(also known as Z-line
or esophagogastric junction
or gastroesophageal junction
) is the anatomical
term for the junction orifice of the stomach
and the esophagus
. At the cardia, the mucosa
of the esophagus transitions into gastric mucosa
The cardia is also the site of the lower esophageal sphincter (LES) (also termed cardiac sphincter, gastroesophageal sphincter, and esophageal sphincter).
Nomenclature and classification
There is disagreement in the academic anatomy community over whether the cardia is part of the stomach, part of the esophagus or a distinct entity, as described in this article. The difference is more than semantic when used in clinical studies and applied to individual patients.
Classical anatomy textbooks, and some other resources, describe the cardia as the first of 4 regions of the stomach. This makes sense histologically because the mucosa of the cardia is the same as that of the stomach.
Many recent writings describe it as the esophageal sphincter.
The stomach generates strong acids
to aid in food digestion
. This digestive mixture is called gastric juice
. The inner lining of the stomach has several mechanisms to resist the effect of gastric juice on itself, but the mucosa of the esophagus does not. The esophagus is normally protected from these acids by a one-way valve mechanism at its junction with the stomach. This one-way valve is called the esophageal sphincter (ES), and prevents gastric juice from flowing back into the esophagus.
During peristalsis, the ES allows the food bolus to pass into the stomach. It prevents chyme, a mixture of bolus, stomach acid, and digestive enzymes, from returning up the esophagus. The ES is aided in the task of keeping the flow of materials in one direction by the diaphragm.
On histological examination, the junction can be identified by the following transition:
However, in Barrett's esophagus, the epithelial distinction may vary, so the histological border may not be identical with the functional border.
The cardiac glands can be seen in this region. They can be distinguished from other stomach glands (fundic glands and pyloric glands) because the glands are shallow and simple tubular.
Deficiencies in the strength or the efficiency of the LES lead to various medical problems involving acid damage on the esophagus.
In achalasia, one of the defects is failure of the LES to relax properly.
Surgical removal of this area is a called a cardiectomy
a term that is also used to describe removal of the Heart
The word comes from the Greek kardia
, the cardiac orifice of the stomach.