The respiratory system

What do our muscles need to function?

At the end of the small tubes there are small air sacs called.......................

Trachea is connected to the

The_________is a muscle that contracts when you breathe in to help the lungs expand.

There are lots of small air tubes inside the lungs called............

The respiratory system takes in oxygen and expels.............

Air flows down the________________into the lungs.

Where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out are called.................

What does the respiratory system takes in?

The trachea divides into two..........................