Stomach: anatomy, how it works, symptoms and problems

How the stomach works

The stomach, located in the upper left part of our abdomen, is that part of the digestive system that connects the esophagus to the intestine. It is connected to the esophagus by the lower esophageal sphincter (or cardiac valve) which prevents food from rising through the esophagus and to the small intestine by a valve called the pyloric sphincter. This, by opening and closing, regulates the emptying of our stomach and keeps digestion going.

Anatomically, the stomach is a sac approximately 25-28 cm long and 10-12 cm wide which can also contain 1000-1500 ml of liquid. We speak of an “over-distended” stomach, of gastrodilation when the organ is not very elastic following a constant excessive intake of food which does not allow the stomach to empty. The so-called “second digestion of food” takes place in the stomach (the first in the mouth) which lasts approximately 5 hours. There are several parts in the stomach:

• The bottom, at the top, is the area where gastric juices are produced. These juices contain many substances such as potassium, the enzyme lipase, pepsin which breaks down proteins into amino acids, bicarbonate which helps reduce acidity, hydrochloric acid which activates pepsin and sterilizes food. And the well-known “Intrinsic Factor” which allows the absorption of vitamin B12 and iron in the intestine;
• The corpus is the central part of the stomach, where food is stored during digestion;
• The pyloric canal is rich in glands that produce mucus that protects the gastric wall from the acids used in the digestion process.

The entire stomach is then covered by some muscles (the tunic) that, by contracting, allow the food present in the body of the stomach to mix. Finally, the stomach is wrapped by the peritoneum, a fibrous structure that protects it and keeps it attached to the abdominal wall and nearby organs.

Stomach ache: why?

Stomach pain is usually a temporary disorder that resolves on its own or with a change in eating habits. However, if the disorder lasts more than a few days, it could be the cause of a more serious condition.

Among the most common and less serious causes of stomach pain are:

• Meteorism, a technical term for air in the stomach;
• Digestive problems following meals that are too large or difficult to digest;
• Cigarette smoking, anxiety and stress or alcohol consumption;
• Taking certain medications, including antibiotics and nonsteroidal anti-inflammatory drugs;
• Rare and distant episodes of gastroesophageal reflux.

Then there are less common but more serious causes. Among these:

• Gastric ulcer. An erosion, similar to a burn, of the lining of the stomach. It can be seen with a gastroscopy;
• Peptic ulcer. In this case the lesion involves the mucosa exposed to gastric juices. It is a subtype of gastric ulcer. If the lesion is so deep that it involves the blood vessels and therefore bleeds, in this case it is said to be perforated;
• Stomach tumors. The stomach is one of the organs most subject to tumors or neoplasms. It is estimated that in Europe approximately 23% of all benign and malignant neoplasms can be traced back to this organ. The factors that favor these problems could be due to diet. Among the bad habits, the AIRC (Italian Association for Cancer Research) indicates the use of too much salt, fats and smoked foods, a diet based on starches. A proven role is also played by helicobacter pylori, a bacterium that can also cause gastric and duodenal ulcers, and by family predisposition;
• Acute gastroenteritis. An inflammation of the mucous membranes of both the stomach and intestines, usually of infectious origin. It is also very common in children under 5 years of age;
• Gastritis. When the inflammation involves only the stomach. It can be due to both an incorrect diet and the intake of drugs, but a bacterial or autoimmune origin must not be excluded. It can develop rapidly and suddenly, and in this case we speak of ACUTE GASTRITIS;
• Hiatal hernia: a balloon that forms in the stomach wall at the level of the hole that connects the stomach to the esophagus;
• Gastroesophageal reflux. Occurs when stomach acid flows back up from the stomach into the esophagus.

Digestion and tachycardia

It often happens to feel “strange” sensations in the stomach, even slight discomforts that are not real pain. For example, after meals it is possible to feel the stomach “pulsing” and the heartbeats resume. Poor digestion, or a massive intake of food that we are not used to, can induce tachycardia. In these cases we speak of “gastro-cardiac syndrome” or “Roemheld syndrome” which has as its trigger the stimulation of the gastrocardiac reflexes, due to an excess of air in the stomach. There is no need to be afraid, the disorder passes, but it is good to be careful to avoid weighing yourself down by eating excessively and foods that are difficult to digest.

The bloated stomach

The sensation of a swollen stomach, which we also perceive as a “hard stomach”, as if it were full of air, is usually called abdominal swelling and is due to an accumulation of gas in the stomach or intestine. It is not always easy to understand whether it is the upper part of the latter or the lower part of the stomach. In some cases it is accompanied by stomach pain and most of the time derives from diet, in particular from carbonated drinks, from having eaten too quickly, but it can also be a physical symptom of a lot of stress. Clearly if the swelling persists or worsens, accompanied by strong abdominal pain and episodes of diarrhea, it is best to consult your doctor.

There are not many things to do. The swelling goes away on its own, but if it happens frequently you can consult a nutritionist to start a diet that reduces foods and drinks that favor the accumulation of gas in the digestive system, such as legumes and vegetables from the cabbage family such as broccoli, Brussels sprouts, cabbage and cauliflower. Even some fruits like apples, pears and peaches, and some whole grains can promote stomach bloating. In other people, milk and its derivatives create problems.

Stomach acidity

Heartburn (medically known as gastric pyrosis), which we often identify as “heartburn,” is a painful burning sensation (ranging from mild discomfort to real stabbing pain) in the upper abdomen. It is often associated with other disorders such as belching and regurgitation (the rising of liquid/food from the stomach to the esophagus, sometimes even into the mouth), which can also cause burning in the throat and oral cavity. It is a symptom that can depend on many different causes. It is very common and can recur several times throughout life, often after particularly stressful events.

What causes heartburn? In general, gastric pyrosis is caused by increased production of acids or by the weakening of the wall of this organ, which is called the gastric mucosa. Its cells in fact produce mucus, a foamy substance that has the function of protecting the digestive system from both acids and external agents. Disturbances in this balance increase stomach acidity, leading to disorders such as gastroesophageal reflux disease (GERD), in which the reflux of stomach acid, which is normally limited and painless, causes pain and potentially more serious complications.

Ulcers and Helicobacter pylori

The so-called ulcer (peptic ulcer) is a roundish lesion of the mucosa of the stomach or duodenum resulting from corrosion by gastric acid or digestive juices. The most frequent symptoms are a shooting, burning or intense pain, usually in the substernal region. The discomfort usually eases with the ingestion of solid foods and tends to appear, last for weeks and disappear frequently. In most cases, stomach ulcers heal without leaving complications, but it is best to see a doctor if the condition persists to avoid:

• Dangerous bleeding (hemorrhage);
• Perforation of the ulcer;
• Stomach obstructions.

Today we know that one of the main causes of ulcers is Helicobacter pylori, a spiral-shaped bacterium that can proliferate in the gastric mucosa, which lines the stomach. Sometimes, but not always, Helicobacter causes, in addition to the pain caused by the ulcer, other symptoms such as nausea, vomiting and loss of appetite. It is best to diagnose Helicobacter (with specific serological tests, breath tests and sometimes endoscopy) and treat it because in the long term, the infection is associated with a 2-6 fold increase in the risk of MALT lymphoma and especially gastric carcinoma. Treatment consists of a therapy based on one or two antibiotics for 1-2 weeks.