What is causing your stomach problems?

Stomach problems can cause pain and embarrassment. Understanding the processes of your stomach can help you keep it healthy. 

How the stomach works

how the stomach works

The stomach is a large, muscular sac situated in the upper left abdomen and separated from the left lung and the heart by the diaphragm. It is divided into two parts: the body (corpus) and the antrum.

The gullet (oesophagus) opens into the corpus, the larger part, but is separated from it by a circular band of muscle called the cardiac sphincter. The antrum is the area of stomach closest to the duodenum, separated from it by the pyloric sphincter. Both sphincters act as one-way valves, ensuring that food passes only in one direction.

The stomach lining contains glands that secrete acidic gastric juices and mucus. The mucus is alkaline and forms a protective barrier that prevents the stomach lining from being damaged by these juices.

Functions of the stomach 

functions of the stomach

The stomach acts as a reservoir for food and can contain up to 1.5 litres (2 1/2 to 3 pints) of it at any one time. This storage facility means that we can eat just a few times a day rather than every half hour or so.

As food enters the corpus the glands in the mucous membrane secrete: hydrochloric acid; a precursor chemical called pepsinogen; and a protein called intrinsic factor, required for the absorption of vitamin B12 in the small intestine.

The hydrochloric acid breaks down foods that are not soluble in water, disinfects the contents of the stomach by destroying bacteria and other micro-organisms and changes pepsinogen into the stomach enzyme pepsin (which breaks down proteins).

The antrum of the stomach releases mucus, dilute sodium bicarbonate (so that the acidic juices are modified before they enter the duodenum) and a hormone called gastrin. The release of pepsin stimulates the muscles of the stomach wall to contract weakly in a wave pattern (peristalsis). This mixes the food thoroughly with the gastric juices, the final mixture being known as chyme.

Stronger peristaltic contractions then pulp the chyme and push it down to the pyloric sphincter. The pyloric sphincter opens with each contraction and allows a small part of chyme through.

What can go wrong?

what can go wrong with the stomach

The complex process of digestion can be affected by imbalances in the gastric juices.

  • Overproduction of gastric juices 
  • If the stomach produces too much gastric juice, the lining of the stomach can become inflamed (gastritis). The condition can be acute, chronic or atrophic (resulting in the loss of the stomach's secretory glands).
  • Underproduction of gastric juices
    Too little gastric juice results in a susceptibility to bacterial infections, such as salmonella and shigellosis.
  • Overproduction of gastrin
    If the stomach releases too much of the hormone gastrin it can result in a duodenal ulcer, heartburn, diarrhoea and steatorrhea (undigested fat in the stools). Causes include a certain type of tumour (a gastrinoma) that secretes gastrin, and a high-protein diet that stimulates gastrin production.
  • Underproduction of gastrin
    Too little gastrin may result from too much fat or too much acid in the chyme. The stomach muscles will be less effective and the time food spends in the stomach will be increased.
  • Gastric ulcer
    Gastric ulcers are a common condition in late middle-age.

 

Cancer of the stomach

cancer of the stomach

Stomach cancer is the sixth most common cancer among adults in the UK. Worldwide, there are marked geographical differences in incidence; high in Japan, for example, but low in the USA. The UK incidence is higher than that of the USA; more than 9700 people are diagnosed with the disease each year.

Nine out of ten of them are aged over 55 and more men than women are affected. Overall, the incidence of stomach cancer has fallen since the 1930s, but the incidence of cancer near the cardiac sphincter has increased. More than 90 percent of stomach cancers start in the glands that produce mucus and gastric juices.

Several risk factors have been identified:

  • Diet 
    Pickled, smoked, barbecued, salty and preserved foods that contain nitrites increase the risk of stomach cancer.
  • Bacteria 
    Helicobacter pylori, a common bacterium that affects many people and is associated with gastric ulcers, is thought to increase the risk three-fold, but it also seems to have a protective effect against cancer around the cardiac sphincter. An infection can be cured by a course of antibiotics.
  • Blood group A:
    There is a statistical link between having this blood group and a higher risk of stomach cancer. This indicates that there may be a genetic predisposition to the disease.
  • Certain medical conditions:
    Pernicious anaemia and atrophic gastritis, which both cause less acid to be produced in the stomach. This may allow more bacteria to survive and it is thought that the nitrite chemicals the bacteria release may cause cancer. Past surgery for a gastric ulcer is also a risk factor. It is thought that this may be because bile juices from the duodenum tend to regurgitate after some types of surgery and irritate the lining of the stomach.
  • Smoking and drinking alcohol:
    Both have been linked to stomach cancer—drinking beer, in particular, increases the risk. Tobacco and alcohol both contain nitrites and other chemicals that irritate the lining of the stomach. 

The symptoms of stomach cancer include: 

  • Indigestion
  • Stomach acidity and belching
  • Feeling full after eating a small amount, and so losing weight
  • Vomiting
  • Difficulty in swallowing and pain
  • Anaemia and blood in the stools, as a result of bleeding from the tumour
  • A high risk of a deep vein thrombosis (DVT)

In all but the most advanced stages, treatment is gastrectomy—removal of the stomach—followed by chemotherapy. If the cancer has spread and is at an advanced stage then treatment is palliative and aimed at relieving symptoms.

Stomach muscles and lining

stomach muscles and lining

Contractions of the stomach's muscular walls churn and thoroughly mix any food arriving there with the strong digestive juices secreted by its lining.

These include:

  • Mucosa Acid
    Digestive enzymes and mucus are secreted by the mucosa, or folded lining of the stomach.
  • Duodenum
    Partly digested food from the stomach passes via a one-way valve into the duodenum, or upper part of the small intestine.
  • Antrum
    Alkaline secretions in the lower part of the stomach, or antrum, neutralize acid in the digested food before it enters the intestine.
  • Oesophagus
    Food from the mouth travels down the oesophagus to the stomach.
  • Vagus nerve
    Muscles in the stomach wall are controlled by the vagus nerve.
  • Smooth muscle
    Layers of smooth muscle fibres allow the stomach to churn food around.
  • Corpus
    In the corpus, or main upper area of the stomach, acidic gastric juices begin the digestive process.

 

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