Most digested molecules of food, as well as water and minerals from the diet, are absorbed from the cavity of the upper small intestine.

The mucosa of the small intestine contains many folds that are covered with tiny fingerlike projections called villi. In turn, the villi are covered with microscopic projections called microvilli. These structures create a vast surface area through which nutrients can be absorbed.

Most absorbed materials cross the mucosa into the blood and are carried off in the bloodstream to other parts of the body for storage or further chemical change. This part of the process varies with different types of nutrients.