Cytoskeleton

Cell cytoskeleton is made up of these 3:

• Actin microfilaments: length ~7 nm, twisted, inextensible
• Microtubules: ~24 nm, hole along the axis, not twisted
• Intermediate filaments: 10-12 nm, parallel bundles of filaments, not tubular; could be twisted in long pitch, but not in short pitch

http://en.wikipedia.org/wiki/Vimentin