The Physiology of Digestion, Absorption, and Metabolism in the Human Intestine
This chapter addresses the most significant features of digestion, absorption, and intestinal metabolism. An attempt will be made to describe the capacity of these processes and the limits of adaptation which are possible. Neurological impairment of gastrointestinal function may also be evident in alcohol abusers. Patients with alcoholic cirrhosis have been shown to have longer mouth-to-cecum transit times compared to patients with nonalcoholic cirrhosis or compared to normal subjects. The relationship between load and transit is exemplified by the fact that ingestion of food per se slows transit quite markedly thus increasing contact time between luminal contents and the mucosal surface. The microflora play no direct role in water and electrolyte salvage, but do this indirectly by hydrolyzing and fermenting malabsorbed nutrients to short-chain fatty acids (SCFA) which can be absorbed by the colonic mucosa, accompanied by water and electrolyte uptake. The higher pH of the duodenal contents aids in further emulsification and facilitates the action of pancreatic lipase.