What are the inner walls of the small intestine lined with?

The inner walls of the small intestine are lined with villi and microvilli. Villi are tiny, finger-like projections that increase the surface area of the intestinal lining, allowing for more efficient absorption of nutrients as they pass through the intestines. Each villus is covered with microvilli, which are even smaller projections that further enhance this surface area.

This structure plays a critical role in digestion and nutrient absorption, ensuring that the body can effectively utilize the nutrients from the food we eat. The increased surface area afforded by the villi and microvilli creates a more efficient environment for nutrient transfer into the bloodstream.

In contrast, other options do not accurately describe the lining of the small intestine. While epithelial cells are present and play a role in forming the lining, they do not encompass the specific structural features of villi and microvilli that are essential for nutrient absorption. The terms microflora refer to the bacteria in the gut rather than the physical structure of the intestinal lining. Gastric folds and tissues relate more to the stomach and not the small intestine. Thus, the choice that accurately reflects the specialized structure of the small intestine's inner walls is one that highlights villi and microvilli.