BSC 2086 01 Anatomy and Physiology II Spring 2013 16 The Digestive System Part 1 2012 Pearson Education Inc An Introduction to the Digestive System Learning Outcomes 24 1 Identify the organs of the digestive system list their major functions describe the functional histology of the digestive tract and outline the mechanisms that regulate digestion 24 2 Discuss the anatomy of the oral cavity and list the functions of its major structures and regions 2012 Pearson Education Inc 24 1 The Digestive Tract The Digestive Tract Also called gastrointestinal GI tract or alimentary canal Is a muscular tube Extends from oral cavity to anus Passes through pharynx esophagus stomach and small and large intestines Acquires nutrients from environment Provides substrates for catabolic reactions break down substances to provide energy cells need to function and to perform anabolic reactions that build macromolecules 2012 Pearson Education Inc Figure 24 1 The Components of the Digestive System Major Subdivisions of the Digestive Tract Oral Cavity Teeth Tongue Mechanical processing moistening mixing with salivary secretions Pharynx Muscular propulsion of materials into the esophagus Esophagus Transport of materials to the stomach Stomach Chemical breakdown of materials by acid and enzymes mechanical processing through muscular contractions Small Intestine Enzymatic digestion and absorption of water organic substrates vitamins and ions Large Intestine Enzymatic digestion and absorption of water organic substrates vitamins and ions Mouth Anus 2012 Pearson Education Inc Figure 24 1 The Components of the Digestive System 2012 Pearson Education Inc Accessory Organs of the Digestive System Salivary glands Secretion of lubricating fluid containing enzymes that break down carbohydrates Liver Secretion of bile important for lipid digestion storage of nutrients many other vital functions Gallbladder Storage and concentration of bile Pancreas Exocrine cells secrete buffers and digestive enzymes endocrine cells secrete hormones 24 1 The Digestive Tract Six Functions of the Digestive System 1 Ingestion Occurs when materials enter digestive tract via the mouth 2 Mechanical processing crushing and shearing makes materials easier to propel along digestive tract 3 Digestion chemical breakdown of food into small organic fragments for absorption by digestive epithelium 2012 Pearson Education Inc 24 1 The Digestive Tract Six Functions of the Digestive System 4 Secretion the release of water acids enzymes buffers and salts by epithelium of digestive tract or glandular organs 5 Absorption movement of organic substrates electrolytes vitamins and water across digestive epithelium and into interstitial fluid of digestive tract 6 Excretion removal of waste products from body fluids Process called defecation removes feces 2012 Pearson Education Inc 24 1 The Digestive Tract The Lining of the Digestive Tract Safeguards surrounding tissues against 1 Corrosive effects of digestive acids and enzymes 2 Mechanical stresses such as abrasion 3 Bacteria either ingested with food or that reside in digestive tract Digestive epithelium and its secretions provide nonspecific defense 2012 Pearson Education Inc 24 1 The Digestive Tract The Digestive Organs and the Peritoneum Lined with serous membrane consisting of two parts 1 Serosa or visceral peritoneum Covers organs within peritoneal cavity 2 Parietal peritoneum Lines inner surfaces of body wall Peritoneal fluid produced by serous membrane lining Provides essential lubrication reduces friction irritation Separates parietal and visceral surfaces Ascites excess peritoneal fluid causing abdominal swelling Caused by liver kidney heart disease can distort internal organs and cause heartburn indigestion lower back pain 2012 Pearson Education Inc 24 1 The Digestive Tract Mesenteries double sheets of peritoneal membrane Suspend portions of digestive tract within peritoneal cavity abdominal cavity lined by serious membrane by sheets of serous membrane that connect parietal peritoneum with visceral peritoneum Stabilize positions of attached organs Prevent intestines from becoming entangled Peritonitis inflammation of peritoneal membrane caused by physical damage rupture of stomach intestine appendix chemical irritation bacterial invasion Can be fatal 2012 Pearson Education Inc 24 1 The Digestive Tract The Lesser Omentum Stabilizes position of stomach Provides access route for blood vessels and other structures entering or leaving liver The Falciform Ligament Helps stabilize position of liver Relative to diaphragm and abdominal wall Both are derived from the ventral mesentery found during embryonic development 2012 Pearson Education Inc 24 1 The Digestive Tract The Dorsal Mesentery Enlarges to form an enormous pouch called the greater omentum Extends inferiorly between the body wall and the anterior surface of small intestine Hangs like an apron from lateral and inferior borders of stomach 2012 Pearson Education Inc 24 1 The Digestive Tract Adipose Tissue in Greater Omentum Conforms to shapes of surrounding organs Pads and protects surfaces of abdomen Provides insulation to reduce heat loss Stores lipid energy reserves forms the beer belly 2012 Pearson Education Inc 24 1 The Digestive Tract The Mesentery Proper thick mesenterial sheet Provides stability permits some independent movement Suspends all but first 25 cm 10 in of small intestine Is associated with initial portion of small intestine duodenum and pancreas Fuses with posterior abdominal wall locking structures in position Mesocolon mesentery associated with a portion of the large intestine 2012 Pearson Education Inc Figure 24 2b Mesenteries Lesser omentum Transverse colon Ascending colon Mesentery proper mesenterial sheet 2012 Pearson Education Inc Greater omentum cut Transverse mesocolon Mesocolon of ascending and descending colons fused to posterior portion of the parietal peritoneum Descending colon Small intestine Sigmoid colon A diagrammatic view of the organization of mesenteries in an adult Figure 28 2c Mesenteries Falciform ligament Inferior vena cava Coronary ligament of liver Right kidney Duodenum Position of ascending colon Root of mesentery proper Rectum Urinary bladder An anterior view of the empty peritoneal cavity showing the attachment of mesenteries to the posterior body wall 2012 Pearson Education Inc Diaphragm Esophagus Pancreas Left kidney Attachment of transverse mesocolon Superior mesenteric artery and vein Position of
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