Gastrointestinal Pathophysiology

Anatomy and Physiology of the GI System, Hormonal Control, Upper GI Tract Disorders, Gallbladder Disorders, Liver Disorders, Pancreatic Disorders, Lower GI Tract Disorders

1. Gastrointestinal Pathophysiology

2. The Stomach 4 layers Mucosa Submucosa Circular muscular layer Longitudinal muscle layer Serosa Peristalsis Key physiologic process Involuntary contractions of the stomach Occur in circular and longitudinal smooth muscle layers

3. Cells of the Stomach Gastrin Cells, G Cells Initiated by food entering the stomach Stimulate parietal cells and chief cells Intrinsic Factor, Parietal Cells Needed for the absorption of vitamin B12 HCl Cells, Parietal Cells Activate pepsinogen to create an optimal pH of 2 Denature proteins Pepsinogen, Chief Cells Not activated until stomach acid has a pH of 6

4. The Liver: Functions Storage of nutrients Maintains blood glucose Blood reservoir Produces bile, plasma proteins, blood clotting factors, cholesterol, and lipoproteins Takes part in metabolic processes

5. The Liver: Storage Processes Glycogenesis Glucose is converted to glycogen When glycogen supply is low Glyconeogenesis Proteins and fats are converted to glycogen Glycogenolysis Glycogen is converted to glucose Maintain blood glucose levels

6. Pancreas Exocrine Organ because it secretes digestive enzymes and electrolytes Endocrine Organ because it secretes insulin and glucagon Important Molecules – Trypsin, chymotrypsin, carboxypeptidase Break proteins Ribonuclease Break nucleic acids Pancreatic Amylase Break starch Lipase Break lipids

7. Gallbladder Stores bile, fluids, fat, and cholesterol Bile breaks down fat from food in your intestine Delivers bile into the small intestine

8. GI Tract Ileum Major site of nutrient absorption Occurs in the folds of mucosal linings (villi) Large Intestine Fluid and electrolyte reabsorption Movement is slow to allow for absorption of water Vitamin K synthesis is essential for blood clotting

9. Small Intestine Large Intestine

10. Neural Control of the GI Tract Parasympathetic Nervous System Vagus Nerve Increased gastric motility Increased gastric acid secretions Sympathetic Nervous System Inhibits gastrointestinal activity

11. Hormonal Control of the GI Tract Gastrin Increases gastric motility Promotes stomach emptying Secretin Decreases gastric acid secretions Cholecystokinin Inhibits gastric emptying

12. Upper GI Tract Disorders Dysphagia Difficulty swallowing Causes: neurological deficit, muscular disorder, or mechanical obstruction Esophageal Cancer Squamous cells in the distal esophagus. Poor prognosis. Causes: chronic irritation, chronic esophagitis, hiatal hernia Hiatal Hernia Part of the stomach protrudes into the thoracic cavity

13. Upper GI Tract Disorders GERD Gastric substances reflux into the distal esophagus, often seen with hiatal hernia Cause: decrease competence of the lower esophageal sphincter Gastritis Stomach mucosa is inflamed, can be acute or chronic Causes of acute gastritis: food allergies, spicy food, excessive alcohol, or ulcerogenic drugs Causes of chronic: idiopathic or helicobacter pylori infection Gastroenteritis Inflammation of the stomach and intestine

14. Upper GI Tract Disorders Peptic Ulcers Erosion in the mucosa is common in the proximal duodenum and the antrum of the stomach Rarely found in the large intestine Causes: H. pylori infection, increased acid-pepsin secretions, inadequate blood supply, excessive glucocorticoid secretion, and ulcerogenic substances

15. Upper GI Tract Disorders Stress Ulcers Rapid onset, may form within hours of the precipitating event Causes Severe Trauma Curling’s Ulcers – Burns Cushing’s Ulcers – Head Injury Systemic Causes Ischemic Ulcers – Hemorrhage, Sepsis

16. Upper GI Tract Disorders Gastric Cancer Primarily in the mucous glands and in the antrum or pyloric area of the stomach Poor prognosis Pyloric Stenosis Narrowing and obstruction of pyloric sphincter May be a developmental anomaly or acquired later in life

17. Gallbladder Disorders Cholelithiasis Formation of gallstones Cholecystitis Inflammation of gallbladder and cystic duct Cholangitis Inflammation related to bile duct infection Choledocholithiasis Obstruction of biliary tract by gallstones, due to the presence of larger stones

18. Liver Disease Jaundice – yellowish color of skin, sign of disease Prehepatic Unconjugated bilirubin is elevated Cause: excessive destruction of red blood cells Intrahepatic Unconjugated and conjugated bilirubin are elevated Cause: disease or damage to hepatocytes Posthepatic Conjugated bilirubin is elevated Cause: obstruction of bile flow into the gallbladder or duodenum

19. Liver Disease Hepatitis – inflammation of the liver Mild Impaired hepatocyte function Severe Impaired hepatocyte function Necrosis and obstruction of blood and bile flow Cause Idiopathic – fatty liver Infection – viral or non-viral

20. Liver Disease: Viral Hepatitis Hepatitis A Infectious hepatitis. RNA virus. Transmitted by fecal-oral route in areas of inadequate sanitation. No carrier or chronic stage. Vaccine available. Hepatitis B Serum hepatitis. DNA virus. Incubation period of 2 months. Primarily transmitted through infectious blood but can also be transmitted through sexual contact or from mother to fetus. Carriers are asymptomatic but contagious. Vaccine is available. Ascites in Chronic Hepatitis B Engorgement of blood vessels so that toxins can no longer be filtered

21. Liver Disease: Viral Hepatitis Hepatitis C RNA virus. Most common type. Transmitted via blood transfusion. Has carrier state. Increases risk of hepatocellular carcinoma. Hepatitis D Delta virus. Incomplete RNA virus – needs hepatitis B to produce an active infection. Transmitted through blood. Hepatitis E RNA virus. No carrier or chronic stage. Transmitted by fecal-oral route.

22. Liver Disease Cirrhosis – progressive destruction of the liver Stage 1 Fatty liver. Asymptomatic and reversible. Stage 2 Alcoholic hepatitis. Irreversible. Stage 3 End stage cirrhosis. Liver failure occurs when 80-90% of the liver is destroyed.

23. Liver Disease Liver Cancer – initial signs are mild; diagnosis occurs with advanced stages Hepatocellular Carcinoma Most common primary tumor of the liver Metastatic Liver Cancer Arises from areas served by the hepatic vein

24. Pancreatic Disease Acute Pancreatitis Can be chronic or acute; chronic in 15% of cases Spreads to tissue surrounding the pancreas Very painful; different from pancreatic cancer Results from auto-digestion of tissues around the pancreas due to the premature activation of pancreatic pro-enzymes Precipitating Factors: most common is alcohol; others are biliary tract obstruction, gallstone, or the mumps.

25. Pancreatic Disease Pancreatic Cancer Adenocarcinoma is the most common form Asymptomatic until advanced Metastasizes quickly Mortality rate of 95% Risk factors: smoking, pancreatitis, and dietary factors

26. Lower GI Tract Disorders Celiac Disease Malabsorption syndrome prevents the digestion of gliadin, or the breakdown of gluten. Villi atrophy. Causes: autoimmune disease, defect in intestinal enzyme Appendicitis Obstruction of the appendiceal lumen Wall becomes inflamed as fluid builds in the appendix Symptoms: lower right quadrant rebound tenderness, periumbilical pain Causes: fecalith , gallstones, or foreign object cause obstruction

27. Lower GI Tract Disorders Crohn’s Disease Progressive inflammation and fibrosis cause obstructed areas in the intestine Normally affects the small intestines but may affect any part of the GI tract Inflammation occurs in skip lesions Cause: genetic factor, often occurring during adolescence

28. Lower GI Tract Disorders Ulcerative Colitis Blood and mucous present in the stool Inflammation starts in the rectum and progresses to the colon Cause: genetic factor, often occurring during the 2 nd or 3 rd decade

29. Lower GI Tract Disorders Diverticular Disease Diverticulum An abnormal sac or pouch formed at a weak point in the wall of the alimentary tract Diverticulosis Asymptomatic; outpouching of the mucosa through the muscular layer of the colon Diverticulitis Inflammation of the diverticula; very painful Cause – can be genetic Symptoms – cramping, tenderness, nausea, fever, elevated WBC, and no blood in stool

30. Lower GI Tract Disorders Colorectal Cancer Early diagnosis is essential for good prognosis Second most diagnosed cancer Symptoms: alternating diarrhea/constipation, bleeding, weight loss, anemia, red blood in stool, pain is not typical. Cause: adenomatous polyps are the most common Risk Factors: familial multiple polyps, long-term ulcerative colitis, and increased susceptibility due to low fiber diets

31. Lower GI Tract Disorders Intestinal Obstruction – lack of movement of intestinal contents; most common in the small intestine Mechanical Obstruction Tumors, adhesions Functional Obstruction Impairment of peristalsis Ex. spinal cord injury

32. Lower GI Tract Disorders Peritonitis Inflammation of peritoneal membranes Symptoms: sudden and severe generalized abdominal pain, abdominal distension, dehydration, low blood pressure, tachycardia, and vomiting Chemical Peritonitis Caused by foreign chemical in peritoneal cavity, such as bile or chyme Bacterial Peritonitis Direct trauma affecting the intestines, such as a ruptured appendix or pelvic inflammatory disease

33. Lower GI Tract Disorders Irritable Bowel Syndrome Change in bowel motility associated with affecting the large intestine Causes abdominal cramping and bloating Symptoms must be there 12 weeks out of the year NO BLOOD in stool