PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Tenth Edition Shier w Butler w Lewis Chapter 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 17 Digestive System Functions of Digestive System ingestion mechanical digestion chemical digestion propulsion absorption defecation

Major Organs

Alimentary Canal Wall

Movements of the Tube mixing movements peristalsis

Innervation of the Tube submucosal plexus – controls secretions myenteric plexus – controls gastrointestinal motility parasympathetic impulses – increase activities of digestive system sympathetic impulses – inhibit certain digestive actions

Palate roof of oral cavity

Salivary Glands

Secretions of Salivary Glands Parotid glands clear water, serous fluid rich in amylase Sublingual glands primarily mucus most viscous Submandibular glands primarily serous fluid some mucus

Swallowing Mechanism soft palate and uvula raise hyoid bone and larynx elevate epiglottis closes off top of trachea longitudinal muscles of pharynx contract inferior constrictor muscles relax and esophagus opens peristaltic waves push food through pharynx

Swallowing Mechanism

Esophagus

Stomach

Lining of Stomach

Gastric Secretions pepsinogen from chief cells inactive form of pepsin mucus from goblet cells and mucous glands protective to stomach wall pepsin from pepsinogen in presence of HCl protein splitting enzyme intrinsic factor from parietal cells required for vitamin B12 absorption hydrochloric acid from parietal cells needed to convert pepsinogen to pepsin

Phases of Gastric Secretion Cephalic phase triggered by smell, taste, sight, or thought of food parasympathetic impulses trigger gastric juice secretion Gastric phase triggered by presence of food in stomach gastrin released gastric juice secreted Intestinal phase triggered by movement of food into small intestine intestinal cells release intestinal gastrin secretion of gastric juice

Regulation of Gastric Secretions

Gastric Absorption some water certain salts certain lipid-soluble drugs alcohol

Mixing and Emptying Actions

Enterogastric Reflex regulates the rate at which chyme leaves the stomach

Pancreas

Pancreatic Juice pancreatic amylase – splits glycogen into disaccharides pancreatic lipase – breaks down triglycerides trypsin, chymotrypsin, and carboxypeptidase – digest proteins nucleases – digest nucleic acids bicarbonate ions – make pancreatic juice alkaline

Regulation of Pancreatic Secretions acidic chyme stimulates release of secretin secretin stimulate release of pancreatic juice

Liver

Hepatic Lobule

The Paths of Blood and Bile in Hepatic Lobule

Liver Functions produces glycogen from glucose breaks down glycogen into glucose converts noncarbohydrates to glucose oxidizes fatty acids synthesizes lipoproteins, phospholipids, and cholesterol converts carbohydrates and proteins into fats deaminates amino acids forms urea synthesizes plasma proteins converts some amino acids to other amino acids stores glycogen, vitamins A,D, B12, iron, and blood phagocytosis of worn out RBCs and foreign substances removes toxins from blood produces and secretes

Composition of Bile water bile salts bile pigments cholesterol emulsification of fats absorption of fatty acids, cholesterol, and fat-soluble vitamins bile pigments cholesterol electrolytes

Gallbladder

Regulation of Bile Release fatty chyme entering duodenum stimulate gallbladder to release bile

Three Parts of Small Intestine

Mesentery suspends portions of the small intestine from the posterior abdominal wall

Intestinal Villus

Intestinal Epithelium

Wall of Small Intestine

Secretions of Small Intestine peptidase – breaks down peptides into amino acids sucrase, maltase, lactase – break down disaccharides into monosaccharides lipase – breaks down fats into fatty acids and glycerol enterokinase – converts trypsinogen to trypsin somatostatin – hormone that inhibits acid secretion by stomach cholecystokinin – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, stimulates gallbladder to release bile secretin – stimulates pancreas to release bicarbonate ions in pancreatic juice

Regulation of Small Intestinal Secretions mucus secretion stimulated by presence of chyme in small intestine distension of intestinal wall activates nerve plexuses in wall of small intestine parasympathetics trigger release of intestinal enzymes

Absorption in the Small Intestine monosaccharides and amino acids through facilitated diffusion and active transport absorbed into blood electrolytes and water through diffusion, osmosis, and active transport absorbed into blood

Absorption in the Small Intestine fatty acids and glycerol several steps absorbed into lymph and blood

Movements of the Small Intestine mixing movements peristalsis – pushing movements segmentation – ringlike contractions overdistended wall triggers peristaltic rush resulting in diarrhea

Large Intestine

Large Intestinal Wall

Functions of Large Intestine little or no digestive function absorbs water and electrolytes secretes mucus houses intestinal flora forms feces carries out defecation

Movements of Large Intestine slower and less frequent than those of small intestine mixing movements peristalsis mass movements usually follow meals

Feces water electrolytes mucus bacteria bile pigments altered by bacteria provide color smell produced by bacterial compounds

Clinical Application Hepatitis inflammation of the liver most commonly caused by viral infection can be caused by reactions to drug, alcoholism or autoimmunity Signs and Symptoms headache low fever fatigue vomiting rash foamy urine pale feces jaundice pain Hepatitis A – not washing hands or eating raw shellfish Hepatitis B – chronic; serum Hepatitis C – serum Hepatitis D – very severe; only produces symptoms if infected with B; serum Hepatitis E, F, G – more rare