Stomach – structure, function, diseases

Its task is to prepare the food with the help of stomach acid so that it can be optimally absorbed by the intestine. Without the stomach, we would not be able to absorb and process large quantities of food at once. We would have to eat many small meals. The stomach also protects us from infections, as its acidic environment kills pathogens. But it is also susceptible to a variety of stomach ailments and diseases.

The stomach is a tubular and sac-shaped organ. It consists of muscle tissue and is hollow on the inside. The stomach is an important part of our digestive system and is responsible for processing the food we eat. It absorbs the food from the esophagus, mixes and stores it and gradually breaks it down. The stomach then releases the pre-digested chyme in portions into the duodenum. The stomach is about 20 to 30 centimeters long. Depending on age and individual situation, the stomach can hold up to two liters of food and liquid.

Where is the stomach?

The stomach is located in the left upper abdomen. It forms the connection between the esophagus (esophagus) and the duodenum (part of the small intestine). The elastic muscle sac lies directly under the diaphragm. Its lowest point is approximately at the level of the navel.

The stomach has a special anatomy that enables it to store, break down and pre-digest food. It consists of several sections. The stomach structure at a glance:

• Stomach entrance (cardia): At the entrance to the stomach, the esophagus opens into the stomach. The stomach entrance forms the transition between these two organs and has a ring-shaped sphincter (lower esophageal sphincter). This muscle prevents the reflux of stomach contents into the esophagus and protects the sensitive mucous membrane of the esophagus from the aggressive stomach acid.
• The bottom of the stomach (also known as the fundus): The bottom of the stomach adjoins the entrance to the stomach. This curved, upper part of the stomach forms a kind of “dome”. Air often collects in it and enters the stomach when swallowing – visible as a “stomach bubble” on an X-ray. The bottom of the stomach plays an important role as a storage space for the food that enters the stomach. The food remains here and is partially predigested with the help of gastric acid before it enters the stomach (corpus).
• Body of the stomach (corpus ventriculi): The body of the stomach is the largest part of the stomach. It lies between the bottom of the stomach and the stomach outlet. In the stomach, the food is vigorously mixed and broken down by the muscle layers of the stomach. The glands of the stomach lining (mucosa) produce substances that help the stomach to digest and at the same time protect it from the aggressive effects of stomach acid.
• Gastric outlet (also pylorus): The pylorus is the part of the stomach that passes into the small intestine. It regulates the transportation of the stomach contents into the duodenum and ensures that the contents are only passed on in small quantities and in processed form. The pylorus consists of a ring muscle, the pyloric sphincter, which opens and closes in order to pass on the chyme in a controlled manner.
• Gastric mucosa: The gastric mucosa is the inner lining of the stomach. It consists of several layers of epithelial cells. It is moist and has a glandular structure in which specialized cells produce gastric juice. The mucous membrane is about 1 to 2 millimeters thick and forms the surface that protects the stomach from aggressive substances that are released during digestion. It is strongly folded and contains numerous gastric glands.

A well-functioning stomach is crucial for digestion and the health of the body. It prepares the food for further processing in the small intestine, protects the body from harmful microorganisms and controls the digestive process.

Stomach function: The most important tasks of the stomach

• Comminution and mixing of the food: The stomach mechanically comminutes the ingested food through muscle contraction and mixes it with gastric juice to form a pulpy mixture (chyme), the so-called chyme. This facilitates further digestion.
• Production of stomach acid: The stomach produces stomach acid. This consists of hydrochloric acid (HCl), enzymes and mucus. The hydrochloric acid kills pathogens. The enzyme pepsin promotes protein digestion. And the mucus protects the stomach lining from the aggressive acid.
• Intermediate storage of food: The stomach serves as a store that gradually passes the food on to the small intestine. In this way, the digestive tract is not overloaded.
• Control of the transfer of food: The stomach gradually releases the chyme through the pylorus to the small intestine, thus enabling optimal digestion.

How does digestion work?

Digestion begins in the mouth. There the food is crushed and mixed with saliva. In the stomach it is broken down further with the help of gastric acid and enzymes. The main digestion takes place in the small intestine: Here the nutrients are broken down with the help of enzymes from the pancreas and bile acids from the liver and absorbed into the blood. Indigestible residues pass into the large intestine, where water is removed before the remaining waste products are excreted.

Task and function of the gastric mucosa

The gastric mucosa plays a crucial role in the protection and function of the stomach. Your main tasks are:

• Protection against acid: The stomach lining produces a thick layer of mucus that protects the stomach lining from the aggressive stomach acid (hydrochloric acid) that is necessary for digestion. Without this protection, the acid would attack and damage the stomach lining itself.
• Protection against mechanical damage: The mucous membrane also protects the stomach from mechanical damage caused by the movement of the stomach wall during digestion.
• Defense against germs: It also contains the body’s own antibodies that protect against pathogens and germs that could enter the stomach with food.
• Production of digestive enzymes and acids: There are glands in the stomach lining. They produce digestive enzymes (e.g. pepsin) and stomach acid, both of which are necessary for the breakdown of food and the activation of enzymes.

Stomach pain can have various causes. Common causes are

• Digestive disorders: Irregular or excessive food intake, fatty or hard-to-digest foods and eating too quickly can put a strain on the stomach and lead to pain. Too much alcohol or drinks containing caffeine can also irritate the stomach.
• Reflux (heartburn): When stomach acid flows back into the esophagus, it can cause stomach pain and heartburn in the upper abdomen. This often occurs when the lower esophageal sphincter muscle is weak, especially when the stomach passes through the diaphragm and a so-called hiatal hernia (often referred to as a diaphragmatic hernia ) forms.
• Stomach ul cers: Ulcers in the stomach lining cause pain, which can be aggravated by stomach acid or food. They are often caused by an infection with the bacterium Helicobacter pylori or by taking painkillers from the non-steroidal anti-inflammatory drugs (NSAIDs) group.
• Gastritis: Inflammation of the stomach lining due to infection, stress, excessive alcohol consumption or medication can lead to pain.
• Gastric emptying disorders (gastroparesis): If the stomach empties its contents too slowly, e.g. due to impaired muscular activity of the stomach, this can lead to pain and a feeling of fullness, nausea and vomiting.
• Stomach pain during pregnancy: Stomach pain during pregnancy has various causes, which are often interrelated. In the first few months, the hormone balance, in particular the hormone progesterone, can affect the gastrointestinal tract by slowing down stomach movements and leading to indigestion or heartburn. The growing baby exerts pressure on the stomach and surrounding organs, which may lead to gas and bloating. In the later months of pregnancy, this can lead to pain or discomfort in the stomach area.
• Other diseases: In some people, stomach pain is also caused by illnesses such as functional dyspepsia, pancreatitis or liver disease.

The exact cause of stomach pain can usually only be determined by a medical examination and, if necessary, further tests.

People with sensitive stomachs are not the only ones who suffer from a variety of stomach complaints and stomach diseases that have different causes. All stomach diseases can vary in their severity and symptoms. Signs of a stomach disorder include a feeling of pressure in the upper abdomen, nausea, vomiting, loss of appetite and pressure pain in the stomach area. In the event of unusual changes or prolonged symptoms, it is advisable to consult a specialist in gastrointestinal diseases (= gastroenterologist).

Here is an overview of common stomach problems and stomach diseases:

Gastrointestinal infection (gastroenteritis)

A gastrointestinal infection is an inflammation of the stomach and/or intestines, usually caused by an infection with viruses, bacteria or parasites. The most common symptoms are nausea, vomiting, diarrhea, abdominal pain and fever. Common triggers are viruses such as noroviruses or rotaviruses, but bacterial infections (e.g. with salmonella or E. coli) can also be responsible. Gastrointestinal diseases are usually contagious and are transmitted through contaminated food and water or direct contact with infected persons.

Stomach ulcer (ulcus ventriculi)

A peptic ulcer is an open wound in the stomach lining caused by the action of stomach acid. A stomach ulcer can cause pain and discomfort. It should be treated by a doctor. The most common causes are

• Infection with Helicobacter pylori: A bacterium that can damage the stomach lining.
• Use of painkillers: NSAIDs can irritate the mucous membrane and impede healing.
• Excessive alcohol consumption and smoking: Both can damage the stomach lining.
• Stress: Stress can increase the production of stomach acid and damage the mucous membrane.

Inflammation of the stomach lining (gastritis)

Gastritis is an inflammation of the stomach lining. Possible symptoms of gastritis are pain, nausea and indigestion. It can be acute or chronic. The most common causes are

• Infection with Helicobacter pylori: Helicobacter pylori is a bacterium that can damage the stomach lining.
• Medication: Mainly non-steroidal anti-inflammatory drugs (NSAIDs for short) such as ibuprofen
• Alcohol consumption and smoking: These factors irritate the mucous membrane.
• Stress: Can promote the development or worsening of gastritis.
• Autoimmune diseases: Here the immune system attacks its own stomach lining.

Common symptoms of gastritis are:

• Abdominal or stomach pain, often in the upper abdomen
• Nausea and occasional vomiting
• Feeling of fullness or flatulence after eating
• Heartburn or an unpleasant burning sensation in the stomach area
• Loss of appetite
• Digestive disorders

In severe cases, blood may appear in the stool or black stool (tarry stool), which indicates more severe damage to the stomach lining. If you experience these symptoms and they persist, you should consult a doctor to clarify the exact cause and initiate appropriate treatment.

Heartburn and reflux disease

Heartburn is a burning sensation behind the breastbone caused by the reflux of stomach acid into the esophagus. This happens when the lower esophageal sphincter does not function properly and stomach acid enters the esophagus, causing irritation and discomfort. Heartburn often occurs after eating or when lying down.

Reflux disease (also known as gastroesophageal reflux disease or GERD) is a chronic form of heartburn in which stomach acid regularly flows back and causes symptoms such as heartburn, acid regurgitation, coughing and sore throat. In the long term, the disease can damage the esophagus and lead to inflammation(esophagitis) or even to a change in the esophageal cells (Barrett’s esophagus).

Further information on treatments for reflux can be found here:

• Laryngopharyngeal reflux treatment
• Reflux treatment
• Eosinophilic esophagitis treatment

Gastric emptying disorder (gastroparesis)

Gastric emptying disorders are diseases in which the stomach does not empty the chyme into the small intestine properly or too slowly. This leads to symptoms such as bloating, nausea, vomiting, flatulence and abdominal pain. The disorder can be caused by damage to the nerves or muscles in the stomach that are responsible for gastric motility. Possible causes are diabetes, certain medications or illnesses such as gastritis.

Diaphragmatic hernia (diaphragmatic hernia)

A hiatal hernia occurs when part of the stomach protrudes into the chest cavity through a weak point in the diaphragm. The diaphragm is a muscle-tendon structure that normally separates the abdominal cavity from the chest cavity. In the event of a diaphragmatic hernia, parts of the stomach protrude upwards through this opening. This can cause stomach acid to enter the esophagus, which leads to reflux symptoms. These often manifest themselves as heartburn, belching and difficulty swallowing. Sometimes, however, the condition remains asymptomatic, as the hernia itself is usually not noticeable. The risk of developing a diaphragmatic hernia increases with age. Men are more frequently affected than women.

Irritable stomach (functional dyspepsia)

Irritable stomach syndrome is a common stomach disorder that causes recurring symptoms such as stomach pain, bloating, nausea and heartburn – without a clear organic cause such as inflammation or an ulcer. The exact causes are not always clear, but factors such as past gastrointestinal infections, stress, immunological processes in the small intestine, diet, certain medications and/or a hypersensitivity of the stomach to normal digestive processes may play a role. An irritable stomach is often accompanied by other irritable bowel symptoms and usually requires symptomatic treatment. Find out more aboutcomplementary medical treatment for gastrointestinal disorders.

Gastrointestinal stromal tumors (GIST)

Gastrointestinal stromal tumors (GIST) are rare tumors that develop in the gastrointestinal tract. They originate from special cells that control the movement of the muscles in the digestive tract. GIST can be benign (benign) or malignant (malignant), whereby the malignant tumors can spread to other parts of the body.

Common symptoms:

• Abdominal pain
• Feeling of fullness
• Nausea or vomiting
• Blood in the stool or vomit
• Weight loss

GISTs are usually detected by imaging techniques such as CT or MRI and confirmed by a biopsy (tissue biopsy). Treatment can include surgery, radiotherapy and drugs that target the tumor.

Stomach cancer (gastric carcinoma)

People with stomach cancer have a malignant tumor in the stomach that can occur anywhere in the organ. It usually originates from the glandular cells of the gastric mucosa, which are responsible for the production of stomach acid and mucus. Doctors refer to such tumors as adenocarcinomas. The medical term for stomach cancer is gastric carcinoma.

Stomach pain and stomach cramps can disappear on their own in many cases, but there are situations in which it is advisable to consult a doctor. Here are some signs and accompanying symptoms that you should talk to a doctor about:

• Persistent or severe pain: If stomach pain lasts longer than a few days or is very severe.
• Blood in vomit or stool: Bloody vomit or black, tarry stool may indicate a stomach ulcer or other serious illness.
• Weight loss for no apparent reason: A sudden, unexplained weight loss should definitely be checked out by a doctor. The cause may be a serious illness such as cancer or a chronic gastrointestinal disorder.
• Fever and chills: These symptoms may indicate an infection that needs to be treated.
• Difficulty swallowing: Difficulty swallowing or the feeling that food is getting stuck may be a sign of a disease of the esophagus or stomach.
• Severe nausea or vomiting: If you can no longer keep liquid and solid food down, this may indicate a serious illness.
• Pain that spreads: Pain that radiates to the back, chest or other parts of the body can also be a sign of a serious illness such as a heart attack or pancreatitis.
• Sudden, very severe pain: If you suffer from sudden and very severe stomach pain accompanied by nausea, vomiting, fever or a stiff stomach, the cause may be an acute illness such as appendicitis or a gastric rupture. Immediate medical treatment is then absolutely necessary.
• Recurrent or chronic stomach pain: Recurrent or chronic stomach pain can indicate a chronic disease such as reflux disease, gastritis or a stomach ulcer.
• Tiredness and weakness: Malnutrition or digestive problems can lead to persistent tiredness and weakness.

The treatment of stomach complaints and stomach diseases depends on the cause and severity of the complaints. Here are some preventive tips for a healthy stomach:

• Pay attention to a healthy rhythm – too many stress hormones in the blood make the stomach and intestines restless and nervous.
• Consciously take time to eat.
• Chew your food thoroughly – poorly chewed food causes the most problems for the stomach and intestines.
• Only eat as much as your stomach and intestines can process. If you are full of vigor and energy after eating, you have done everything right.
• If you have an irritable stomach, avoid raw vegetables and dairy products as well as excessive fat from midday onwards.
• Only eat easily digestible food in the evening, for example steamed vegetables with some rice, meat or fish.
• Keep an eye on your medication. Many medications cause gastrointestinal complaints.
• Are you wondering why your stomach and intestines are irritated? Then write down what you eat throughout the day for a few days. Also make a note of when which symptoms occurred. Do you notice anything?

Smoking and alcohol damage the stomach lining. Perhaps now is the time to stop smoking and reduce your alcohol consumption.