overview of the Digestive System

PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 22 HUMAN ANATOMY fifth edition PART 1 The Digestive System MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Overview of the Digestive System  Organs are divided into two groups  Alimentary canal  Mouth, pharynx, and esophagus  Stomach, small intestine, and large intestine  Accessory digestive organs  Teeth and tongue  Gallbladder, salivary glands, liver, and pancreas Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Alimentary Canal and Accessory Digestive Organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.1 Digestive Processes    Ingestion – occurs in the mouth Propulsion – movement of food  Peristalsis – major means of propulsion Mechanical digestion – prepares food for chemical digestion  Chewing, churning of food in stomach, segmentation  Segmentation is rhythmic local constrictions of intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes  Chemical digestion – complex molecules broken down to chemical components  Mouth  Stomach  Small intestine   Absorption – transport of digested nutrients Defecation – elimination of indigestible substances as feces Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.2 Peristalsis   Major means of propulsion Adjacent segments of the alimentary canal relax and contract Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.3a Segmentation   Rhythmic local contractions of the intestine Mixes food with digestive juices Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.3b Abdominal Regions  Four lines divide abdominal wall into 9 regions  Midclavicular lines – vertical lines of grid  Subcostal plane – superior horizontal line  Connects inferior points of costal margin  Transtubercular plane – inferior horizontal line  Connects tubercles of iliac crests Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nine Regions of Anterior Abdominal Surface Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.4a Nine Regions of Anterior Abdominal Surface  How regions relate to abdominal viscera Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.4b Abdominal Quadrants  A simpler scheme defining four quadrants Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.4c PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 22 HUMAN ANATOMY fifth edition PART 2 The Digestive System MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Wall  Same four layers from esophagus to anus  The mucosa – innermost layer  Consists of  Epithelium  Lamina propria  Muscularis mucosae  The submucosa – external to the mucosa  Contains blood and lymphatic vessels, nerve fibers Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Wall  The muscularis externa – external to the submucosa  Two layers  Circular muscularis – inner layer  Longitudinal muscularis – outer layer  The serosa – the outermost layer  Is the visceral peritoneum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.5 Smooth Muscle     Primarily found in walls of viscera Fibers elongated Have one centrally-located nucleus Grouped into sheets  Longitudinal layer – parallel to long axis of organ  Circular layer – deeper layer, fibers run around circumference of organ Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.6a, b Smooth Muscle Contraction   Myofilaments operate by interaction with cytoskeleton Dense bodies – correspond to Zdiscs of skeletal muscle Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.7a–c Innervation of Smooth Muscle   Innervated by ANS Few fibers per sheet innervated  Sheet of smooth muscle contracts as a unit  Exceptions  Iris of eye  Arrector pili muscles in skin Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.8 Nerve Plexuses    Myenteric nerve plexus  Lies between circular and longitudinal muscularis  Controls peristalsis and segmentation Submucosal nerve plexus  Lies in submucosa  Signals glands to secrete Innervation  Sympathetic and parasympathetic motor fibers  Visceral sensory fibers Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Peritoneal Cavity and Peritoneum   Peritoneum – a serous membrane  Visceral peritoneum – surrounds digestive organs  Parietal peritoneum – lines the body wall Peritoneal cavity – a slit-like potential space Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Peritoneal Cavity and Peritoneum  Mesentery – a double layer of peritoneum  Holds organs in place  Sites of fat storage  Provides a route for circulatory vessels and nerves Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.9a The Peritoneal Cavity and Peritoneum   Retroperitoneal organs  Behind the peritoneum Peritoneal organs  Digestive organs that keep their mesentery Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.9b Mesenteries  Superficial view of abdominal organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.10a Mesenteries  Lesser omentum attaches to lesser curvature of stomach Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.10b Mesenteries   Greater omentum – a “fatty apron” of peritoneum Greater omentum and transverse colon reflected Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.10c Mesenteries   Sagittal section through the abdominopelvic cavity Mesenteries attach to posterior abdominal wall Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.10d Secondarily Retroperitoneal Organs   Initially formed within peritoneum Become retroperitoneal  Fuse to posterior abdominal wall Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.11 Summary of Intraperitoneal and Secondarily Retroperitoneal Organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Table 22.1 The Mouth and Associated Organs  The mouth – oral cavity  Mucosal layer  Stratified squamous epithelium  Lamina propria  The lips and cheeks  Formed from orbicularis oris and buccinator muscles, respectively Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Mouth Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.12a Anatomy of the Mouth   The labial frenulum  Connects lips to gum The palate  Forms the roof of the mouth Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.12b The Tongue       Interlacing fascicles of skeletal muscle Grips food and repositions it Helps form some consonants Intrinsic muscles – within the tongue Extrinsic muscles – external to the tongue Lingual frenulum  Secures tongue to floor of mouth Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Superior Surface of the Tongue  Tongue papillae  Filiform papillae – no taste buds  Fungiform papillae  Circumvallate papillae   Sulcus terminalis  Marks border between mouth and pharynx Posterior 1/3 of tongue lies in oropharynx  Lined with lingual tonsil Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Superior Surface of the Tongue Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.13 The Teeth    Deciduous teeth – 20 teeth  First appear at 6 months of age Permanent teeth – 32 teeth  Most erupt by the end of adolescence Dental formula – shorthand  Way to indicate number and position of teeth  2I, 1C, 2P, 3M Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Teeth Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.14 Tooth Structure  Longitudinal section of tooth in alveolus Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.15 The Salivary Glands   Produce saliva Compound tubuloalveolar glands  Parotid glands  Parotid duct – parallel to zygomatic arch  Contains only serous cells  Submandibular glands  Lies along medial surface of mandible  Sublingual glands  Lies in floor of oral cavity  Contains primarily mucous cells Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Salivary Glands Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.16 The Pharynx  Oropharynx and laryngopharynx  Passages for air and food  Lined with stratified squamous epithelium  External muscle layer  Consists of superior, middle, and inferior pharyngeal constrictors Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Esophagus  Gross anatomy – muscular tube  Begins as a continuation of the pharynx  Joins the stomach inferior to the diaphragm  Cardiac sphincter – closes lumen to prevent stomach acid from entering esophagus Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Esophagus  Microscopic anatomy  Epithelium is stratified squamous epithelium  When empty – mucosa and submucosa in longitudinal folds  Mucous glands – primarily compound tubuloalveolar glands  Muscularis externa  Adventitia – most external layer  Skeletal muscle first third of length Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Structure of the Esophagus Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.17a, b The Stomach    Site where food is churned into chyme Secretion of pepsin begins protein digestion  Functions under acidic conditions Food remains in stomach approximately 4 hours Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Stomach Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.18a The Stomach Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.18b Microscopic Anatomy of the Stomach    Muscularis has three layers  Circular and longitudinal layers and oblique layer Epithelium is simple columnar epithelium Mucosa dotted with gastric pits  Gastric glands – deep to gastric pits Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Stomach  Gastric glands of fundus and body  Mucous neck cells  Secrete a special mucus  Parietal (oxyntic) cells  Secrete hydrochloric acid and gastric intrinsic factor  Chief (zymogenic) cells  Secrete pepsinogen Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Stomach – Microscopic Anatomy Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.19a–d The Small Intestine – Gross Anatomy    Longest portion of the alimentary canal Site of most enzymatic digestion and absorption Three subdivisions  Duodenum  Jejunum  Ileum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Duodenum   Receives digestive enzymes and bile Main pancreatic duct and common bile duct enter duodenum  Sphincters control entry of bile and pancreatic juices Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Duodenum and Related Organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.20 The Small Intestine – Microscopic Anatomy  Modifications for absorption  Circular folds (plicae circulares)  Transverse ridges of mucosa and submucosa  Villi  Finger-like projections of the mucosa  Covered with simple columnar epithelium  Microvilli  Further increase surface area for absorption Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Intestinal Wall     Absorptive cells  Uptake digested nutrients Goblet cells  Secrete mucus that lubricates chyme Enteroendocrine cells  Secrete hormones Intestinal crypts  Epithelial cells secrete intestinal juice Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Small Intestine – Structural Features Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.21a–d PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 22 HUMAN ANATOMY fifth edition PART 3 The Digestive System MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Large Intestine     Digested residue contains few nutrients Small amount of digestion by bacteria Main functions  Absorb water and electrolytes Mass peristaltic movements force feces toward the rectum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine   Subdivided into  Cecum, vermiform appendix, colon, rectum, anal canal Special features of large intestine  Teniae coli  Thickening of longitudinal muscularis  Haustra  Puckering created by teniae coli  Epiploic appendages  Fat-filled pouches of visceral peritoneum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine    Cecum  Blind pouch  Beginning of large intestine Vermiform appendix  Contains lymphoid tissue  Neutralizes pathogens Colon  Divided into distinct segments  Ascending, transverse, descending, and sigmoid colon Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine   Rectum  Descends along the inferior half of the sacrum Anal Canal  The last subdivision of the large intestine  Lined with stratified squamous epithelium Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Large Intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.22a Gross Anatomy of Large Intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.22b Vessels and Nerves of the Large Intestine  First half of large intestine  Arterial supply - superior mesenteric artery  Innervation  Sympathetic innervation – superior mesenteric and celiac ganglia  Parasympathetic innervation – vagus nerve Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Vessels and Nerves of the Large Intestine  Distal half of large intestine  Arterial supply - inferior mesenteric artery  Innervation  Sympathetic innervation – inferior mesenteric and hypogastric plexuses  Parasympathetic innervation – pelvic splanchnic nerves Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Defecation Reflex Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.23 Microscopic Anatomy of Large Intestine     Villi are absent Contains numerous goblet cells Intestinal crypts – simple tubular glands Lined with simple columnar epithelial tissue  Epithelium changes at anal canal  Becomes stratified squamous epithelium Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mucosa of the Large Intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.24 The Liver  Largest gland in the body  Performs over 500 functions  Digestive function  Bile production  Performs many metabolic functions Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Visceral Surface of the Liver Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.26 Microscopic Anatomy of the Liver   Hepatocyte – functional cells of the liver Portal triad composed of  Bile duct tributary  Branch of hepatic portal vein  Branch of hepatic artery  Kupffer cells – destroy bacteria Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Liver  Some functions of hepatocytes  Rough ER manufactures blood proteins  Smooth ER produces bile salts, detoxifies poisons  Peroxisomes detoxify poisons (alcohol)  Golgi apparatus packages secretory products  Mitochondria provide energy for liver processes  Glycosomes store sugar  Great capacity for regeneration Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Liver Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.27a, c, d The Gallbladder    Stores and concentrates bile Expels bile into duodenum  Bile emulsifies fats Cholecystokinin – released from enteroendocrine cells in response to fatty chyme Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Gallbladder Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.20 PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 22 HUMAN ANATOMY fifth edition PART 4 The Digestive System MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Pancreas  Exocrine function  Acinar cells make, store, and secrete pancreatic enzymes  Enzymes are activated in the duodenum  Endocrine function  Produces insulin and glucagon  Regulates blood sugar Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Exocrine Pancreas: Histology Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.29a, b Disorders of the Digestive System  Intestinal obstruction  Mechanical obstructions  Adhesions, tumors, or foreign objects  Nonmechanical obstruction  Halt in peristalsis  Trauma  Intestines touched during surgery Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Digestive System  Inflammatory bowel disease  Inflammation of intestinal wall  Crohn’s disease  Ulcerative colitis  Viral hepatitis  Jaundice and flu-like symptoms  Major types – A, B, C, and G Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Digestive System  Cystic Fibrosis and the Pancreas  Pancreatic ducts become blocked with mucus  Clogged ducts prevent pancreatic juices from entering small intestine  Leads to malabsorption of fats and other nutrients Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Embryonic Development of the Digestive System   Alimentary canal formed in week three  Encloses tubular portion of yolk sac Vitelline duct  Landmark dividing into three regions  Forgut  Midgut  Hindgut Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Embryonic Development of the Digestive System Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.30a, b The Digestive System in Later Life   Middle age – gallstones and ulcers Old age – activity of digestive organs decline  Fewer digestive juices and enzymes produced  Absorption is less efficient  Dehydration of fecal mass leads to constipation  Diverticulosis and cancer of digestive organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings