Cardia
Encyclopedia
The cardia is the anatomical
term for the part of the stomach
attached to the esophagus
. The cardia begins immediately distal to the z-line
of the gastroesophageal junction, where the squamous epithelium
of the esophagus
gives way to the columnar epithelium of the gastrointestinal tract.
Just proximal to the cardia at the gastroesophageal (GE) junction is the anatomically indistinct but physiologically demonstrable lower esophageal sphincter. The area termed the cardia overlaps with the lower esophageal sphincter; however, by definition, the cardia does not contain the lower esophageal sphincter. Although the topic was previously disputed, current consensus affirms the cardia is indeed part of the stomach.
The cardia overlaps with but specifically does not contain the lower esophageal sphincter (LES) (also termed cardiac sphincter, gastroesophageal sphincter, and esophageal sphincter). This is in contrast to the "upper esophageal sphincter
" contained in the hypopharynx (area extending from the base of the tongue to the cricoid cartilage) and consists of striated muscle controlled by somatic innervation.
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.
s and enzyme
s 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 this, along with the angle of His
formed here, 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 enzyme
s, from returning up the esophagus. The ES is aided in the task of keeping the flow of materials in one direction by the diaphragm.
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.
In achalasia
, one of the defects is failure of the LES to relax properly.
Surgical removal of this area is a called a "cardiactomy". "Cardiectomy" is a term that is also used to describe removal of the heart
.
kardia meaning heart, the cardiac orifice of the stomach.
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
term for the part of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
attached to the esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
. The cardia begins immediately distal to the z-line
Z-line
Z-line can refer to:*the borders that separate and link sarcomeres within a muscle*a ban on a user's IP address for the purposes of blocking their access to Internet Relay Chat. See Z-line....
of the gastroesophageal junction, where the squamous epithelium
Squamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...
of the esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
gives way to the columnar epithelium of the gastrointestinal tract.
Just proximal to the cardia at the gastroesophageal (GE) junction is the anatomically indistinct but physiologically demonstrable lower esophageal sphincter. The area termed the cardia overlaps with the lower esophageal sphincter; however, by definition, the cardia does not contain the lower esophageal sphincter. Although the topic was previously disputed, current consensus affirms the cardia is indeed part of the stomach.
The cardia overlaps with but specifically does not contain the lower esophageal sphincter (LES) (also termed cardiac sphincter, gastroesophageal sphincter, and esophageal sphincter). This is in contrast to the "upper esophageal sphincter
Upper esophageal sphincter
The upper esophageal sphincter refers to the superior portion of the esophagus.Unlike the lower esophageal sphincter, it consists of striated muscle and yet, is not under conscious control. Opening of the UES is triggered by the swallow reflex...
" contained in the hypopharynx (area extending from the base of the tongue to the cricoid cartilage) and consists of striated muscle controlled by somatic innervation.
Nomenclature and classification
There were previously conflicting statements in the academic anatomy community over whether the cardia is part of the stomach, part of the esophagus or a distinct entity. Modern surgical and medical textbooks have agreed that "The gastric cardia is now clearly considered to be part of the stomach."Classical anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
textbooks, and some other resources, describe the cardia as the first of 4 regions of the stomach. This makes sense histologically
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
because the mucosa of the cardia is the same as that of the stomach.
Function
The stomach generates strong acidAcid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
s and enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s to aid in food digestion
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
. 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 this, along with the angle of His
Angle of His
The angle of His is the acute angle created between the cardia at the entrance to the stomach, and the oesophagus. It forms a valve, preventing reflux of duodenal bile, enzymes and stomach acid from entering the oesophagus, where they can cause inflammation. The angle is created by the collar...
formed here, prevents gastric juice from flowing back into the esophagus.
During peristalsis
Peristalsis
Peristalsis is a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube, in an anterograde fashion. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar...
, the ES allows the food bolus
Bolus (digestion)
In digestion, a bolus is a mass of food that has been chewed at the point of swallowing. Once a bolus reaches the stomach, digestion begins....
to pass into the stomach. It prevents chyme
Chyme
Chyme is the semifluid mass of partly digested food expelled by the stomach into the duodenum.Also known as chymus, it is the liquid substance found in the stomach before passing through the pyloric valve and entering the duodenum...
, a mixture of bolus, stomach acid, and digestive enzyme
Digestive enzyme
'Digestive enzymes' are enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption by the body. Digestive enzymes are found in the digestive tract of animals where they aid in the digestion of food as well as inside the cells,...
s, from returning up the esophagus. The ES 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:- nonkeratinized stratified squamous epitheliumStratified squamous epitheliumA stratified squamous epithelium consists of squamous epithelial cells arranged in layers upon a basement membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural integrity...
in the esophagusEsophagusThe esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach... - simple columnar epitheliumSimple columnar epitheliumA simple columnar epithelium is a columnar epithelium that is uni-layered. In humans, a simple columnar epithelium lines most organs of the digestive tract including the stomach, small intestine, and large intestine...
in the stomachStomachThe stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
However, in Barrett's esophagus
Barrett's esophagus
Barrett's esophagus refers to an abnormal change in the cells of the inferior portion of the esophagus. A positive diagnosis generally requires observing specific macroscopic and microscopic changes...
, the epithelial distinction may vary, so the histological border may not be identical with the functional border.
The cardiac glands
Cardiac glands
The cardiac glands of the stomach secrete primarily mucus. They are few in number and occur close to the cardiac orifice where the esophagus joins the stomach.In general, they are more shallow than those in the other parts of the stomach....
can be seen in this region. They can be distinguished from other stomach glands (fundic glands
Fundic glands
The fundus glands are found in the body and fundus of the stomach.They are simple tubes, two or more of which open into a single duct.-Pathology:...
and pyloric glands
Pyloric glands
The pyloric glands are found in the pyloric portion of the stomach.They consist of two or three short closed tubes opening into a common duct or mouth.These tubes are wavy, and are about one-half the length of the duct....
) 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
Achalasia
Achalasia , also known as esophageal achalasia, achalasia cardiae, cardiospasm, and esophageal aperistalsis, is an esophageal motility disorder involving the smooth muscle layer of the esophagus and the lower esophageal sphincter...
, one of the defects is failure of the LES to relax properly.
Removal
Surgical removal of this area is a called a "cardiactomy". "Cardiectomy" is a term that is also used to describe removal of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
.
Etymology
The word comes from the GreekGreek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
kardia meaning heart, the cardiac orifice of the stomach.
See also
- Artificial cardiaArtificial organAn artificial organ is a man-made device that is implanted or integrated into a human to replace a natural organ, for the purpose of restoring a specific function or a group of related functions so the patient may return to as normal a life as possible...
, that can be used to fight, between other diseases, esophageal cancerEsophageal cancerEsophageal cancer is malignancy of the esophagus. There are various subtypes, primarily squamous cell cancer and adenocarcinoma . Squamous cell cancer arises from the cells that line the upper part of the esophagus...
, achalasiaAchalasiaAchalasia , also known as esophageal achalasia, achalasia cardiae, cardiospasm, and esophageal aperistalsis, is an esophageal motility disorder involving the smooth muscle layer of the esophagus and the lower esophageal sphincter...
and gastroesophageal reflux diseaseGastroesophageal reflux diseaseGastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...
. - PylorusPylorusThe pylorus is the region of the stomach that connects to the duodenum . It is divided into two parts:* the pyloric antrum, which connects to the body of the stomach.* the pyloric canal, which connects to the duodenum....