The Human Body: From Food to Fuel Chapter 4 1

The Gastrointestinal Tract Organization Mouth  anus Accessory organs Salivary glands, liver, pancreas, gallbladder 2

Organization of the Gastrointestinal Tract Functions Ingestion Transport Secretion Absorption Movement Elimination 3

Organization of the Gastrointestinal Tract Layers Mucosa Circular muscle Longitudinal muscle Spincter 4

Overview of Digestion Physical movement Chemical breakdown Peristalsis Segmentation Chemical breakdown Enzymes Other secretions Acid Base Bile Mucus 5

Overview of Absorption The road to nutrition absorption Passive diffusion Facilitated diffusion Active transport 6

Assisting Organs Salivary glands Moisten food Supply enzymes Liver Produces bile “Chemical factory” Gallbladder Stores and secretes bile Pancreas Secretes bicarbonate Secretes enzymes 7

Putting It All Together: Digestion and Absorption Mouth Enzymes Salivary amylase acts on starch Lingual lipase acts on fat Saliva Moistens food for swallowing Esophagus Transports food to stomach Esophageal sphincter 8

Putting It All Together: Digestion and Absorption Stomach Hydrochloric acid prepares protein for digestion and activates enzymes Pepsin begins protein digestion Gastric lipase has some fat digestion Gastrin (hormone) stimulates gastric secretion and movement Intrinsic factor is needed for absorption of vitamin B12 9

Putting It All Together: Digestion and Absorption Small intestine Sections of small intestine Duodenum, jejunum, ileum Digestion Bicarbonate neutralizes stomach acid Pancreatic and intestinal enzymes Carbohydrates Fat Protein 10

Putting It All Together: Digestion and Absorption Small intestine Absorption Folds, villi, and microvilli expand absorptive surface Most nutrients absorbed here Fat-soluble nutrients go into lymph Other nutrients go into blood 11

Putting It All Together: Digestion and Absorption Large intestine Digestion Nutrient digestion already complete Some digestion of fiber by bacteria Absorption Water Sodium, potassium, chloride Vitamin K (produced by bacteria) Elimination 12

Circulation of Nutrients Vascular system Veins and arteries Carries oxygen and nutrients to tissues Removes wastes Lymphatic system Vessels that drain lymph 13

Circulation of Nutrients Excretion and elimination Lungs Excrete water and carbon dioxide Kidneys filter blood Excrete waste; maintain water and ion balance 14

Signaling Systems: Command, Control, Defense Nervous system Regulates GI activity Enteric nervous system Autonomic nervous system Hormonal system Increases or decreases GI activity 15

Signaling Systems: Command, Control, Defense Immune system Protects us from foreign invaders Role of GI tract Barrier Immune response Natural killer cells Macrophages Location of lymphoid tissues Lymphocytes Antibodies 16

Influences on Digestion and Absorption Psychological influences Taste, smell, and presentation of food Chemical influences Type of protein you eat and the way it is prepared Bacterial influences Hydrochloric acid 17

Nutrition and GI Disorders Constipation Hard, dry, infrequent stools Reduced by high fiber, fluid intake, exercise Diarrhea Loose, watery, frequent stools Symptom of diseases/infections Can cause dehydration Broth, tea, toast, and other low-fiber foods can help reduce 18

Nutrition and GI Disorders Diverticulosis Pouches along colon High-fiber diet reduces formation Heartburn and GERD Reduced by smaller meals, less fat 19

Nutrition and GI Disorders Irritable bowel syndrome Stress and certain foods aggravate the symptoms Controlled by diet and lifestyle modifications Reduce stress 20

Nutrition and GI Disorders Colorectal cancer Fiber-rich diet may reduce risk Gas Most foods that contain carbohydrates can cause Ulcers Bacterial cause (H. Pylori) 21

Nutrition and GI Disorders Functional dyspepsia Chronic pain in the upper abdomen Treat with medicine and stress-reduction 22