Esophagus: Anatomy, Function and Diseases

What is the Esophagus?

The esophagus, commonly referred to as the gullet, is a muscular hollow tube that connects the throat (pharynx) to the stomach. In adults, it is approximately 25 to 30 centimeters long and runs behind the trachea (windpipe) through the chest cavity into the abdominal cavity, where it meets the stomach at a junction known as the gastroesophageal junction (cardia). The esophagus is an essential part of the gastrointestinal tract.

Anatomy and Structure

The wall of the esophagus is composed of several layers:

• Mucosa (mucous membrane): The innermost layer, lined with stratified squamous epithelium that protects the esophagus from mechanical stress during swallowing.
• Submucosa: A layer of connective tissue containing blood vessels, nerves, and glands.
• Muscularis propria: A muscle layer consisting of an inner circular and an outer longitudinal muscle layer. The upper third contains striated (voluntary) muscle, while the lower third contains smooth (involuntary) muscle.
• Adventitia: The outermost connective tissue layer that anchors the esophagus to surrounding structures.

At both ends of the esophagus are sphincters: the upper esophageal sphincter (UES) at the junction between the pharynx and esophagus, and the lower esophageal sphincter (LES) at the transition to the stomach. The LES plays a critical role in preventing the backflow of stomach contents into the esophagus.

Function of the Esophagus

The primary function of the esophagus is to transport food and liquids from the mouth to the stomach. This process, known as swallowing (deglutition), occurs in three phases:

• Oral phase: The food bolus is pushed toward the pharynx by the tongue and palate.
• Pharyngeal phase: A reflex closes the airways while the upper esophageal sphincter opens to allow the bolus to enter the esophagus.
• Esophageal phase: Wave-like muscle contractions called peristalsis propel the bolus down through the esophagus and into the stomach.

Common Diseases of the Esophagus

Gastroesophageal Reflux Disease (GERD)

Gastroesophageal reflux disease (GERD) occurs when the lower esophageal sphincter does not close properly, allowing acidic stomach contents to flow back into the esophagus. This causes heartburn, acid regurgitation, and can lead to long-term mucosal damage if left untreated.

Esophagitis

Esophagitis is an inflammation of the esophageal lining, most commonly caused by acid reflux, infections (such as Candida or herpes), or certain medications. It typically presents with painful swallowing and difficulty swallowing (dysphagia).

Barrett Esophagus

In Barrett esophagus, the normal squamous epithelium of the lower esophagus is replaced by columnar (glandular) epithelium as a result of chronic acid exposure. This change is considered a precancerous condition and requires regular endoscopic surveillance.

Esophageal Cancer

Esophageal cancer is a malignant tumor of the esophagus. The two main types are squamous cell carcinoma (more common in the upper and middle third) and adenocarcinoma (more common in the lower third, often arising from Barrett esophagus). Symptoms include progressive difficulty swallowing, unintentional weight loss, and chest pain.

Achalasia

Achalasia is a neuromuscular disorder in which the lower esophageal sphincter fails to relax properly and normal peristalsis is impaired. Patients typically experience progressive difficulty swallowing both solids and liquids, as well as regurgitation of undigested food.

Esophageal Varices

Esophageal varices are enlarged veins in the wall of the esophagus, most commonly caused by portal hypertension due to liver cirrhosis. These dilated vessels are prone to rupture and bleeding, which can be life-threatening and requires immediate medical attention.

Diagnosis

Several diagnostic methods are available for evaluating the esophagus:

• Esophagogastroduodenoscopy (EGD): An endoscopic procedure that allows direct visualization of the esophagus, stomach, and duodenum; tissue biopsies can be taken during the procedure.
• Barium swallow (esophagram): An X-ray examination using contrast dye to assess the shape, lining, and function of the esophagus.
• Esophageal manometry: A test that measures pressure within the esophagus to evaluate motility and sphincter function.
• pH monitoring and impedance testing: Long-term measurement of acid levels and reflux episodes within the esophagus.
• CT scan and endoscopic ultrasound (EUS): Imaging techniques used to assess tumors and nearby structures.

Treatment of Esophageal Conditions

Treatment depends on the specific condition:

• Medical therapy: Proton pump inhibitors (PPIs) for reflux and esophagitis, antifungals or antivirals for infectious esophagitis.
• Endoscopic treatment: Dilation for strictures, variceal banding or sclerotherapy, endoscopic resection of early-stage cancers or Barrett tissue.
• Surgery: Esophagectomy for cancer, surgical myotomy for achalasia, or fundoplication for severe reflux disease.
• Lifestyle modifications: Dietary changes, weight loss, quitting smoking, and reducing alcohol intake can significantly improve symptoms and help prevent esophageal disease.

References

1. Kasper DL et al. - Harrison's Principles of Internal Medicine, 20th edition, McGraw-Hill Education, 2018.
2. Katz PO, Dunbar KB, Schnoll-Sussman FH et al. - ACG Clinical Guideline for the Diagnosis and Management of Gastroesophageal Reflux Disease. American Journal of Gastroenterology, 2022.
3. World Health Organization (WHO) - International Classification of Diseases (ICD-11), Chapter 13: Diseases of the Digestive System, 2023.