How does the structure of villi allow efficient absorption in the small intestine?
By increasing the surface area and by being made up of a single layer of cells both of which enhance absorption.
The surface of the small intestine is extensively folded into villi and microvilli that increase the surface area of the small intestine.
Every square inch of the intestinal mucosa is comprised of around 20,000 villi, and the surface cells of the mucosa also have projections of their cell membranes called microvilli, all of which contribute to the increased surface area.
This enables a great area to be available for the absorption of nutrients.
In addition, the villi and microvilli are only a single cell-layer thick and have an extensive network of blood capillaries behind them to distribute the absorbed nutrients.