In Journey into the Cell, we looked at the structure of the two major types of cells: prokaryotic and eukaryotic cells.

Now we turn our attention to the "movers" of a eukaryotic cell, cilia and flagella.

Cilia and flagella are protrusions from some cells that aid in cellular locomotion. They are formed from specialized groupings of microtubules called basal bodies.
If the protrusions are short and numerous they are termed cilia. If they are longer and less numerous (usually only one or two) they are termed flagella.

Typically cilia and flagella have a core composed of microtubules connected to the plasma membrane arranged in what is known as a 9 + 2 pattern.

The pattern is so named because a ring of nine microtubule "doubles" has in its center two singular microtubules.

This organization allows the sliding of the microtubule doubles against one another to "bend" the cilia or flagella. This type of organization is found in most eukaryotic cilia and flagella.

Both cilia and flagella are found in numerous types of cells. For instance, the sperm of many animals, algae, and even ferns have flagella.

Cilia can be found in areas such as the respiratory and female reproductive tracts.