Week 11 - Healthy Human Body Systems

1 Respiratory System

Lesson 9

Science in Action 8

Read pages 132-134

ScienceFocus 8

Pages 126-153

Lesson 9: Respiratory System

Welcome to the exciting biological world of your own body. Countless lifetimes of study can now bring you an understanding of how it functions.

One of the most important ideas to remember is that, although we study organ systems separately, they must all work together to function properly. But its very difficult to discuss how body systems work without using a common vocabulary. So if you learn the names of the parts of the body we will discussing below you will find it much easier.
Background Information

The purpose of the respiratory system is ensure that an adequate level of oxygen is maintained in the blood stream and that the waste product 'carbon dioxide' is removed from the body.

Think of the respiration system as a upside down tree. The further you go along the system the smaller the branches get. Look at the diagram below and you will see what I mean.

There are no muscles in the lungs, so what pumps the air in and out. First there are muscles between your ribs that contract and pull your chest up and out. Try it! Put your hand on your chest and take a deep breath in. What direction did your hand go?

Along with your rib muscles, there is a very large muscle below your ribs called the diaphragm muscle. As it contracts it pulls downward. The combination of these two muscle actions creates a vacuum in your lungs and air rushes in. When all these muscles relax the lung volume is reduced and air is forced out.

In the diagram below, we can clearly see the upside down tree design. When you breath in air rushes down the trachea (trake ea) and then divides into the left and right bronchi (the the plural word we use). From there the air is further divided into smaller and smaller bronchioles until it finally arrives at little sacs called alveoli .

Here in the alveola , the oxygen enters the blood stream while the excess carbon dioxide leaves the blood and is exhaled from the lungs. This process is called gas exchange .

  Exercise 3.1: Breathing Rate
Make sure you have read Read pages 417- 419

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