Cilia are long hair-like projections present on the plasma membrane and made up of microtubules. Cilia can also be found in some specialized cells like sensory cells of ears, which are responsible for the initial sensory input of hearing. The length of each cilium is between 5 to 10um and has a diameter of 0.2 um. Cilia are motile and beat in one direction to move the entangled particles from the surface. If we look at the structure of cilium, it is made up of microtubules arranged in a longitudinal orientation. This orientation is also known as 9+2 orientation which means each cilium has nine microtubule doublets which are located peripherally with two microtubules in the center. The function of motile cilia is to move water relative to cells