Lesson #8: Gas Exchange

Objective:- lungs are structured to optimize gas exchange- smoking damages the lungs and reduces oxygen needed for

respiration

1.2b Balloons full of air?Lungs are like balloons made of cells

Blood and air mix in the lungs

Lungs are bright red because they are full of blood

Are they right?

1.2b Balloons full of air?

Similarities Differences

1.2b Balloons full of air?

Similarities Differences

Both full of air

Both red

2 lungs share one entrance

Real lungs have blood inside them

Real lungs have tubes running through them

1.2b Balloons full of air?

Blood

Air

Walls of cells separate your blood from the air

1.2b Balloons full of air?The blood and air swap, or exchange, molecules so this is a gas exchange.

carbon dioxide

oxygen

1.2b Balloons full of air?

How could you get more gas exchange?

Gases are only exchanged at surfaces. Blood spends less than a second near an air space when it visits the lungs, so diffusion has to be fast.

1.2b AlveoliWhen an air space is divided there is a greater surface area.

Each cm3 of lung tissue is divided into 170,000 air pockets called alveoli.

How can air get to every pocket?

1.2b Alveoli

1 cm3

Millions of tiny branches lead air to the alveoli.

Thin-walled blood vessels cover the alveoli and gases move in and out of your blood quickly by diffusion.

1.2b Alveoli

lowoxygen

highoxygen

Alveoli spread 1/3 of a mug of blood over a surface area the size of a tennis court...

...so gases are diffused to and from a very thin layer of blood.

1.2b Alveoli

Normal lungs are pink and spongy but smokers’ lungs are tough and black with tar.

How will that affect gas exchange?

1.2b Model lungsWhat happens to your lungs if you smoke?

Out of breathMaria uses an oxygen mask to keep her alive. She can’t get enough oxygen from ordinary air. Her lungs have been damaged by cigarettes.

Maria’s condition is called emphysema. The chemicals in cigarette smoke damage the alveoli walls. Many break down completely so they can no longer be used for gas exchange. The damaged alveoli fill with fluid and make breathing difficult.

1. Make a poster to warn other smokers what breathing problems they should expect when they are older.2. First explain how alveoli speed up gas exchange in normal lungs.3. Then explain what is different about smokers’ lungs.

Make a poster!

Words to use

alveoli diffusion thin cells good blood supply large surface area gas exchange