Clinical Nutrition in Gastrointestinal Disease

Alan Buchman, MD, MSPH

Chapter 8: Macronutrient Digestion, Absorption, And Metabolism (continued)

Brian M. Chung, PhD; Kelly A. Tappenden, PhD, RD

The absorptive epithelium of the gastrointestinal (GI) tract serves the dual purpose of providing a barrier that impedes the free passage of ingested toxins and pathogens to the systemic circulation, while digesting and subsequently absorbing ingested nutrients required for the continuation of life. The primary site of macronutrient absorption is the small intestine. The morphology of the small intestine is characterized by a series of folds serving to progressively increase absorptive area over that of a smooth tube. Plica muscularis, which are button-like projections of the epithelium into…