Cilia are hair-like structures that project from the surface of some cells. They are much smaller than flagella (another type of cellular projection) and beat in a coordinated, wave-like motion.
Here are some examples of how cilia function:
* Movement: In some single-celled organisms, cilia help with movement through fluids.
* Filtering: In the respiratory system, cilia line the airways and help to sweep mucus and debris out of the lungs.
* Sensory perception: Cilia in the inner ear are involved in hearing.
While flagella are also involved in movement, they are longer and typically move in a whip-like fashion.
