Gi sem2 Pathology — Past Paper OmpathStudy

1. List the congenital anomalies found in the gastrointestinal tract (10 marks) Answer: Esophageal atresia and tracheoesophageal fistula Pyloric stenosis Duodenal atresia Annular pancreas Meckel's diverticulum Omphalocele Gastroschisis Hirschsprung's disease (congenital aganglionic megacolon) Imperforate anus Malrotation of the intestine 2. List the unique macroscopic and microscopic morphological features of the following diagnoses. a. Boerhaave syndrome (1 mark) Answer: Macroscopic: Full-thickness tear in the esophageal wall, typically in the distal esophagus, leading to mediastinitis. Microscopic: Necrosis and inflammation extending through all layers of the esophageal wall. b. Barrett oesophagus (3 marks) Answer: Macroscopic: Red, velvety mucosa extending proximally from the gastroesophageal junction, replacing the normal pale, squamous esophageal epithelium. Microscopic: Metaplastic columnar epithelium with goblet cells (intestinal metaplasia) replacing the normal stratified squamous epithelium of the esophagus. Dysplasia may also be present. 3. Give a brief outline of the virulence factors linked to Helicobacter pylori implicated in the pathogenesis of chronic gastritis (8 marks) Answer: Urease: Converts urea to ammonia and carbon dioxide, creating an alkaline microenvironment that protects the bacteria from gastric acid. Flagella: Allows the bacteria to be motile and burrow into the gastric mucus layer. Adhesins: Outer membrane proteins (e.g., BabA, SabA) that mediate adherence to gastric epithelial cells. Vacuolating cytotoxin A (VacA): Induces vacuolation in host cells, disrupts tight junctions, and can cause apoptosis. Cytotoxin-associated gene A (CagA): Injected into host cells via a type IV secretion system, it interferes with cell signaling pathways, promotes inflammation, and is associated with increased risk of gastric cancer. Lipopolysaccharide (LPS): A component of the outer membrane that contributes to inflammation and immune evasion. Outer inflammatory protein A (OipA): Induces inflammation and promotes gastric cancer development. Heat shock proteins (Hsp): Involved in bacterial survival and can elicit immune responses. 4. Briefly outline four (4) different mechanisms through which intestinal obstruction occurs (8 marks) Answer: Mechanical obstruction (intraluminal/mural): Physical blockage of the lumen by foreign bodies, gallstones, strictures (e.g., due to inflammation or ischemia), tumors, or intussusception. Extrinsic compression: Obstruction caused by external pressure on the bowel, such as from adhesions (post-surgical), hernias (incarcerated bowel), volvulus (twisting of the bowel), or masses. Functional obstruction (paralytic ileus): Impaired peristalsis without a physical blockage, often due to abdominal surgery, peritonitis, electrolyte imbalances, or certain medications. Vascular obstruction: Ischemia of the bowel wall leading to loss of peristalsis and potential necrosis, caused by conditions like mesenteric artery thrombosis or embolism.