The Digestive System and Body Metabolism
Digestive System Accessory organs Alimentary Canal Slide 14.2b
Organs of the Alimentary Canal Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus Explain: Why the inside of your digestive tract is considered to be “outside” of you. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Mouth (Oral Cavity) Anatomy Lips (labia) – protect the anterior opening Cheeks – form the lateral walls Hard palate – forms the anterior roof Soft palate – forms the posterior roof Uvula – fleshy projection of the soft palate Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Processes of the Mouth Mastication (chewing) of food Mixing masticated food with saliva Initiation of swallowing by the tongue Allowing for the sense of taste Slide 14.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Pharynx Function Serves as a passageway for air and food Food is propelled to the esophagus by two muscle layers Longitudinal inner layer Circular outer layer Food movement is by alternating contractions of the muscle layers (peristalsis) Slide 14.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Esophagus Runs from pharynx to stomach through the diaphragm Conducts food by peristalsis (slow rhythmic squeezing) Passageway for food only (respiratory system branches off after the pharynx) Slide 14.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Layers of Alimentary Canal Organs Mucosa Small smooth muscle layer 2. Submucosa Soft connective tissue with blood vessels, nerve endings 3. Muscularis externa – smooth muscle 4. Serosa Outermost layer – visceral peritoneum Slide 14.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Layers of Alimentary Canal Organs Figure 14.3 Slide 14.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Choose the answer that lists the four layers of the wall of the alimentary canal in the appropriate order from innermost to outermost. Mucosa, submucosa, muscularis externa, and serosa Submucosa, mucosa, serosa, muscularis externa Serosa, mucosa, muscularis externa, submucosa Muscularis externa, submucosa, serosa, mucosa Answer: a. Mucosa, submucosa, muscularis externa, and serosa
Stomach Anatomy Cardiac region – near the heart Fundus Body Phylorus Pyloric Sphincter Omentum Slide 14.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Specialized Mucosa of the Stomach Simple columnar epithelium Mucous neck cells – produce a sticky alkaline mucus Gastric glands – secrete gastric juice Chief cells – produce protein-digesting enzymes (pepsinogens) Parietal cells – produce hydrochloric acid Endocrine cells – produce gastrin Slide 14.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Structure of the Stomach Mucosa Function of Pits? Glands? Figure 14.4b, c Slide 14.20b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Stomach Ulcers H. pylori bacteria Gastric ulcer lesion
Small Intestine: major digestive organ Pyloric sphincter to the ileocecal valve “Dogs Just Itch” Duodenum Jejunum Ileum Slide 14.21
Liver Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Gallbladder Pancreas Jejunum Hepatopancreatic ampulla and sphincter Main pancreatic duct and sphincter Duodenum
Villi of the Small Intestine: more surface area increased absorption Figure 14.7a Slide 14.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Structures Involved in Absorption of Nutrients Absorptive cells Blood capillaries Lacteals (specialized lymphatic capillaries) Figure 14.7b Slide 14.26 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Large Intestine: Larger in diameter, but shorter Absorption of water Eliminates indigestible food Does not participate in digestion of food Goblet cells produce mucus to act as a lubricant Figure 14.8 Slide 14.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Functions of the Large Intestine Absorption of water Eliminates indigestible food from the body as feces Does not participate in digestion of food Goblet cells produce mucus to act as a lubricant Slide 14.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Drains blood from the G.I tract to the liver to Vena Cava to Heart Hepatic Portal System Drains blood from the G.I tract to the liver to Vena Cava to Heart
Accessory Digestive Organs Salivary glands: forms bolous, amylase Teeth: masticate (chew), full set is 32 teeth Pancreas: digestive enzymes secreted into the duodenum, Insulin, Glucagons, neutralize chyme Liver: Largest gland, connected to the gall bladder , produce bile Gall bladder: Stores bile- used in lipid digestion Slide 14.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Processes of the Digestive System Peristalsis – alternating waves of contraction Segmentation – moving materials back and forth to aid in mixing Figure 14.12 Slide 14.42b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Processes of the Digestive System Mechanical digestion Chemical Digestion Enzymes break down food molecules into their building blocks Carbohydratesn to simple sugars Proteins to amino acids Fats to fatty acids and alcohols Nucleic Acids to nucleotide Slide 14.44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Processes of the Digestive System Absorption End products of digestion are absorbed in the blood or lymph Food must enter mucosal cells and then into blood or lymph capillaries Defecation Elimination of indigestible substances as feces Slide 14.45 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Control of Digestive Activity Stimuli include: Stretch of the organ pH of the contents Presence of breakdown products Reflexes include: Activation or inhibition of glandular secretions Smooth muscle activity Slide 14.47b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings