Fill in the blank.
1. Air enters the body through the ___ and the ____.
2. It then enters the ___ which splits into 2 tubes called the _____.
3. Each of the ____ attaches to a ____________
4. In the _______, the _____ divide several times into very small tubes called ___.
5. ______ end in small, thin air sacs called ______.
6. In the _______, _________ from the air we breathed enters in your blood and _________and ______________ from your blood go into the air.

7. Describe how muscles help us breathe.