Cardia

This article is about the cardia in the human body. For the city in Greece, see Cardia (Thrace).

The cardia (or esophagogastric junction^[1][2] or gastroesophageal junction^[3][4][5][6]) 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)^[7][8][9] (also termed cardiac sphincter^[10], gastroesophageal sphincter^[11], and esophageal sphincter^[12]).

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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^[13][14], 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 LES.

Function

The stomach generates strong acids and enzymes 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 lower esophageal sphincter (LES), and prevents gastric juice from flowing back into the esophagus.

During peristalsis, the LES 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 LES is aided in the task of keeping the flow of materials in one direction by the diaphragm.

Histology

On histological examination, the junction can be identified by the following transition:^[15][16]

• nonkeratinized stratified squamous epithelium in the esophagus
• simple columnar epithelium in the stomach

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.

Pathology

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.

Etymology

The word comes from the Greek kardia meaning heart, the cardiac orifice of the stomach.

Additional images

References

1. ^ esophagogastric+junction at eMedicine Dictionary
2. ^ j_02/12465956 at Dorland's Medical Dictionary
3. ^ MedEd at Loyola Radio/curriculum/GI/Image105b.jpg
4. ^ http://cellbio.utmb.edu/microanatomy/digestive/Esophagus.htm
5. ^ http://www.cancer.org/docroot/cri/content/cri_2_4_1x_what_is_esophagus_cancer_12.asp?sitearea=cri
6. ^ http://www.cancer.gov/Templates/db_alpha.aspx?CdrID=302458
7. ^ http://hopkins-gi.nts.jhu.edu/pages/latin/templates/index.cfm?pg=disease1&organ=1&disease=13&lang_id=1
8. ^ http://www.physio.unr.edu/ICC/gallery/LES-1.htm
9. ^ med/2965 at eMedicine
10. ^ cardiac+sphincter at eMedicine Dictionary
11. ^ s_18/12748540 at Dorland's Medical Dictionary
12. ^ http://www.mcg.edu/Otolaryngology/patientGERD.htm
13. ^ c_10/12214493 at Dorland's Medical Dictionary
14. ^ SUNY Labs 37:06-0103 - "Abdominal Cavity: The Stomach"
15. ^ Histology at BU 11101loa
16. ^ Histology at BU 11111ooa