To understand how an amino acid chelate is absorbed into the mucosal cell from the lumen, comprehension of the structure of the small intestine is important. If one were to examine its morphology, one would see that the luminal surface tissue, known as the mucosal tissue, is folded into the villi, which extend into the lumen. Depending on the locus in the small intestine, these villi can be continuous folds or, in other areas of the intestine, they become more pronounced and resemble individual ‘nger-like or leaf-shaped projections.1 Each villus greatly increases the effective absorption area of the small intestine as well as the secretory surface of the mucosa. A single layer of mucosal cells, also known as absorptive cells, lines each villus, including the remainder of the mucosal tissue2 (Figure 8.1).