Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Digestive System Chapter 25 Human Anatomy, 3rd edition Prentice Hall, © 2001 Introduction – Structure of the digestive system • A tube that extends from mouth to anus • Accessory organs are attached – Functions include • • • • • Ingestion Movement Digestion Absorption Defecation Human Anatomy, 3rd edition Prentice Hall, © 2001 Overview of Digestive System Human Anatomy, 3rd edition Prentice Hall, © 2001 Histological Organization – The wall of the digestive tract has the same basic arrangement of tissues from the esophagus to the anal canal – Four layers (from innermost to outermost) • • • • Mucosa Submucosa Muscularis Serosa Human Anatomy, 3rd edition Prentice Hall, © 2001 Layers of the Digestive Tract Human Anatomy, 3rd edition Prentice Hall, © 2001 Layers of the Digestive Tract Human Anatomy, 3rd edition Prentice Hall, © 2001 Movement & Mixing of Digestive Materials – Peristalsis • Coordinated motion of the two muscular layers • Circular muscles contract, then longitudinal muscles – Segmentation • Mixing of food • Circular muscles in two areas contract • Longitudinal muscles alternately contract & relax Human Anatomy, 3rd edition Prentice Hall, © 2001 Peristalsis & Segmentation Human Anatomy, 3rd edition Prentice Hall, © 2001 The Oral Cavity – Functions • Take in food • Prepare food for digestion – Structure • • • • Lined with stratified squamous epithelium Lips surround the opening Roof is formed from the hard & soft palate Tongue dominates the floor Human Anatomy, 3rd edition Prentice Hall, © 2001 Oral Cavity Human Anatomy, 3rd edition Prentice Hall, © 2001 Oral Cavity Human Anatomy, 3rd edition Prentice Hall, © 2001 The Tongue – Functions • Maneuvers food – Structure • Skeletal muscle covered with mucosa • The lingual frenulum connects the tongue to the floor of the mouth • Surface – Papillae Human Anatomy, 3rd edition Prentice Hall, © 2001 The Salivary Glands – Found outside the mouth – Ducts carry saliva to the mouth – Saliva • Functions – Keeps mucous membranes moist – Lubricates food – Dissolves food – Begins carbohydrate digestion – 3 pairs • Parotid glands • Submandibular glands • Sublingual glands Human Anatomy, 3rd edition Prentice Hall, © 2001 Salivary Glands Human Anatomy, 3rd edition Prentice Hall, © 2001 Teeth – 2 sets • Deciduous (20) • Permanent (32) – Held in sockets – Gingiva surrounds the base of the teeth – Structure • Crown • Root • Neck – Composition • Dentin – primary substance in tooth • Enamel – covers crown • Cementum – covers root – Tooth decay – Wisdom teeth – 3rd molars Human Anatomy, 3rd edition Prentice Hall, © 2001 A Tooth Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pharynx and Esophagus – Food enters the esophagus from the pharynx – The esophagus is a muscular tube behind the trachea • Food is moved by peristalsis from the pharynx to the stomach • Cardiac sphincter separates esophagus from stomach Human Anatomy, 3rd edition Prentice Hall, © 2001 The Esophagus Human Anatomy, 3rd edition Prentice Hall, © 2001 The Stomach – Has the same 4 basic layers – When the stomach is empty, the mucosa lies in large folds • Rugae – Pyloric sphincter separates stomach from small intestine Human Anatomy, 3rd edition Prentice Hall, © 2001 External Anatomy of the Stomach Human Anatomy, 3rd edition Prentice Hall, © 2001 Anatomy of the Stomach Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Stomach – Mucosa is simple columnar epithelium with goblet cells – Mucosa is folded to form gastric pits • Gastric glands secrete gastric juice – Several kinds of cells in each gland produce substances that form the gastric juice » Mucus cells » Chief cells » Parietal cells » Enteroendocrine cells Human Anatomy, 3rd edition Prentice Hall, © 2001 The Stomach Wall Human Anatomy, 3rd edition Prentice Hall, © 2001 Gastric Gland Human Anatomy, 3rd edition Prentice Hall, © 2001 Functions of the Stomach – Mechanical digestion • Food reaches pylorus – Chemical digestion • Digestion of proteins – Absorption • • • • No food Water, electrolytes Some drugs Alcohol Human Anatomy, 3rd edition Prentice Hall, © 2001 The Small Intestine – About 18 feet long – 3 regions • The duodenum (= “12 fingers’ length”) – About 8 inches long – Common bile duct & pancreatic duct empty here • The jejunum (= “empty”) – About 8 feet long – Most digestion occurs here • The ileum – About 9.5 feet long – Most absorption occurs here – Ends in the ileocecal valve Human Anatomy, 3rd edition Prentice Hall, © 2001 Regions of the Small Intestine Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Small Intestine – The lining is folded into circular pleats called plicae circulares – The mucosal surface is folded into villi – The epithelial cell membranes are highly folded into microvilli – Intestinal glands are found in the crypts (“hidden place” – like gastric pits) at the base of villi • Secrete intestinal juice Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Small Intestine Human Anatomy, 3rd edition Prentice Hall, © 2001 A Villus Human Anatomy, 3rd edition Prentice Hall, © 2001 Functions of the Small Intestine – Chyme is further broken down • Proteins • Carbohydrates • Fats – Most absorption is in the small intestine Human Anatomy, 3rd edition Prentice Hall, © 2001 The Large Intestine – AKA colon – About 4.5 feet long – Mesocolon supports – Begins with the cecum • • • • • Appendix is attached Ascending colon Transverse colon Descending colon Sigmoid colon – Colon connects to the rectum – Rectum connects to the anal canal which empties to the exterior through the anus Human Anatomy, 3rd edition Prentice Hall, © 2001 The Large Intestine Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology & Functions of the Large Intestine – Mucosa - simple columnar epithelium (thin) • Completion of absorption • Formation of feces – Lots of mucus glands – Expulsion of feces from the body Human Anatomy, 3rd edition Prentice Hall, © 2001 Digestion in the Large Intestine – Mechanical • Regulated by the ileocecal valve • Mixing and peristalsis • Mass peristalsis – Chemical • Mucus secreted • No enzymes • Bacteria – prepare chyme for elimination Human Anatomy, 3rd edition Prentice Hall, © 2001 Feces Formation & Defecation – Chyme is now solid or semi-solid - feces – Large intestine absorbs any more water and electrolytes from feces – Defecation • Mass peristalsis pushes fecal material into rectum • Rectum stretches – Defecation reflex Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Large Intestine Human Anatomy, 3rd edition Prentice Hall, © 2001 Accessory Organs – Liver – Pancreas – Gall bladder Human Anatomy, 3rd edition Prentice Hall, © 2001 The Liver – Performs many life-sustaining functions, digestive and other. – Location – under the diaphragm on the left • Connected to the diaphragm by the falciform ligament – Divided into lobes • • • • Right lobe Left lobe Caudate lobe Quadrate lobe Human Anatomy, 3rd edition Prentice Hall, © 2001 The Liver Human Anatomy, 3rd edition Prentice Hall, © 2001 The Liver Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology of the Liver - Outside is a capsule - Composed of tiny lobules – Each lobule is surrounded by liver cells and sinusoids – Bile ducts run between liver cells Human Anatomy, 3rd edition Prentice Hall, © 2001 Histology and Blood Supply of the Liver Human Anatomy, 3rd edition Prentice Hall, © 2001 Functions of the Liver – Produces bile – the primary digestive function • Composition – – – – Water Bile salts Cholesterol Pigments » Bilirubin • Digestive function – Emulsification of fats Human Anatomy, 3rd edition Prentice Hall, © 2001 Other Functions of the Liver – Absorbs and stores iron, vitamins A, D, E, B7, K – Detoxifies toxins and hormones – Metabolizes proteins, carbohydrates, and lipids – Removes bacteria from the blood • Kupffer cells – Produces plasma proteins – Removes worn-out and damaged red blood cells Human Anatomy, 3rd edition Prentice Hall, © 2001 The Gallbladder – Location – underside of the left lobe of the liver – Function – to concentrate and store bile – Gallstones • Cholesterol in bile crystalizes, crystals fuse. Human Anatomy, 3rd edition Prentice Hall, © 2001 The Gallbladder Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pancreas - Location – in the curvature of the duodenum – Connected to the duodenum by the pancreatic duct – Produces pancreatic juic – Functions • Exocrine - digestion of all the nutrient groups • Endocrine – production of insulin & glucagon – Control level of blood glucose Human Anatomy, 3rd edition Prentice Hall, © 2001 The Pancreas Human Anatomy, 3rd edition Prentice Hall, © 2001