Once upon a time there were 2 oxygen molecules. Their names are Jeff and Emma. They float around in the fresh air and wait for someone to inhale them.

This is Bob. Today he decided to go outside for a stroll and enjoy the bright and sunny weather. Bob takes a big breath and enjoys the sunlight and then he asks himself, "How did I do that, how do I breathe?" 

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Jeff and Emma float towards Bob excitedly. They ask bob,

“Can we give you a tour of your own respiratory system?” 

Bob is confused. “What is a respiratory system and how is it used?” he asks Jeff and Emma. 

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Jeff and Emma explain, "A respiratory system is a part of your body that allows you to breathe, sing, talk and laugh. The lungs are the main part of your respiratory system. When you inhale your lungs inflate,when you exhale your lungs deflate."

"That sound interesting, Sure!" Bob exclaims. Bob inhales Jeff and Emma and they begin their journey in the Respiratory system.

After Emma and Jeff were inhaled they traveled through the epiglottis. "Yay! Bob we are in your epiglottis!" Emma screamed.

YAY!

"Emma what is an epiglottis?" Bob asks. "The epiglottis is your throat!" Emma said excitedly.

Jeff and Emma continue their journey, after they went down the epiglottis (the throat) They made it into a windpipe which is called the Trachea.

The trachea is a wide, hollow tube that connects the larynx (or voice box) and is made out of cartilage rings (hard tissue). The trachea looks like a tree. It provides an air flow to and from the lungs for respiration.

The trachea is split in too 2 tree like parts, unfortunately Jeff and Emma got split up and went down different passage ways.

Emma made her way to the Alveoli. She found the Alveoli sacs which looked like raspberries. "These little air sacs exchange oxygen and carbon dioxide molecules to and from the bloodstream!" she explained. The air sacs are surrounded by thin, little veins called capillaries.