MicrofilamentsThe thinnest fibers, about 7 nm across. Made of two twisted strands of actin. They form a mesh under the membrane and help the cell move and change shape.
Intermediate filamentsRope-like fibers of several twisted strands. Thicker than microfilaments and thinner than microtubules. They bear tension and hold the nucleus and other parts in place. Keratin is one kind.
MicrotubulesThe widest fibers: hollow tubes of the protein tubulin. They hold the cell's shape and act as tracks for moving things round the cell.
CentrosomeThe region near the nucleus where microtubules start from, in animal cells.
CentriolesTwo small cylinders of microtubules inside the centrosome. They sit at right angles to each other.
Motor proteinA protein that walks along a microtubule. It uses energy from ATP and carries a load such as a vesicle.
How this list was compiled: Read 2026-09-27. (1) OpenStax Biology 2e, 4.5 The Cytoskeleton, https://openstax.org/books/biology-2e/pages/4-5-the-cytoskeleton (used to check, nothing copied): three types of fibers, microfilaments, intermediate filaments and microtubules; microfilaments about 7 nm across, two intertwined strands of actin, a track for the motor protein myosin; intermediate filaments of several strands, bearing tension, keratin among them; microtubules of alpha- and beta-tubulin, the structural elements of centrioles, the centrosome's two perpendicular bodies. (2) Wikipedia, Cytoskeleton, https://en.wikipedia.org/wiki/Cytoskeleton : actin filaments (microfilaments), intermediate filaments and microtubules; the centrosome as the main microtubule organizing center of animal cells, with a pair of centrioles; motor proteins such as kinesin and dynein moving along microtubules and myosin along actin. Licence: own work
The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work
How it works
A cytoskeleton diagram labeled: the network of protein fibers inside an animal cell, drawn in the cell and then each kind of fiber magnified below. Tap a fiber in the cell and its magnified form lights too.
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The three fibers
Microfilaments are the thinnest, two twisted strands of actin, making a mesh under the membrane. Intermediate filaments are rope-like and bear tension. Microtubules are the widest, hollow tubes of tubulin that hold the cell's shape.
Centrosome and motors
In animal cells the microtubules spread out from the centrosome by the nucleus, which holds a pair of centrioles at right angles. Motor proteins walk along the microtubules, carrying vesicles round the cell. Myosin, a motor protein too, pulls along microfilaments when muscles contract.
Thinnest to widest: microfilaments, then intermediate filaments, then microtubules.
Questions and answers
What are the three parts of the cytoskeleton?
Microfilaments made of actin, intermediate filaments, and microtubules made of tubulin, from the thinnest to the widest.
What does the cytoskeleton do?
It gives the cell its shape and holds its parts in place, lets it move and change shape, and serves as tracks for carrying things round the cell.
What is the difference between a centrosome and a centriole?
The centrosome is the region near the nucleus that microtubules grow from. It holds two centrioles, small cylinders of microtubules at right angles to each other.