Directions: Express what you have learned in this lesson by completing the sentences below. Use the words in the box to fill in the blanks.

The Respiratory System


Air passes into the nasal cavity, where dust and bacteria filtered out by the sticky __________. The air is drawn down the __________ which is kept open by the rings of ____________. At the top of the trachea is a small flap known as the ___________. When you __________ it closes off the trachea to prevent food going into the _________. At the bottom of the trachea, it divides into two ________. Each _________ subdivides again into a mass of fine braches known as __________. These end in tiny hallow bags with bubl-like pockets called _______in which gases are exchanged. The walls of the alveoli are only has only one __________ thick, and their outer surface is covered by a dense network of ___________. The blood flowing through this Capillaries absorbs __________ which __________ through the alveoli and capillary walls, at the same time releases ________ _______ which diffuses in the opposite direction into the aveoli.​