Epithelial cells often exhibit specializations that enhance their barrier function. For example:
- Microvilli: These finger-like projections increase the surface area for absorption, particularly in the intestinal lining, thereby facilitating nutrient uptake while maintaining a barrier to pathogens.
- Cilia: Found in the respiratory tract, cilia are hair-like structures that move mucus and trapped particles away from the lungs, providing a defense mechanism against inhaled pathogens.
- Keratinization: In the skin, epithelial cells produce keratin, a tough, protective protein that forms a water-resistant barrier, preventing dehydration and pathogen entry.
