Science 8th grade
UNIT 4: Respiration 4.1 The human respiratory system
Science 8th grade
UNIT 4: Respiration 4.1 The human respiratory system
Every cell in your body needs a supply of oxygen. The cells use the oxygen for respiration. They produce carbon dioxide as a waste product.
The oxygen comes from the air around you. About $20\% $ of the air is oxygen.
The carbon dioxide that your cells produce goes back into the air around you.
About 0.04% of the air is carbon dioxide.
The organs that help to get oxygen from the air into your blood, and to get rid of carbon dioxide, make up the respiratory system.
When you breathe in, air flows through the trachea and then into the two bronchi, which carry it deep inside the lungs. When you breathe out, air flows back in the opposite direction.
Inside the lungs, oxygen passes from the air into the blood, and carbon dioxide passes out of the blood into the air. This is called gas exchange. You will find out more about this in the next topic.
The structure of the human respiratory system.
Question
1) Write a sentence to describe the function of each of these parts of the human respiratory system.
a: trachea
b: bronchus
Activity 4.1 (Measuring the volume of air you can push out of your lungs)
1) You need a large, plastic bottle - preferably one that can hold at least $3dm$ ($3litres$) of water. First, you need to mark a scale on the bottle to show the water level when it holds different volumes. In your group, discuss how you can do this. Then mark the scale carefully on the bottle. Your scale should go all the way to the top of the bottle.
2) Fill the bottle right to the very top with water. Put the lid on.
3) Put water into a large bowl until it is about half full. Turn the bottle upside down, and stand it in the water in the bowl. Carefully remove the top. All the water that you put into the bottle should stay inside it. (If it doesn't, start again!)
4) Slide a piece of tubing into the bottle. Take a deep breath in, then breathe out as much air as you can through the tubing. Your exhaled air will go into the bottle and push out some water.
5) Use the scale on the bottle to find the volume of air you breathed out.
6) If you have time, repeat steps 2 to 5 two more times. Use your three results to calculate a mean value for the volume of air you can push out of your lungs.
