of air remaining after exhaling with great force is called “residual air”. When we inhale we mix fresh air with this residual air.

Breathing goes on regularly even when we don’t think about it, or when we are asleep. But we can stop breathing for a short time if we want to, as when we hold our breath when we are under water.

1. When we breath in, ……..a the unwanted gases are forced outb air rushes in to the air sacs of the lungsc the nose, mouth and throat closed the air sacs are separated from each other

2. The lungs partly close when …..a blood and air exchange gasesb the air is receivedc the chest becomes biggerd we breath out

3. The lungs of an adult woman can hold about ….a seven pints of airb five pints of airc three pints of bloodd twelve pints of air and blood

4. The lungs are never empty because …..a an amount of air remains in the lungs after exhalingb we cannot force all the air outc fresh air mixes with the remaining aird we never stop breathing in

5. We can stop breathing when…..a the lungs are full of airb the air is forced outc we are asleepd we are under water

6. Capillaries are …….a fine blood vessels in the walls between the air sacsb cells which separate the blood from the airc gases which are taken into the air sacsd lung tissues which are similar to a sponge

7. “….so gases can pass easily through these thin walls”. The underlined phrase refers to ……a the cells in the air sacsb the blood vessels in the lungsc the walls which separate the sacsd the lung tissues

8. “When we breathe in, the chest gets bigger and the lungs expand with it.” The underlined word means……a partly closeb become largerc are elasticd become smaller