The Function of Cilia

Cilia (singular: cilium) are microscopic, hair-like structures that extend outwardfrom the surface of manyanimal cells. These structures are important in the cell cycle and replication, and cilia play a vital part in human and animal development and in everyday life.

A typical cilium is between one and ten micrometers long, and usually less than one micrometer wide. They are often divided into two different types, and these types can work together or separately. They types are motile and non-motile.

Motile cilia, which means "moving," can be found in the respiratory tract, middle ear, and other body systems. Multiple cilia willwave in a rhythmic or pulsating motion, and use that motion to keep sensitive internal passagewaysfree of mucus or foreign particles, for example. Body cells that have a single moving cilium are sperm cells, which use that cilium to propel the cell.

The non-motile cilia play a crucial role in many different organs. Some serve almost like antenna that receive sensory information for the cell, processing signals from the other cells or the fluids surrounding it. For example, cilia in the kidney are forced to bend as urine flows past, which sends signals to the cells that it is flowing. Non-motile cilia inside the eye are housed in the retina's photoreceptors, allowingimportant molecules to be transported from one end to the other.

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