Point of Departure The mechanical breakdown of food begins in the mouth, where food is ingested, chewed, and swallowed. Automatic Transport The esophagus is a short, muscular tube in which involuntary, wavelike contractions and relaxations propel food from the mouth to the stomach. Storage and Processing The stomach acts as a temporary storage and processing facility before emptying its contents into the small intestine. Early stages of digestion take place in the stomach where pepsin and lipase aid in digesting protein and fat. Treatment Facilities In the small intestine, enzymes break down large, complex food molecules into simpler units that can be absorbed into the bloodstream. The pancreas is an organ that does double duty, secreting digestive enzymes into the gut and hormones, including insulin and glucogon, into the blood. Important for fat metabolism, the liver produces bile and partially stores it in the gall bladder between meals. End of the Line The primary function of the large intestine is to absorb electrolytes and water. Also, this is where microbes ferment nutrients that have so far escaped digestion and absorption.
COMMITTEE ON NUTRIENT REQUIREMENTS OF DOGS AND CATS DONALD C. BEITZ, Chair, Iowa State University JOHN E. BAUER, Texas A&M University KEITH C. BEHNKE, Kansas State University DAVID A. DZANIS, Dzanis Consulting & Collaborations GEORGE C. FAHEY, University Of Illinois RICHARD C. HILL, University Of Florida FRANCIS A. KALLFELZ, Cornell University ELLEN KIENZLE, Zentrum Für Lebensmittel Und Tierernährung, Oberschleissheim, Germany JAMES G. MORRIS, University Of California, Davis QUINTON R. ROGERS, University Of California, Davis Support for this pamphlet was provided by the President’s Circle Communications Initiative of the National Academies. The pamphlet was written by Dale Feuer based on a report by the Committee on Nutrient Requirements of Dogs and Cats. Illustration and design by Van Nguyen. Copies of Nutrient Requirements of Dogs and Cats are available from the National Academies Press, 500 Fifth Street, N.W., Washington, DC 20001; 800-624-6242 or 202-334-3313 (in the Washington area); http://www.nap.edu. Copyright 2006 by the National Academy of Sciences. All rights reserved.