The primary functional difference between microvilli and cilia in eukaryotic tissues is that microvilli increase surface area, while cilia facilitate movement.
Microvilli: Surface Area Amplifiers
Microvilli are small, finger-like projections of the cell membrane that greatly increase a cell's surface area. This expanded surface is essential for efficient absorption and secretion.
- Key Function: To maximize the interaction between the cell and its environment, particularly for nutrient absorption or waste secretion.
- Location: Commonly found in the lining of the small intestine, where they absorb nutrients, and in kidney tubules, where they facilitate reabsorption.
- Structure: Membrane protrusions, which do not move themselves.
Cilia: Cellular Movement Facilitators
Cilia are hair-like structures that project from the cell surface and are capable of movement.
- Key Function: To move substances across the cell's surface or to move the entire cell.
- Types: They can be categorized into motile cilia, which beat in a coordinated fashion to generate fluid flow, and non-motile (primary) cilia, which act as sensory organs.
- Location: Motile cilia are found in the respiratory tract to move mucus, and in the female reproductive system to move eggs; and motile cilia also enable movement of single-cell eukaryotic organisms.
Summary: Microvilli vs. Cilia
| Feature | Microvilli | Cilia |
|---|---|---|
| Primary Function | Increase surface area for absorption and secretion | Facilitate movement of substances or cells |
| Movement | Non-motile; fixed projections | Motile (can move); hair-like structure |
| Structure | Membrane protrusions | Hair-like projections, containing microtubules |
| Example Locations | Small intestine, kidney tubules | Respiratory tract, fallopian tubes, single-celled eukaryotes |
As highlighted in the provided reference, "Microvilli are cellular membrane protrusions that increase the surface area of eukaryotic cells. Cilia are used to move cells throughout certain parts of the organism mostly animals and a few plants." This statement clearly distinguishes their roles, with microvilli enhancing absorption/secretion via surface area increase and cilia enabling movement.
