Cell center and centrioles

The centrosome, also called the cytocenter, is an amorphous region adjacent to the nucleus, so located in the centre of the cell. It is composed of 2 centrioles.

A centriole is composed of 9 microtubule triplets, that is 27 microtubules in total, with a diameter of about 0.2 μm. Centriolar satellites are non-membranous granules around the centrosome.

The centrosome is the microtubule organizing centre, the MTOC: where most microtubules are formed and their direction and orientation organised. In mitosis it forms the mitotic spindle, and it duplicates itself so that each centrosome has two pairs of centrioles.

Centrioles also form cilia, flagella and basal bodies.

The centrosome, also called the cytocenter, is:

• an amorphous region adjacent to the nucleus, and so located in the centre of the cell;
• composed of 2 centrioles.

A centriole is:

• composed of 9 microtubule triplets, which is 27 microtubules in total;
• about 0.2 μm, that is 200 nm, in diameter.

Centriolar satellites are non-membranous granules around the centrosome.

The 9 × 3 arrangement is the same one met in the basal body of a cilium, and that is not a coincidence: the basal body is a centriole doing a different job.

The centrosome is considered to be the microtubule organizing centre, the MTOC.

It is where most microtubules are formed and where their direction and orientation are organized.

The MTOC is important in mitosis, for the formation of the mitotic spindle.

During mitosis the MTOC, the centrosome, duplicates itself, so that each centrosome has two pairs of centrioles.

The centriole has a role in the generation of the cell's cytoskeleton:

• the formation of cilia and flagella, and of basal bodies.

Basal bodies are a protein structure found in the base of cilia and flagella.