The physiological functions of the gastrointestinal system involve digestion and fermentation, absorption and excretion, and motility. Each function is associated with one or a few gastrointestinal organs (Table 2.1).
Digestion is a complex process. It includes masticating, mixing, and triturating the food to disrupt the matrix followed by solubilization of the components and micelle formation with the nonsoluble products (especially fats), and, finally, partial or complete hydrolysis of the complex food molecules (peptides and proteins, lipids, some complex carbohydrates, and nucleic acids).
Strictly speaking, digestion comprises only the final hydrolytic step aimed at decomposing (Figure 2.2):
FIGURE 2.1 Schematic representation of the gastrointestinal system.
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