Cilia  and flagella  are hair-like, microscopic, filamentous protoplasmic processes. Both cilia and flagella are involved in cell motility. 

Paramecium and Bacterial flagella

The body of a Paramecium (unicellular protozoan) is fully covered by a few thousands of cilia. Cells present in the upper respiratory tract of mammals’ bear cilia to expel particulate matter present in inhaled air. A mammalian spermatozoan contains single flagellum, while a unicellular Chlamydomonas, a green alga has two flagella. Even a prokaryotic bacterium has flagella but it differs structurally from a eukaryotic flagella. 

 Although cilia and flagella are morphologically and physiologically identical, but it can be differentiated on the basis of their size, number and function.

Cilia (Singular: cilium)

Flagella (Singular: flagellum)

Smaller in size up to 5–10 μm

Larger in size up to 150 μm

Occurs throughout the surface of a cell

Occurs at one end of the cell

Numerous in number

One or two in number

Moves in a co-ordinated rhythm and show sweeping or perpendicular stroke motion

Moves independently and show undulatory movement or whiplash movement

It is found in:

• Protozoans (class—Ciliata)

• Ciliated epithelium of metazoan

• Larvae of Platyhelminthes, ribbon worms, Annelids, Mollusca and Echinodermata

It is found in:

• Plants (algae and gamete cells)

• Sponges (Choanocyte cells)

• Spermatozoa of Metazoa

• Protozoans (class—Flagellata)

Cilia are smaller in size and present in large number in a ciliated cell whereas, flagella are longer in size and typically vary from one or two in number.

Cilia and flagella are fibrillar and made up of microtubules. Their fundamental structure is same. Both arise from a centriole-like structure known as basal body. Electron microscopic view shows that they are bounded by a unit membrane (90 Å thickness ) which is continuous with plasma membrane. They have a core known as axoneme in the matrix containing nine peripheral and two central microtubules. Such an arrangement is referred as 9+2 array. Central fibrils are enclosed by a sheath.

Learn more: Functions of Cilia and Flagella

Post a Comment

We Love to hear from U :) Leave us a Comment to improve this site
Thanks for Visiting.....

Previous Post Next Post