Do cilia and microvilli contain a similar number of parallel actin filaments?

Cilia and microvilli have different structures and functions, leading to distinctions in their composition, particularly regarding the number of parallel actin filaments they contain. Microvilli, which are small, finger-like extensions of the plasma membrane, are supported by a core of actin filaments. They typically contain a bundle of approximately 20-30 actin filaments arranged in a parallel configuration, which helps increase the surface area of cells, particularly in the intestines for absorption.

In contrast, cilia are larger and more complex hair-like structures that primarily function in movement, such as propelling fluids over cell surfaces. Cilia have a different internal structure known as the "9+2" arrangement, which consists of nine outer microtubules surrounding two central microtubules. While there are associated proteins and some actin filaments involved in ciliary function, the predominant structural component is microtubules, not actin filaments. Therefore, cilia do not contain a similar number of parallel actin filaments as microvilli.

This distinction clarifies why the statement is false; microvilli are characterized by their parallel actin filaments, while cilia are primarily composed of microtubules, leading to