Absorptive surface area of the small intestine is greatly increased by the presence of

The epithelial cells that make up the small intestine are known as mucosa, and these mucosa have a variety of different layers that give rise to different functions. The mucosa's surface area is increased through villi, which are small circular folds that have finger-like projections. Microvilli are found on the mucosa's cell membrane  and they too are finger-like projections that increase the surface area even further.