PART 1 The Digestive System

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 Figure 22.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Ingestion – occurs in the mouth Propulsion – movement of food 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

Absorption – transport of digested nutrients 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 Figure 22.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Major means of propulsion Peristalsis Major means of propulsion Adjacent segments of the alimentary canal relax and contract Figure 22.3a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Rhythmic local contractions of the intestine Segmentation Rhythmic local contractions of the intestine Mixes food with digestive juices Figure 22.3b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Four lines divide abdominal wall into 9 regions 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 Figure 22.4a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Nine Regions of Anterior Abdominal Surface How regions relate to abdominal viscera Figure 22.4b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

A simpler scheme defining four quadrants Abdominal Quadrants A simpler scheme defining four quadrants Figure 22.4c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

PART 2 The Digestive System

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 Figure 22.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Primarily found in walls of viscera Fibers elongated 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 Figure 22.6a, b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Smooth Muscle Contraction Myofilaments operate by interaction with cytoskeleton Dense bodies – correspond to Z-discs of skeletal muscle Figure 22.7a–c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.8 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Myenteric nerve plexus 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 Figure 22.9a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Peritoneal Cavity and Peritoneum Retroperitoneal organs Behind the peritoneum Peritoneal organs Digestive organs that keep their mesentery Figure 22.9b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Superficial view of abdominal organs Mesenteries Superficial view of abdominal organs Figure 22.10a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lesser omentum attaches to lesser curvature of stomach Mesenteries Lesser omentum attaches to lesser curvature of stomach Figure 22.10b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Greater omentum – a “fatty apron” of peritoneum Mesenteries Greater omentum – a “fatty apron” of peritoneum Greater omentum and transverse colon reflected Figure 22.10c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Sagittal section through the abdominopelvic cavity Mesenteries Sagittal section through the abdominopelvic cavity Mesenteries attach to posterior abdominal wall Figure 22.10d Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Secondarily Retroperitoneal Organs Initially formed within peritoneum Become retroperitoneal Fuse to posterior abdominal wall Figure 22.11 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Summary of Intraperitoneal and Secondarily Retroperitoneal Organs Table 22.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.12a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of the Mouth The labial frenulum The palate Connects lips to gum The palate Forms the roof of the mouth Figure 22.12b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Interlacing fascicles of skeletal muscle Grips food and repositions it 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 Figure 22.13 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Deciduous teeth – 20 teeth Permanent teeth – 32 teeth 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 Figure 22.14 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Longitudinal section of tooth in alveolus Tooth Structure Longitudinal section of tooth in alveolus Figure 22.15 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Compound tubuloalveolar glands 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 Figure 22.16 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Oropharynx and laryngopharynx 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

Gross anatomy – muscular tube 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 Skeletal muscle first third of length Adventitia – most external layer Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Microscopic Structure of the Esophagus Figure 22.17a, b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Site where food is churned into chyme 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 Figure 22.18a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Stomach Figure 22.18b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.19a–d Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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

Receives digestive enzymes and bile 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 Figure 22.20 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.21a–d Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

PART 3 The Digestive System

Digested residue contains few nutrients 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 Figure 22.22a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Gross Anatomy of Large Intestine Figure 22.22b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.23 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.24 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Largest gland in the body 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 Figure 22.26 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.27a, c, d Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Stores and concentrates bile Expels bile into duodenum 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 Figure 22.20 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

PART 4 The Digestive System

The Pancreas Exocrine function Endocrine 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 Figure 22.29a, b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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 Figure 22.30a, b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

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