Cardia: Structure, Function & Diseases

The cardia represents the transition area from the esophagus to the stomach. Its opening and closing after the passage of the food pulp completes the act of swallowing. Common reflux disease is caused by cardia insufficiency.

What is the cardia?

The cardia, as the transition area from the esophagus to the stomach, is the Germanized term of cardia. It is actually scientifically referred to as the pars cardiaca ventriculi. The cardia represents the area of the stomach where the two-layered musculature of the esophagus joins the three-layered gastric musculature. However, there is no agreement in the scientific literature regarding the nomenclature and affiliation of the cardia. Classical anatomy considers the cardia as the upper part of the stomach. However, in many clinical publications, it is also referred to as the lower esophageal sphincter (also called the UES) and thus considered part of the esophagus. Other authors present it as a separate structure. Thus, when describing it, the question sometimes arises as to what is actually meant. Regardless of these ways of looking at it, however, the same area, i.e., the transition from the esophagus to the stomach, is usually meant.

Anatomy and structure

As mentioned earlier, in the region of the cardia, the two-layered musculature of the esophagus transitions into the three-layered musculature of the stomach. This sharp transition represents the muscular basis of the cardia as a functional unit. In contrast, the transition from the squamous epithelium of the esophagus to the cylindrical epithelium of the stomach is smooth. Histologically, the esophagus has multiple layers of squamous epithelium, whereas the cylinder epithelium of the stomach is single-layered. The cardiac glands, a subgroup of the gastric glands, are located in this transitional area. Significantly, however, the cardiac glands in many mammals have no relationship to the entrance of the stomach. Their function is to protect the areas of the upper stomach and lower esophagus from aggressive gastric acid. In doing so, they produce mucus with which they line these areas. Spiral-shaped muscle loops run between the esophagus and the stomach, and their contraction is intended to prevent backflow of the food pulp. When the cardia opens briefly, burping and vomiting are induced.

Function and tasks

The function of the cardia is to transport the food pulp from the esophagus to the stomach without causing reflux. The act of swallowing consists of opening the cardia before and closing it after the passage of the food pulp. It also ensures that the aggressive gastric acid cannot flow back into the esophagus. This mechanism works on the basis of the change in the state of tension (tone) of the cardia due to external influences. For example, tone is increased by higher PH (less stomach acid) and higher protein content in the diet. High-fat meals, various medications and certain stimulants, such as nicotine, alcohol and coffee, lead to a decrease in tone. A long-term high-fat diet or stimulant abuse can therefore lead to chronic weakening of the sphincter between the esophagus and stomach. Both long-term and short-term disturbances in the function of the cardia trigger vomiting, belching, and heartburn.

Diseases

In connection with the function of the cardia, the so-called reflux disease should be mentioned. In reflux disease, there is increased reflux of acidic stomach contents into the esophagus. Lifestyle has a great influence on the development of this disease. Thus, in industrialized countries, 10 to 20 percent of the population suffers from reflux disease. It is known that the tone of the cardia is reduced when eating fatty foods and when drinking coffee, alcohol and cigarettes. In the long run, this causes the sphincter between the esophagus and the stomach to slacken. This leads to a so-called cardia insufficiency (weakness of the cardia). The result is constant heartburn. Especially when lying down or bending over, the cardia can no longer close completely. If this condition persists for a longer period of time, it can lead to painful inflammation of the esophageal mucosa due to the influence of aggressive stomach acid. In some cases, these chronic inflammations even develop into esophageal cancer. In reflux disease, a distinction is made between primary and secondary forms.In primary reflux disease, there is weakness of the cardia that is not triggered by other physical changes. Secondary forms are a result of underlying diseases or physical changes. These may be other diseases of the digestive system, anatomical changes of the stomach or esophagus, or pregnancy. Treatment of reflux esophagitis is usually medicinal. In stubborn cases, surgery is sometimes necessary. In the long term, a change in lifestyle has a positive effect on primary reflux disease. There should be a change in diet to a more protein-rich diet. It is also advisable to limit the consumption of stimulants. If other diseases are present, it is a priority to treat them first. In contrast to reflux disease, however, there may also be a disorder called achalasia. In achalasia, the cardia is under constant tension and opens only irregularly. The food pulp can no longer pass sufficiently into the stomach and is transported back into the mouth. In untreated cases, malnutrition occurs with significant weight loss. Achalasia also has primary and secondary forms. The cause of primary achalasia is still largely unclear. Secondary forms are due to damage to esophageal neurons from carcinomas in the cardiac region, from bronchial carcinomas, or from Chagas disease (infection with Trypanosoma cruzi).

Typical and common diseases

  • Reflux disease
  • Esophageal cancer
  • Reflux esophagitis
  • Achalasia