Chapter Five: Digestion and Absorption Trace the path followed by food from the mouth to the anus. Explain what is meant by peristalsis and the role of villi and microvilli. Describe and contrast digestion that takes place in the mouth, stomach, small intestine, and colon Describe the functions of the liver, gall bladder, and bile as related to digestion

Digestion and Absorption, cntd. Name and describe the functions of the two nutrient transport systems in the body. Identify the final products of digestion. Identify life style factors that affect digestion and absorption. Identify common digestive problems.

Anatomy of the Digestive Tract Mouth: Provides enzyme—salivary amylase— begins starch digestion Bolus: term given to swallowed food Esophagus: Pathway from mouth to stomach—separated from stomach by cardiac sphincter muscle Stomach: Starch digestion ceases; beginning of digestion of fats & protein by gastric juices; Vit. B12 activated by intrinsic factor; Iron may more absorbable by acidic medium; food mass now referred to as Chyme

Anatomy of Dig. Tract contd. Pylorus: sphincter muscle between stomach and small intestine Small Intestine: Enzymes from gall bladder, pancreas plus intestine completes digestion of Carbohydrates, Fats, & Protein Bile: emulsifier produced in liver that emulsifies fat—stored in gall bladder Large Intestine: Reabsorbs water and some nutrients

Involuntary Muscles & Glands Peristalsis: involuntary muscle action of digestive tract that moves food mass along the tract Glands: Exocrine: releases secretions “out” into the digestive tract, e.g. enzymes Endocrine: releases secretions “into” the blood; triggers exocrine glands to secrete

Digestive Process: Foods are broken down into basic units of energy nutrients Fat: glycerol and fatty acids Protein: amino acids Carbohydrate: monosaccharide—glucose Body organs that secrete digestive juices: Salivary glands in mouth—salivary amylase Stomach: Gastric juices--HCL Small Intestine: Digestive enzymes

Digestive Process, cntd. Liver and Pancreas: Bile and Digestive enzymes Digestion: Starts in the mouth with carbohydrate Stomach adds HCL acid, water & enzymes Mucus protects walls of stomach from being digested Small intestine: most digestion completed Colon: Reabsorbs water and mineral salts—iron; breaks down fiber Rate of Digestion affected by fat content

Absorptive Systems

Absorptive System Anatomy of the Digestive Tract Small Intestine: Surface composed of multiple folds covered with fingerlike projections called Villi Each Villi is covered with hairlike projections projections called Microvilli Surface of small intestine increased in order to better absorb nutrients

Absorptive System Circulatory System Vascular System: Transports water soluble nutrients (Carbs, Protein, Water soluble vitamins and small fat molecules) Closed system with a pump Contains Red Blood Cells (RBC) Nutrients are absorbed through the walls of the small intestine

Absorptive System, cntd. Lymphatic System Transports Fat soluble nutrients (large fat molecules and fat soluble vitamins) Open system—no pump No RBC—Lymph is a watery substance Molecules collect in duct behind the heart Enters blood stream through Subclavian Vein Lipid Transport in Vascular System Lipoproteins—fats bundles with protein HDL and LDL associated with heart disease risk

Systems at their best Life style factors can affect digestive and absorptive systems Sleep Exercise—voluntary and involuntary muscles affected State of Mind—stress Nutrition

Digestive Problems Vomiting—reverse peristalsis Adaptive mechanism to rid body of irritants Treat with rest and clear fluids Diarrhea: movement of digested particles too rapidly through tract Constipation: difficulty or pain in eliminating feces Increase fiber or fluids Natural laxatives—bran, prune juice, fruits Laxatives—only on physician’s recommendation