Cilium

A cilium (Latin for eyelash; the plural is cilia) is an organelle found in eukaryotic cells. Cilia are thick protuberances that project from the much larger cell body.

There are two types of cilia: motile cilia and nonmotile, or primary cilia, which typically serve as sensory organelles. In eukaryotes, motile cilia and flagella together make up a group of organelles known as undulipodia. Eukaryotic cilia are structurally identical to eukaryotic flagella, although distinctions are sometimes made according to function and/or length. Biologists have various ideas about how the various flagella may have evolved.

Types and distribution

Cilia can be divided into primary and motile forms.

Motile cilia

Larger eukaryotes, such as mammals, have motile cilia as well. Motile cilia are usually present on a cell's surface in large numbers and beat in coordinated waves.

Cilia (entomology)

Cilia (Latin for eyelashes; the singular is cilium) in entomology are fine hairs along the edges of the insect wing.

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