Functions of the Digestive System

INGESTION Food placed in mouth Active, voluntary action

PROPULSION Food is propelled from one digestive to the next Peristalsis (involuntary) Alternating waves of contraction and relaxation of muscles in organ wall Segmentation- single segments of intestine alternately contract and relax

FOOD BREAKDOWN Mechanical digestion- physical processes Mixing of food in mouth by tongue, churning of food in stomach, segmentation in small intestine

FOOD BREAKDOWN Chemical Digestion Large food molecules broken down to building blocks by enzymes

Chemical digestion Proteins digested into polypeptides and peptides, then amino acids Lipids(fats) digested into fatty acids and glycerol (Alcohol)

Carbohydrates We digest disaccharides and polysaccharides Sucrose-table sugar Lactose-milk sugar Maltose- malt sugar Starch

Carbohydrates Carbohydrate units are monosaccharides Glucose- blood sugar Fructose-fruits Galactose-milk

Carbohydrates Cellulose is indigestible polysaccharide Do not provide us with nutrients Move digestion along by providing bulk in fiber to diet

ABSORPTION Transport digested end products from lumen of GI tract to blood or lymph fluid Digested foods must ender mucosal cells. Small intestine is MAJOR ABSORPTIVE SITE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Defecation Elimination of waste as feces