Overview
This lecture covers the pathophysiology of gastroesophageal reflux disease (GERD), including definition, anatomy, causative factors, complications, morphology, and clinical features.
Definition of GERD
- GERD is a set of symptoms and/or esophageal injuries caused by the passage of stomach contents into the esophagus.
- It results from the movement of acidic gastric contents upwards into the esophageal region.
Anatomy and Physiology of the Esophagus
- The esophagus is a hollow organ, 18–26 cm long, connecting the pharynx to the stomach.
- Its two main functions are food transport and prevention of reflux.
- Esophageal peristalsis enables food movement to the stomach.
- The upper esophageal sphincter prevents air entry and pharyngeal reflux.
- The lower esophageal sphincter (LES) prevents gastric reflux and opens during swallowing.
- Esophagus has four layers: mucosa (produces mucus for lubrication/protection), submucosa, muscularis, and adventitia.
Pathophysiology of GERD
- GERD is due to an imbalance between defensive and aggressive factors in the esophagus.
- Defensive factors: antireflux barrier (mainly LES), esophageal clearance, mucosal resistance.
- Main alterations include LES hypotonia (reduced muscle tone/pressure) and prolonged transient relaxation (>10 seconds).
- Causes of LES dysfunction: muscle-relaxing substances (alcohol, tobacco), obesity, hernia, delayed gastric emptying, and posture changes.
- Impaired esophageal clearance due to abnormal peristalsis or reduced saliva increases damage risk.
- Aggressive factors: acidic gastric content, pepsin, and rarely bile salts.
Complications of GERD
- Barrett's esophagus: squamous epithelium is replaced by columnar (intestinal) epithelium—an adaptive, but risky, metaplasia.
- Peptic stricture: narrowing of the esophagus due to chronic inflammation and scarring.
- Esophageal ulcer: mucosal erosion and bleeding from persistent acid exposure.
Morphology of GERD
- Early GERD may show no histological changes.
- Reflux esophagitis: increased eosinophils in the mucosa.
- Barrett's esophagus: visible replacement of normal squamous cells with columnar cells.
Clinical Manifestations
- Typical symptoms: heartburn (burning in upper abdomen/chest), regurgitation (acid rising to mouth).
- Atypical esophageal symptoms: dysphagia (difficulty swallowing), chest pain, odynophagia (pain on swallowing).
- Extra-esophageal symptoms: laryngitis/pharyngitis, chronic cough, dental erosion.
Key Terms & Definitions
- GERD — A disorder where stomach acid flows back into the esophagus, causing symptoms or injury.
- Lower Esophageal Sphincter (LES) — A muscular ring that regulates flow between the esophagus and stomach, preventing reflux.
- Peristalsis — Coordinated muscle contractions that move food through the digestive tract.
- Barrett's Esophagus — A condition where esophageal lining changes from squamous to columnar due to chronic acid exposure.
- Esophageal Clearance — Mechanisms that remove or neutralize refluxed gastric contents from the esophagus.
- Hypotonia — Lower-than-normal muscle tone or pressure.
Action Items / Next Steps
- Review textbook sections on esophageal anatomy, physiology, and GERD pathophysiology.
- Prepare notes on GERD complications and symptoms for upcoming quiz.