Final answer:
Microtubules, composed of alpha and beta-tubulin, form the mitotic spindle during cell division, and are distinct from actin-made microfilaments and keratin-related intermediate filaments.
Step-by-step explanation:
The cytoskeletal structures that make up the mitotic spindle are microtubules. These are the thickest elements of the cytoskeleton and are composed of alpha and beta-tubulin polymers, which form hollow cylindrical structures necessary for various cellular functions. Microtubules are vital for maintaining a cell's shape, enabling the movement of organelles within the cell, and playing a crucial role in cell motility, particularly in the formation of mitotic spindles during cell division. In contrast, microfilaments, which consist of actin, and intermediate filaments, often made up of proteins like keratin, serve other structural and motility functions within the cell. Therefore, the correct answer to the question is that microtubules compose the mitotic spindle.
Microtubules make up the mitotic spindle. They are composed of alpha and beta tubulin protein monomers that form hollow cylinders. Microtubules help the cell keep its shape, hold organelles in place, and form the mitotic spindle during cell division.