Final answer:
Microtubules make up the mitotic spindle and are organized by the centrosome during cell division, whereas intermediate filaments provide structural support but are not part of the spindle.
Step-by-step explanation:
The cytoskeletal structures that make up the mitotic spindle are the microtubules. Microtubules are the thickest of the cytoskeleton structures, and they radiate outwards from an area near the nucleus called the centrosome, which is the microtubule-organizing center.
During cell division, they form the mitotic spindle, which is critical for the separation of chromosomes into two new cells. While intermediate filaments provide structural support and resist tension, they are not directly involved in the formation of the mitotic spindle.