What Are Ciliated Cells?

A ciliated Paramecium cell.
Two paramecia with cilia extending from their membranes.
Paramecium caudatum are single-celled, ciliated organisms.
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  • Written By: Kendra Young
  • Edited By: Jenn Walker
  • Last Modified Date: 21 March 2014
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Ciliated cells are cells covered in tiny hair-like projections known as cilia. The word "cilia" is derived from the Latin term for "eyelash," which is what they look like. Cilia work by moving back and forth in unison, allowing the cell to move through liquid or mucus environments or to propel objects, such as food, dust, or bacteria, around themselves.

Single-celled organisms and some epithelial cells found in many types of animal tissues often have cilia attached to them. Ciliated epithelial cells are rarely found in plants. One possible evolutionary explanation for this might have to do with the loss of moisture. Cilia dramatically increase the surface area of a cell, increasing the chance for evaporation and the need for water. Cycads, a type of tropical tree, are one of the few plant genera that possess ciliated cells.

In animals, ciliated epithelial cells are found in many parts of the body. The brain, for example, uses these cells to help circulate cerebrospinal fluids through the brain and spinal column. Research conducted in 2007 by Victor Chizhikov, Ph.D., and Kathleen Millen, Ph.D., showed that they are vital for normal brain development in the cerebellum as well.


Ciliated cells are also used in the oviducts to move the ova to the uterus and in the respiratory system to eliminate dust and germs from nasal passages. Those in the respiratory system are the primary cells affected by respiratory viruses, such as the cold or flu. These viruses work by killing the cell completely or by paralyzing the cilia. This causes mucus and bacteria to accumulate, leading to such secondary infections as sinusitis or bronchitis.

When referring to single-celled organisms, those with cilia make up a very important group of protists, with thousands of documented species. These protists are considered the most complex single-celled organisms known and are very important to aquatic environments. Protists vary in their ability to tolerate pollution and are often used as an indicator species to quickly measure the health of a body of water.

Cilia are made of microtubules, which are thick spirals of tubulin, and are covered by the cell membrane. They are often confused with flagella due to the numerous similarities, but there are key differences between the two. The main difference is in regard to the number of projections: cilia refer to multiple projections from a single cell whereas flagella refer to a single projection from one cell. The whip-like tails of sperm and giardia cells are excellent and easily recognizable examples of flagellate cells.


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Post 8
I didn't know that Cycad trees has ciliated cells! They are very interesting to look at. The trunks look like rough, fancy columns, and the green tops look like ferns suddenly bursting out of a vase.

Since ciliated cells require lots of water, it makes since that Cycad trees live in the tropics. It's very humid down there, and the trees probably get rain about once a day!

Post 7

I didn't know that a virus could actually interrupt a ciliated cell's function! I really didn't know exactly what caused all that congestion, but if the ciliated cells are either dead or paralyzed, I understand how mucus could build up.

It builds up quickly, too. If I have a cold, my nose runs so much that if I plug my nostrils with a tissue, it becomes saturated after just fifteen minutes! I've actually done this before because I got tired of wiping my nose every few minutes.

Having a bunch of paralyzed ciliated cells really messes up the way things work. I am miserable for a week or two when I have a cold, and most of this misery is due to congestion in my nose.

Post 6
For years, I thought that the cilia on cells in the nose were the nose hairs you could actually see. I finally learned that cilia are microscopic and are located further back in the nose.

The nose hairs we can see trap dust and particles before they get very far. The cilia work on moving the mucus and things that get past the nose hairs.

Post 5

I was helping my daughter with her biology homework the other day, and I saw a diagram of a ciliated cell. The cilia looked like fringe along the outer edge of the cell. There must have been thousands of them!

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