Digestion, Absorption and Metabolism Presented by Janice Hermann, PhD, RD/LD OCES Adult and Older Adult Nutrition Specialist

What Is Digestion Process whereby the body breaks down food into absorbable nutrients. Digestive tract is a long tube surrounded by muscles. The muscles alternate contracting and relaxing pushing food along.

Mouth Teeth grind food to reduce the size. Saliva released to help moisten food. Some carbohydrate digestion begins. Tongue pushes food to the back of the mouth to start swallowing reflex. Food passes through the esophagus and enters stomach.

Stomach Distended pouch. Strong circular muscles at each end control food entering and leaving. Mixes food by muscular contractions causing food to break up further. Secretes hydrochloric acid: Begins protein digestion. Kills microorganisms in food. Nutrients not absorbed except water and alcohol.

Small Intestine Most digestion and absorption occurs in small intestine. Bile released to emulsify (break up) fat. Pancreatic enzymes released to digest carbohydrates, proteins and fats. Final digestive enzymes in intestinal lining break down carbohydrates, proteins and fats into absorbable units.

Final Digestion Products Final digestion products absorbed by cells lining small intestine. Carbohydrates: Monosaccharides Proteins: Amino acids Chains of 2 or 3 amino acids Fats: Fatty acids Glycerol Monoglycerides Vitamins, minerals, water and some larger fat-like compounds such as cholesterol are not broken down before they are absorbed.

Absorption Water-soluble nutrients and short fatty acids released directly into the bloodstream. Longer fatty acids, fat-soluble vitamins, and fat-like compounds such as cholesterol are not water-soluble. Triglycerides reform in intestinal wall. Packaged into a chylomicron and released into lymphatic system.

Indigestible Matter After digestion and absorption of nutrients, indigestible matter, such as fiber moves into the large intestine. Indigestible matter is compacted by removing water. Little nutrient absorption occurs in large intestine.

Metabolism Chemical reactions that occur in the body: Building and maintaining body tissues Regulating body functions Supplying energy For metabolism to occur the body needs: Water Energy Oxygen Nutrients