Respiratory Cilia: Definition & Function

Instructor: Bridgett Payseur

Bridgett has a PhD in microbiology and immunology and teaches college biology.

Cilia are short fibers on the outside of a cell that usually move the cell in its environment. Respiratory cilia differs in that it doesn't move the cell, but helps keep your lungs healthy by trapping and removing dirt, dust, and germs you inhale.


If cells could grow beards, they would look like cilia (singular: cilium). Cilia are short, hair-like strands covering the outside of a cell. They're not actually hair though, they are stands made of proteins. Cilia help cells move around. They beat back and forth, like oars on a rowboat to propel the cell through its environment. Cilia are generally regulated so that they beat in unison, just as if they had someone calling out 'stroke!' to keep them in time.

The Respiratory Tract

The respiratory tract allows you to breathe. You take in oxygen to power the cells in your body, and expel carbon dioxide and water as waste products. Your respiratory tract begins with your nose and mouth. The oxygen then moves down into your trachea, a tube connecting your mouth to your lungs. The trachea branches off into two bronchi (singular: bronchus), one for each lung. The bronchi then branch into even smaller bronchioles, to reach all throughout the lungs. This is very similar to the way a tree branches out, but instead of leaves the bronchioles end in small sacs called alveoli (singular: alveolus). Oxygen and carbon dioxide are exchanged in the alveoli.

Respiratory Cilia

The cells lining your respiratory tract don't move around. Why, then, would they need cilia? It needs cilia because your respiratory tract is very vulnerable to invasion. Every time you inhale, you take in more than just oxygen. The air you breathe is full of contaminants- pet hair, pollen, dust, bacteria, viruses, fungi. Your body needs a way to get rid of all that stuff, otherwise you can get sick.

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