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Villis are present in small intestine not in stomach because stomach doesn't absorb nutrients.
Villi of the small intestine are small finger-like projections on the surface. One villus contains many cells and thereby increase the surface area. This is required because a lot of nutrients have to be absorbed in the small intestine. Lots of cells on a small area makes this process efficient as, stomach collects the food, adds gastric acid and enzymes for digestion of food. The stomach does not absorb any nutrients and therefore does not require a larger surface area.