The stomach: everything you need to know about the vital organ you can live without
- The human stomach is the size of a palm and can distend to many times its original size
- Find out about how it works, potential problems and how to keep your gut healthy and happy
The human stomach is surprisingly small when it’s empty, “about the size of a person’s palm”, says Dr Paul Ng, a Hong Kong-based specialist in gastroenterology and hepatology.
Yet as everyone with a good appetite knows, the stomach is elastic and can expand to many times that size. “There are two openings in the stomach” Ng explains. “Sometimes when there is a blockage at the lower opening (pylorus), gastric outlet obstruction (GOO) can occur, in which the stomach becomes extremely distended. Even when that happens, people would vomit instead of having their stomach torn apart by the accumulation, so the stomach doesn’t explode”.
People who say they have a large appetite or they are overweight because they have a large stomach are deluding themselves. Once a person is an adult, the stomach doesn’t change in size. “The intrinsic structure of the stomach is the same for both sexes,” says Ng. “But because males tend to have stronger abdominal wall muscles (the effect of testosterone), the male stomach is more securely placed in the belly. The motility (movement) of the stomach tends to be slower in females due to hormonal effects.” Slow gastric motility can give rise to discomfort or nausea.
Stomach size doesn’t govern what we eat – appetite and cravings do; some people feel full sooner, so they eat less. Stomach rumbling – or to identify it properly ‘borborygmus’ – is normal, it is produced by the movement of fluid and gas in the intestines.
Once swallowed, food takes about seven seconds to get to the stomach. A ball of food is called a bolus while in the oesophagus and upper gastrointestinal tract, and chyme when it’s in the stomach. Smooth muscle tissue contracts in sequence to produce a peristaltic wave to help move the food through the digestive process. The stomach is where food is broken down – partly by the stomach’s mechanical action which grinds food to a paste. This grinding is assisted by gastric acid which is produced in large quantities – about three litres a day.
The acid is necessary to break down what we ingest, it’s also helpful in fighting infection as it helps to kill off bugs that might enter the stomach.
The gastric acid includes industrial-strength hydrochloric acid, which could seriously damage human skin. So the stomach produces large quantities of mucous to cover and protect the stomach’s millimetre thick lining, or mucosa.
Food is only in the stomach for two to five or six hours before it’s sufficiently broken down to pass along the line to the intestines.
During what is called a total gastrectomy, surgeons remove the stomach and directly attach the oesophagus to the small intestine. Some animals, including sea horses and platypuses, have no stomach. Ruminants, cows for example, have four stomachs, to help break down the cellulose in their diet.
Many people know the pain and discomfort of stomach – or peptic – ulcers. These are lesions that develop on the lining of the stomach affecting about 50 million Americans each year. Stress, spicy foods and all that stomach acid were believed to be the cause of stomach ulcers and this belief held for over a century.
Asians usually present with gastric ulcer symptoms a decade earlier than Caucasians. Researchers believe this may be attributable to an H. pylori infection at a younger age. Because the infection can now be treated, ulcers are far better managed today.
While stomach cancer has traditionally been considered a condition that affects older patients, Travis Grotz, a Mayo Clinic surgical oncologist, says that is changing. “The incidence of gastric cancer in the elderly is decreasing,” he explains. “This is likely due to public health efforts to decrease classic risk factors such as smoking, smoked meats and the treatment of H.pylori.”
On the other hand, “we are seeing an increase in the incidence of young patients developing gastric cancer,” he says. “This worrisome trend is occurring across both genders and all races.”
This could be in part because some younger patients have a specific genetic type of cancer that is more aggressive and resistant to treatment, he says. There is also evidence to suggest obesity may be a risk factor for the increased incidence of gastric cancer in the young, he adds.
There are positive advances in medical technology that will continue to help doctors diagnose stomach problems, says Paul Ng. These include advanced endoscopy to diagnose (EUS, for endoscopic ultrasound) and cut out tumours (ESD, for endoscopic submucosal dissection), and burn off precancerous cells (RFA, for radiofrequency ablation). There are even diagnostic electronic capsules – which you swallow, of course – to determine stomach motility and acid reflux, he says.
