Pathophysiology

• Accessory organs of the digestive system

  • Liver
  • Pancreas
  • Gallbladder

  
• Diarrhea


  • Vigorous peristalsis push the contents of the bowel intestine to the large intestine
  • It exceeds the capacity of the large intestine to reabsorb the water
  • May be caused by intestinal infections and food poisoning
  • Anxiety and stress can trigger as well

  
• Constipation


  • Opposite of diarrhea: materials remain too long in the colon and too much water get reabsorbed
  • The result is hard and dry stools that are difficult and uncomfortable to pass
  • High-fiber diet encourages water to enter stool and stimulates intestinal movement, therefore alleviates constipation

  
• Disorders of the esophagus

  • Esophagitis and gastro-esophagus reflux disease (GERD)
  • Esophageal varices
  • Esophageal malignancy
  • Hiatus hernia

  
• Esophagitis and GERD


  • Inflammation in the esophagus causes burning chest pain – heart burns, which may be confused with heart diseases
  • The most common cause: reflux – backflow of stomach juice, known a the gastro-esophagus reflux disease (GERD)
  • GERD is often resulted from incompetent lower esophagus sphincter (LES)

  
• Esophageal varices


  • Development of varicose veins in the esophagus
  • Primary cause: liver cirrhosis increased pressure in veins varicose vein development
  • Danger of hemorrhage
  • Surgical repair reduces risk of bleeding, but liver cirrhosis may cause it develop again

  
• Esophageal cancer


  • Often affects men over 60 in Japan, China, and the Middle East part of Africa
  • Narrows the esophageal lumen and causes dysphagia and vomiting, eventually inability to eat
  • Early metastasis and poor nutritional supply make it one of the cancers with poorest prognosis
• Hiatus hernia


  • Hernia: Part of an organ protrudes through a muscular wall or body opening
  • The esophagus-stomach joint can protrude through the diaphragm
  • Leads to GERD, heart burn, shortness of breath
  • Caused by congenital defect or increased abdomen pressure resulted from obesity

  
• Disorders of the stomach

  • Gastritis
  • Peptic ulcers
  • Gastroenteritis and food poisoning
  • Stomach cancer

  
• Gastritis


  • Acute gastritis: inflammation resulted from agents that stimulate over secretion of acid, which irritates the mucosa
  • Cause: smoking, excessive alcohol, excessive coffee, infection
  • May lead to vomiting of blood
• Chronic atrophic gastritis


  • A degenerative condition where stomach cells do not secret enough acid, leading to poor digestion
  • Another defect is reduced secretion of intrinsic factor – required for absorption of VitB12, may lead to anemia
  • Cause: chronic alcoholism
  • Difference from acute gastritis: reduced acid secretion

  
• Causes of peptic ulcers


  • Infection of Helicobacter pylori
  • Use of non-steroidal anti-inflammation drugs
  • Over secretion of gastric acid

  
• Peptic ulcers


  • Ulcers: lesions of any body surface where necrotic tissue forms as a result of inflammation and shed off, leaving a lesion
  • Stomach -- gastric ulcer; small intestine – duodenal ulcer

  
• Peptic ulcers


  • Damaging factors: pepsin, hydrochloric acid, intestinal fluid (regurgitated through the pyloric sphincter) all can irritate the gastric mucosa and cause inflammation
  • Necrotic tissue then shed off and leave a ulcer lesion
  • About 80% of peptic ulcers are duodenal ulcer, often affecting men between 20 and 50 years old

  
• Helicobacter pylori


  Cause ulcer, inflammation, gastritis and gastric cancer

  
• Complications of peptic ulcers

  • Hemorrhage
  • Hematemesis: bloody vomiting
  • Melana: Blood gets to stool dark color
  • Perforation – break through the gastric or intestinal wall numerous bacteria get into the abdomen peritonitis intense abdominal pain

  
• Gastroenteritis and food poisoning


  • Inflammation of the stomach and intestines, leading to nausea, vomiting and diarrhea
  • Causes: bacteria, virus, chemical toxins, food allergy
  • Stool culture is useful to help decide the causes

  
• Stomach cancer


  • May thicken the stomach wall and lead to obstruction
  • Early symptoms are vague – loss of appetite, heartburn, general stomach distress
  • Hemorrhage and blood vomiting
  • Preserved, cured and salted foods are risk factors

  
• Disorders of the small and large intestines


  • Malabsorption syndrome
  • Inflammatory bowel disease
  • Colorectal cancer

  
• Malabsorption syndrome


  • The inability of the small intestine to absorb nutrients
  • A common form is malabsorption of lipids
  • Often are secondary to obstructions of the pancreatic duct (lack of lipase) or the bile duct (lack of bile)
  • Malabsorption of vitamins also leads to severe problems, e.g. malabsorption of VitK, a essential factor for blood clotting, can lead to increased bleeding tendency

  
• Inflammatory bowel disease


  • Crohn's disease
  • Ulcerative colitis

  
• Crohn's disease


  • Inflammation in colon, sometimes affects the lower segment of the small intestine
  • The thickening of intestinal wall may lead to chronic obstruction
  • Pain; alternating diarrhea, constipation and melana (dark stool due to bleeding); nausea and vomiting; loss of water and electrolytes
  • Cause is unclear. Affect adults aged 20 to 40. Common in Jewish population, rare in black population

  
• Ulcerative colitis


  • Severe inflammation of the colon with extensive ulceration of the colon and rectum. Never affects the lower segment of the small intestine
  • Primarily affect young adults at age 15 to 20
  • Causes: autoimmunity, E. coli infection, hypersensitivity to certain foods
  • Straight and rigid colon – "pipe stem colon"

  
• Colorectal cancer


  • Symptoms vary pending on the location of the tumor: change of bowel habits, diarrhea or constipation, blood appearance in the stool, anemia
  • May lead to obstruction of the lumen
  • Early detection and treatment are essential
• Factors linked to colorectal cancer

  • Familial polyposis: hereditary disease in which numerous polyps, benign lumps of mucosal material, develops in the lumen
  • Diet high in red meat and low in fiber

  
• Functions of the liver


  Liver is the largest glandular organ in our body. It also receives nutrients through the portal vein that collects the blood flow from the rest of

  
• Inflammatory bowel diseases


  • Affect the lower segment of the small intestine
  • Primarily affect young adults at age 15 to 20
  • Causes: autoimmunity, E. coli infection, hypersensitivity to certain foods
  • Straight and rigid colon – "pipe stem colon"

  
• Colorectal cancer


  • Symptoms vary pending on the location of the tumor: change of bowel habits, diarrhea or constipation, blood appearance in the stool, anemia
  • May lead to obstruction of the lumen
  • Early detection and treatment are essential
• Factors linked to colorectal cancer


  • Familial polyposis: hereditary disease in which numerous polyps, benign lumps of mucosal material, develops in the lumen
  • Diet high in red meat and low in fiber

  
• Prevention and early detection of colorectal cancer

  High-fiber diet and population-level screen (every two years for 60-75 years old)
• Liver


  • Largest glandular organ in our body
  • Receives nutrients through the portal vein that collects the blood flow from the rest of the digestive system

  
• Functions of the liver


  • Storage – store the excessive amount of nutrients, e.g. glucose in the form of glycogen
  • Synthesis – various proteins and bile
  • Detoxification – turn toxic substance to harmless or easy-to-expel, e.g. ammonia urea excreted in kidney to urine

  
• Bile


  • Secreted by the liver and stored in the gallbladder
  • Ingredients: water, bill salts, cholesterol and bilirubin (from breakdown of hemoglobin)
  • Emulsify the fat into tiny droplets so that enzymes can digest it
  • Absorption of fatty acid is also important for the absorption of fat-soluble vitamins: such as A, D, E, and K

  
• Diseases of the liver


  • The liver has a amazing capacity to regenerate, but there are diseases that can cause irreversible damage and loss-of-function

  
• Viral hepatitis


  • Hepatitis A
  • Hepatitis B
  • Hepatitis C
  • Hepatitis D
  • Hepatitis E
• Hepatitis A


  • Least serious form resulted from intakes of contaminated water or food
  • Can be prevented through immunization
  • No permanent damage of liver after healing
• Hepatitis B


  • Chronic disease with various severity
  • Transmission: blood or serum transfusion; sexual contact; use of contaminated needles and syringes
  • Immunization works for protection
• Hepatitis C


  • Leading viral cause of chronic liver disease and cirrhosis
  • Transmitted through blood and transfusion
  • ~20% patients develop cirrhosis and need liver transplantation

  
• Hepatitis D


  Can not reproduce in a cell unless hepatitis B virus is also present, therefore is considered a defective virus
• Hepatitis E


  • Transmitted through contaminated water
  • Does not seem to cause chronic disease