GI Digestion and Absorption

  • Life requires ingestion of energy-rich biological molecules, electrolytes, water, and certain vitamins. The gastrointestinal system possesses mechanisms for absorbing all of these substances as discussed in the subsections below. However, because the GI system must retain a tight epithelial barrier to prevent invasion of intestinal microbes, large biological macromolecules must be digested into small molecules before their absorption can occur.