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Chapter 10
The Gastrointestinal System
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Normal Gastrointestinal (Alimentary) System
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Typical Structure
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Main Functions
Ingestion Mastication (chewing) Deglutition (swallowing) Digestion Absorption Excretion
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Overview of Major Diseases
Dental caries, gum disease Infectious diseases (e.g., gastroenteritis) Circulatory disorders, hemorrhagic lesions Multifactorial disorders (e.g., peptic ulcer, inflammatory bowel disease) Obstructive disorders Functional disorders (e.g., indigestion, malabsorption) Neoplasms
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Main Exocrine & Endocrine Products
Salivary gland: amylase Stomach: pepsin, HCl, gastrin, intrinsic factor Small intestine: enterokinase, cholecystokinin, secretin
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Diseases of the Oral Cavity
Developmental Abnormalities Inflammation Dental Caries Periodontal Disease Stomatitis Oral Cancer
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Cleft Lip
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Dental & Periodontal Diseases
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Stomatitis
Herpesvirus infection Candida albicans infection (thrush) Aphthous stomatitis (canker sores)
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Oral Cancer
Most tumors histologically classified as squamous cell carcinomas Often related to tobacco smoking Morphologically present as:
Leukoplakia Erythroplakia Ulcer Crater Nodule
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Oral Cancer (Contd)
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Salivary Gland Diseases
Sialadenitis: infectious or autoimmune (Sjgrens disease) Clinically presents as swelling of glands or xerostomia Neoplasms
May affect major or minor salivary glands Most (>60%) benign Most common tumor: pleomorphic adenoma
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Diseases of the Esophagus: Clinical Presentations
Dysphagia Esophageal (retrosternal) pain Aspiration or regurgitation
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Diseases of the Esophagus
Developmental abnormalities: atresia with or without esophageal-tracheal fistula Hiatal Hernia Motility Disorders (Achalasia) Esophagitis Circulatory Disturbances (Varices) Carcinoma
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Esophageal Atresia
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Hiatal Hernia
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Achalasia
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Esophageal Varices
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Esophagitis
Reflux of gastric juice (peptic esophagitis) Infection: viruses, fungi (immunosuppressed persons), bacterial superinfection Chemical irritants: exogenous chemicals or drugs
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Carcinoma of the Esophagus
Accounts for 4% of all cancers: 8000 cases per year in U.S. Higher incidence in Asia & Africa than in U.S. & Europe Correlates with alcohol, tobacco abuse More common in men than women More common in blacks than whites Poor prognosis: avg. survival = 2 years
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Carcinoma of the Esophagus (Contd)
Squamous cell carcinoma in upper or lower esophagus Adenocarcinoma in lower esophagus developing in Barretts esophagus
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Diseases of Stomach & Duodenum: Symptoms
Pain: midline, upper abdomen Vomiting Bleeding: acute with hematemesis or chronic with melena Dyspepsia Systemic consequences: iron deficiency anemia caused by chronic blood loss, vitamin B12 malabsorptionrelated megaloblastic anemia
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Developmental Abnormality
Most important: congenital stenosis
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Gastritis
Acute (erosive): stress, shock, food, exogenous chemicals, drugs
Erosions Ulcerations
Chronic Ch i atrophic t hi gastritis t iti with ith & without ith t intestinal metaplasia
Helicobacter pylori related Autoimmune (with pernicious anemia)
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Peptic Ulcer: Etiology & Pathogenesis
Multifactorial Contributing factors include:
Gastric juice: HCl, pepsin Mucosal barrier defects: stress, shock, NSAIDs, smoking ki reduce d resistance i t Helicobacter pylori: found in most patients
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Peptic Ulcer: Macroscopic Features
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Peptic Ulcer: Microscopic Features
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Complications of Peptic Ulcer Disease
Hemorrhage (most common): hematemesis, melena, iron deficiency anemia Penetration into the pancreas: acute pancreatitis Perforation: peritonitis Cicatrization: stenosis
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Duodenal Ulcer
An interactive video titled Duodenal Ulcer can be viewed by clicking Student Resources/Prepare for Class, Clinical or Lab/Animations. Instructors can click Instructor Resources/Prepare for Class, Clinical or Lab/Animations.
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Gastric Tumors
Benign epithelial tumors: polyps (e.g., hyperplastic, tubular, villous) Benign stromal tumors (e.g., leiomyoma) Malignant tumors
Adenocarcinoma (most common) Lymphoma
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Carcinoma of the Stomach
Common; affects 25,000 persons, causes 14,000 deaths yearly in U.S. 8 times more common in Japan, Chile Incidence has decreased over past 70 years in U U.S. S Etiology is unknown: suspect nitrosamines in food, maybe H. pylori
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Gastric Carcinoma: Macroscopic Features
Forms
Superficial Polypoid Ulcerated Diffusely infiltrating (linitis plastica) Adenocarcinoma
Histology
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Diseases of the Intestines
Developmental abnormalities: Hirschsprungs disease, congenital diverticula (e.g., Meckels) Diverticulosis, obstructions, hernias Vascular disorders Inflammatory bowel disease Infections, including peritonitis Malabsorption syndrome Neoplasms
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Diverticulitis
An interactive video titled Diverticulitis can be viewed by clicking Student Resources/Prepare for Class, Clinical or Lab/Animations. Instructors can click Instructor Resources/Prepare for Class, Clinical or Lab/Animations.
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Hirschsprungs Disease
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Diverticulosis of the Colon
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Intestinal Vascular Diseases
Hemorrhoids Angiodysplasia Ischemic bowel disease Chronic ischemia Acute thrombosis of mesenteric arteries, veins Nonocclusive intestinal infarcts
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Mesenteric Thrombosis
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Inflammatory Bowel Disease
Crohns disease: incidence 70150 per 100,000 persons per year in U.S. Ulcerative colitis: incidence 2040 per 100,000 persons per year in U.S. Cause unknown; may be familial _____________________________________
Note: Symptoms may overlap; in 20% of cases, impossible to tell diseases apart
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Crohns Disease
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Ulcerative Colitis
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Features of Crohns Disease & Ulcerative Colitis
Clinical Features Crohns Disease Familial Peak age Immune disturbances Extraintestinal complications Treatment ++ 15 25 years 1525 + + + ++ 15 25 years 1525 + + +
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Ulcerative Colitis
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Features of Crohns Disease & Ulcerative Colitis (Contd)
Pathology Distribution Transmural Granuloma Fistula Megacolon Cancer Crohns Disease Segmental, including ileum ++ + + ( ) + Ulcerative Colitis Diffuse, colon only ( ) ( ) ( ) + ++
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Gastrointestinal Infections
Food poisoning: bacterial toxins Viral infections Infectious diarrhea Small-intestine infection: E. coli, Vibrio cholerae, Giardia lamblia, rotavirus Large-intestine infection: E. coli, Shigella, Norwalk virus, Entamoeba
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Comparison of Diarrhea
Stool Characteristic Volume A Appearance Blood Leukocytes Proctoscopy Small Intestine Large W Watery Rare ( ) ( ) Large Intestine Small M Mucoid id Common +/ or + +
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Causes of Diarrhea
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Acute Appendicitis
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Acute Appendicitis (Contd)
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Acute Appendicitis (Contd)
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Acute Infectious Peritonitis: Etiology & Pathogenesis
Rupture of stomach Spread of infection from fallopian tubes Rupture of abscess Infection of preexisting ascites
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Acute Sterile (Noninfectious) Peritonitis: Etiology & Pathogenesis
Acute pancreatitis Rupture of the gallbladder Postsurgical peritonitis by talc or chemicals used during surgery
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Causes of Intestinal Obstruction
Paralytic ileus Mechanical (obstructive) ileus
Atresia or stenosis Stricture I t Intussusception ti Volvulus Hernia Adhesions Neoplasms
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Intestinal Obstructions: Hernia
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Intestinal Obstructions: Intussusception
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Intestinal Obstructions: Volvulus
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Pathogenesis of Malabsorption
Malabsorption results from abnormalities:
Intraluminal digestion of food Uptake, processing of nutrients within intestinal cells Transport of nutrients from intestine to liver
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Malabsorption
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Malabsorption Resulting from Defective Intraluminal Digestion
Deficiency of gastric juices: postgastrectomy conditions, atrophic gastritis Deficiency of bile: biliary obstruction, liver disease, Crohns disease Deficiency of pancreatic juices: chronic pancreatitis Bacterial overgrowth: Giardia lamblia
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Malabsorption Resulting from Defective Uptake of Nutrients
Celiac sprue Tropical sprue Infectious enteritis (e.g., E. coli, rotavirus) Crohns disease Whipples disease Congenital abetalipoproteinemia Short bowel syndrome (after surgical resection)
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Malabsorption Resulting from Defective Transport of Nutrients (Contd)
Gastrointestinal lymphoma Congestive heart failure with intestinal ischemia Scleroderma Amyloidosis
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Intestinal Neoplasms
Colon most often affected May be sporadic or familial (S:F = 8:2) May be benign or malignant (B:M = 3:1) May be solitary or multiple May be primary or secondary (P > S) Epithelial tumors (adenomas, carcinomas): account for 90% of all tumors; more common than lymphomas or mesenchymal tumors (benign soft tissue tumor, e.g., lipoma, leiomyoma, sarcomas)
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Carcinoma of the Large Intestine
Third most common cancer of internal organs Affects 190,000 persons per year in U.S.
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Colon Cancer: Etiology
Mostly unknown etiology Genetic factors (play important role)
Familial polyposis coli Gardners syndrome H dit Hereditary nonpolyposis l i colorectal l t l cancer
Dietary factors (Western diet: low fiber, high carbohydrate, high fat content) Interaction of carcinogens, oncogenes, tumor suppressor genes
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Classification of Intestinal Tumors
Non-neoplastic polyps: hyperplastic polyp, inflammatory polyp, juvenile polyp, PeutzJeghers polyp, lymphoid polyp Benign neoplasms: tubular adenoma, villous adenoma, tubulovillous adenoma, benign stromal tumors (e.g., leiomyoma) Malignant neoplasms: adenocarcinoma, carcinoid, lymphoma, sarcoma
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Intestinal Polyps
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Adenocarcinoma of the Colon
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Adenocarcinoma of the Cecum: Macroscopic Features
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Adenocarcinoma of the Sigmoid Colon: Macroscopic Features
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Adenocarcinoma of the Colon: Microscopic Features
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Gastrointestinal Carcinoids
90% occur in intestines Appendix: most common site of origin Smaller than 2 cm = benign; larger ones can metastasize May be multiple, especially in terminal ileum, stomach cancers Composed of neuroendocrine cells that contain granules visible by electron microscopy, polypeptide hormones
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Gastrointestinal Carcinoids: Clinical Features
Small tumors (<2 cm) = benign; larger ones metastasize (low-grade malignancy) Tumors secrete serotonin, polypeptide hormones; cause diarrhea, hypermotility of intestines Tumors metastasizing to liver cause carcinoid syndrome; adversely affect right-side heart valves
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Submucosal Carcinoid
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Carcinoid: Microscopic Features
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