Mouth of the Stomach
The cardia ventriculi or pars cardiaca, also known as cardia, is the area of the stomach in which the two-layer oesophagus muscles merge into the three-layer stomach muscles. It is also called the lower esophageal sphincter (lower sphincter muscle of the esophagus) or stomach mouth and represents the entrance area of the stomach.
After the closure of the Cardia after the passage of the bolus (″Bissen″) the swallowing is finished. If the occlusive function is inadequate (so-called cardia insufficiency), the gastric pulp or gastric acid can flow back from the stomach into the oesophagus (so-called "gastroesophageal reflux"). One possible consequence is reflux disease, which can lead to reflux esophagitis (inflammation of the esophagus) in about ten percent of those affected. If the lower esophageal sphincter cannot be opened sufficiently, this is called achalasia.
On the other hand, a brief opening of the cardia allows burping and vomiting. In the case of overweight, an actually sufficient state of tension of the sphincter muscle due to the increased intrabdominal pressure can lead to its opening, especially when lying down.