Cardia of Stomach

The cardia is the anatomical region of the stomach that marks the transition between the distal esophagus and the gastric body. Although it occupies a relatively small area, it plays a crucial role in the regulation of ingested material entering the stomach and in preventing the backflow of gastric contents into the esophagus. The cardia is sometimes considered a functional zone rather than a sharply demarcated anatomical structure, due to its gradual histological transition.

Structure

Structurally, the cardia lies just distal to the esophageal opening into the stomach. It is characterized by a relatively narrow vertical zone, with the mucosa transitioning from the stratified squamous epithelium of the esophagus to the simple columnar epithelium of the stomach.

The wall of the cardia includes the following layers, consistent with the rest of the gastrointestinal tract:

• Mucosa: Contains mucus-secreting cardiac glands, which differ from the acid-producing glands of the fundus and body. These glands produce protective mucus to lubricate the esophagus and shield it from acid reflux.
• Submucosa: Rich in connective tissue and blood vessels.
• Muscularis externa: Consists of three layers (oblique, circular, longitudinal), though the oblique layer is less developed near the cardia.
• Serosa: Outermost visceral peritoneum covering the stomach.

Histological Features

On a microscopic level, the cardia contains a blend of mucous cells, occasional parietal cells, and basal stem cells. The glands are typically shallow and coiled compared to the deeper glands found in the fundus and body.

Location

The cardia is located at the gastroesophageal junction, where the abdominal esophagus enters the stomach. It is situated:

• Inferior to the diaphragm at the level of the T11 vertebra.
• Posterior to the left lobe of the liver and anterior to the aorta and vertebral column.
• To the right of the fundus and superior to the body of the stomach.

This region includes the lower esophageal sphincter (LES), a physiological (not anatomical) sphincter formed by smooth muscle tone and diaphragmatic crura, crucial for reflux prevention.

Function

The cardia has several key physiological roles:

• Acts as an entryway: It allows the passage of swallowed food and liquids from the esophagus into the stomach.
• Protects the esophagus: The mucus produced here neutralizes any refluxed gastric acid, protecting the lower esophageal mucosa.
• Reflux prevention: Together with the LES and surrounding diaphragm, the cardia helps prevent gastroesophageal reflux during stomach contractions or positional changes.

Clinical Significance

Due to its strategic position, the cardia is involved in several clinical conditions:

• Gastroesophageal reflux disease (GERD): Inadequate function of the LES and cardia can allow acid to enter the esophagus, leading to symptoms like heartburn and esophagitis.
• Barrett’s esophagus: Chronic GERD can lead to metaplastic changes in the epithelium near the cardia, increasing the risk for adenocarcinoma.
• Hiatal hernia: When part of the stomach, including the cardia, herniates through the esophageal hiatus, it can exacerbate reflux symptoms and complicate surgical anatomy.
• Cardia carcinoma: Cancers located at the gastroesophageal junction require careful classification, as treatment protocols differ from distal gastric cancers or esophageal cancers.

Accurate identification of the cardia is essential during upper endoscopy, surgical resection, and imaging, especially when assessing junctional tumors or planning anti-reflux procedures like fundoplication.