What does "villus" describe?

"Villus" refers to filamentous processes found on membranous surfaces, particularly in the intestines. These tiny, finger-like projections serve to increase the surface area for absorption of nutrients. The structure and function of villi are crucial in enhancing the efficiency of nutrient absorption during the digestive process.

The other options do not accurately define a "villus." Small sac-like structures are more characteristic of other anatomical features, while rounded elevations with itching typically refer to skin conditions or lesions. Additionally, a type of internal organ does not align with the definition of a villus, as it specifically describes a cellular or tissue structure related to absorption rather than an organ itself.