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What the heck are cilia and flagella and how did they get into my science class?

Lung trachea epithelium with cilia projecting from it
Lung trachea epithelium with cilia projecting from it
Scanning electron microscope image of lung trachea epithelium. There are both ciliated and non-ciliated cells in this epithelium.

Cilia and flagella are projections from the cell. They look like tiny hairs.  They are made up of microtubules. They are designed either to move the cell itself or to move substances over or around the cell.   In this regard, they are a lot like the legs and arms of humans.

The primary purpose of cilia in mammalian cells is to move fluid, mucous, or cells over their surface. Cilia and flagella have the same internal structure. The major difference is in their length.

Below is a list of the major differences between cilia and flagella.

Cilia

  • Short, hair-like structures that typically cover the entire cell surface.
  • Found in large numbers on the surface of certain types of cells, such as those that line the respiratory tract.
  • Move in a coordinated back-and-forth motion, like oars on a boat.
  • Used for moving fluids and particles across the cell surface.

Flagella

  • Longer hair-like structures that are typically found singly or in small numbers.
  • Commonly found on cells that move, such as sperm cells.
  • Move in a whip-like motion to propel the cell forward.
  • Used for locomotion.

Image Credits

In-Article Image Credits

Chlamydomonas, a single-celled green alga with flagella projecting from it via Wikimedia Commons by Dartmouth College with usage type - Public Domain
Lung trachea epithelium with cilia projecting from it via Wikimedia Commons by Charles Daghlian with usage type - Public Domain. Via Dartmouth

Featured Image Credit

Lung trachea epithelium with cilia projecting from it via Wikimedia Commons by Charles Daghlian with usage type - Public Domain. Via Dartmouth