- The cytoskeleton is a complex network of protein filaments that provides structural support, maintains cell shape, and facilitates intracellular transport, cell division, and motility.
- The three main structural components of the cytoskeleton are:

1. Microtubules – These are hollow tubes made of tubulin proteins. They play a crucial role in maintaining cell shape, enabling intracellular transport (such as movement of organelles), and forming the mitotic spindle during cell division.

2. Microfilaments – Also known as actin filaments, these are thin filaments primarily composed of actin. They are involved in generating cellular movements, maintaining cell shape, and enabling processes such as cytokinesis and cell migration.

3. Intermediate filaments – These filaments provide mechanical strength to cells. Unlike microtubules and microfilaments, intermediate filaments are more stable and help resist mechanical stress. Examples include keratins, vimentin, and neurofilaments.

It is important to distinguish these cytoskeletal components from extracellular fibers such as collagen, elastic, and reticular fibers, which are part of the extracellular matrix and not the cytoskeleton itself.

Also, while myosin is an important motor protein associated with microfilaments, it is not a structural element of the cytoskeleton. Similarly, neurofilaments, desmin, and keratin are types of intermediate filaments but do not alone represent the entire cytoskeleton.

Therefore, the correct answer is Option 1: Microtubules, microfilaments, intermediate filaments.

Reference: Abbott's Cell Biology, 5th Edition, Chapter 4 – The Cytoskeleton / Page 112-120