Study Notes on Human Diseases: A Systemic Approach - Gastrointestinal System

Describe the normal structure and function of the digestive tract.
Describe the key characteristics of major diseases of the digestive tract.
Name the diagnostic tests for diseases of the digestive tract.
Explain the etiology of gastrointestinal diseases.
Describe the treatment options for diseases of the digestive tract.
Describe the normal structure and function of the liver, gallbladder, and pancreas.
Explain the etiology of liver, gallbladder, and pancreas diseases.
Describe the treatment options for diseases of the liver, gallbladder, and pancreas.
Describe age-related diseases of the digestive system.

Digestive Tract: Includes
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small Intestine
- Large Intestine
Accessory Organs: Includes
- Liver
- Gallbladder
- Pancreas

Mouth: Ingestion and initial digestion.
Pharynx: Passageway for food to esophagus.
Esophagus: Conduit for food to stomach, aided by sphincter muscle to prevent reflux.
Stomach: Secretes gastric juices to aid digestion, forming chyme.
Small Intestine: Site of most digestion and absorption, includes:
- Duodenum: Receives bile for fat emulsification.
Peristalsis: Muscle contractions that move food through digestive tract.
Large Intestine (Colon): Responsible for water absorption and feces formation.

Liver: Only organ with a double blood supply:
- 30% from hepatic artery (branch of the aorta).
- 70% from portal vein which carries venous blood from the stomach, intestines, pancreas, and spleen.
Functions of the Liver:
- Metabolism of free fatty acids and glucose.
- Storage of glycogen, iron, and fat-soluble vitamins.
- Synthesis of proteins and coagulation factors.
- Detoxification and excretion of harmful substances.
- Production and excretion of bile.

Composed of lobules surrounding a central vein.
Hepatocytes: Liver cells forming plates that radiate from the central vein.
Hepatic Sinusoids: Spaces between hepatocyte plates.
Portal Triads: Contain branches of the hepatic artery, portal vein, and bile duct.

Ascites: Accumulation of fluid in the peritoneal cavity, often due to severe liver disease.
Encephalopathy: Disease affecting brain function.
Coagulopathy: Impairment of blood clotting ability.
Hepatomegaly: Enlargement of the liver.
Mallory Bodies: Cytoplasmic inclusions in hepatocytes that stain pink.

Bile produced by liver, stored in the gallbladder, and released into duodenum for fat digestion.
Bile Composition: Aids emulsification of fats enabling lipase activity.
Bilirubin: Product of hemoglobin breakdown, removed from blood by hepatocytes and secreted into bile.
80-95% of secreted bile reabsorbed in the ileum and returned to the liver.

Oral Inflammation and Infection: Often viral (e.g., canker sores, herpes simplex).
Cancer of the Mouth: Tumors and lesions affecting oral cavity.

Dysphagia: Difficulty swallowing.
Cancer of the Esophagus: Malignant tumors in the esophagus.
Esophageal Varices: Abnormally dilated veins in the esophagus due to portal hypertension.
Esophagitis and GERD: Inflammation and gastroesophageal reflux disease caused by reflux through the cardiac sphincter.
Hiatal Hernia: Protrusion of stomach into the thoracic cavity through the diaphragm.

Gastritis: Inflammation of the stomach lining.
Chronic Atrophic Gastritis: Chronic inflammation leading to tissue damage.
Peptic Ulcers: Sore on stomach lining often caused by:
- $H. pylori$
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- Genetic factors.

Types:
- Peptic Ulcers: General term for ulcers in stomach or small intestine.
- Gastric Ulcers: Ulcers in stomach.
- Duodenal Ulcers: Ulcers in the duodenum.
Hemorrhage: May lead to:
- Hematemesis: Vomiting blood.
- Melena: Black stool indicating gastrointestinal bleeding.
Perforation: Ulcer that has put a hole in the stomach.
Peritonitis: Inflammation of the peritoneum often secondary to perforation.

$H. pylori$ : Exceptionally acid-resistant bacterium, causing ulcers by producing urease to increase stomach pH.
Transmitted among family members, often requiring treatment with acid reducers and antibiotics.

Categories:
- Fatty Liver: Accumulation of fat in the liver.
- Alcoholic Hepatitis: Inflammation due to alcohol consumption.
- Cirrhosis: Late-stage liver disease.
Complications include:
- Jaundice
- Hypoalbuminemia
- Ascites
- Varices.
Prevalence varies due to genetic and environmental factors.
Not all heavy drinkers develop liver disease.

Genetic disorder affecting salt transport in cells leading to thick mucus in lungs and pancreas.
Average life expectancy is around 37 years.
No cure; treatment focuses on symptom management.

Pancreatitis: Inflammation of the pancreas; can be acute or chronic.
- Symptoms: Severe abdominal pain, tenderness, back pain, fever, nausea.
- Caused by premature activation of digestive enzymes within the pancreas.
- Diagnosis typically involves elevated blood amylase levels.

Management includes abstinence from alcohol for liver disease, nutritional support, and in some cases, surgery or transplantation.
Screening and Vaccination: Regular screening for liver diseases and vaccinations for hepatitis B recommended.

Common diseases affecting the mouth, esophagus, gastrointestinal tract, liver, gallbladder, and pancreas.

Content adapted from the textbook "Human Diseases: A Systemic Approach, 8/e" by Zelman, Raymond, Holdaway, Dafnis, Mulvihill.