The Cytoskeleton appears as a maze-like network of hollow fibers, extending the organelles in a kind of three-dimentional web.

Microtubules are made up of common protein called tubulin. Each tubulin molecule consists of two globular protein parts (x, B tubulin). In the microtubule these protein "diamers" are arranged to form a hollow tube (in cross section). Microtubules, along with the cytoskeleton helps maintain the cells shape. Microtubules are important parts of the "centrioles", "cilia" and "flagella".

Centrioles and Basal Bodies

Centrioles are small "clusters" of microtubules arranged in a tubular bundle.

Cilia and Flagella

These are fine hair-like, movable projections extending from the surface of some cells. In both cases the plasma membrane protrudes outwards covering the inner structures. Structurally, the cilia and flagella are almost identical to one another they differ only in their length, numbers per cell and proteins of motion.

Cilia: are short, numerous and more in a characteristic "rowing" pattern. All eukaryotic cilia are the same.

Flagella: are more variable, but they are always, long, fewer in number and move by undulation (in waves).

Both cilia and flagella serve to move the cell through the environment or move fluid (of the environment) past the surface of the cell.

In a cross-section a cilium or a flagellum is seen to consist of a regular array of microtubules. Two tubules run down the centre of the shaft and nine pairs of microtubules surround the central two these called "nine-plus-two".

The pairs of microtubules are connected by short arms of protein Dymein and movement of the cilia or flagella is the result of sliding movements between microtubule pairs.

Beneath each cilium of flagellum in the cytoplasm of the cell is a basal body. The two central microtubules of the cilia/flagellum do not extend into the basal boy, the nine pairs of microtubule do and they are joined by a third microtubule. Therefore basal bodies have some structure as centriols. Indeed it is believed that centrioles are needed to create basal bodies in order to produce cilia and/or flagella.

Eg. Chlamydomonas sp. has two flagella, during mitosis they are absorbed into the cell the two basal bodies migrate to the region of the nucleus and organize the spindle then following mitosis (and their own replication) the centrioles again become basal bodies and the flagella reappear.