The Human Stomach
A Look Inside a Useful but Dispensable Organ

Our digestions . . . going sacredly and silently right, that is the foundation of all poetry . . . the most poetical thing in the world is not being sick.   
-- G. K. Chesterton

magine a churning vat of hot, corrosive acid, so strong that almost anything put into it is attacked and degraded to a foul-smelling "soup" that you would take pains to avoid stepping in if it were on the ground. Occasionally, alas, it is on the ground, having been forcibly expelled from the acid pit that created it - the human stomach. Like it or not (biology is not always pretty), that disgusting stuff is the normal content of our stomachs, where it is called chyme (from the Greek khumos, juice).

In this article we will look at the workings of the stomach, including the role it plays in digestion and the way in which some of the fundamental discoveries about this vital process were made (there are some surprises in store for you). In the accompanying sidebar, we see how one culprit - the bacterium Helicobacter pylori (H. pylori) - has been implicated in some of the worst ills that plague the stomach, and we discuss an age-old but newly rediscovered natural remedy for those ills: mastic.

How can a delicious meal, so steeped in enchanting aromas and flavors, be transformed so quickly into something so vile as chyme? And if the stomach is capable of such chemical mayhem on organic matter, why doesn't it cannibalize us from the inside out, like a black hole devouring the nearby stars?

The answers lie in the composition of the stomach's digestive juices and of its protective lining - a marriage of chemical compounds ideally suited to their opposite tasks. The digestive juices consist mainly of hydrochloric acid - very strong stuff, known as muriatic acid by tradesmen who use it for such purposes as ore reduction, metal pickling, and cleaning the mortar from bricks. About 2 to 3 quarts of it are secreted into the stomach daily by about 35 million glands distributed throughout the stomach wall.

Together with digestive enzymes, mainly pepsin, the acid attacks foodstuffs - mainly proteins, which it converts to smaller units called polypeptides, or even to their ultimate molecular components, amino acids. This process is aided by rhythmic muscular contractions of the stomach wall, which churn things around.

So why is the stomach wall, which itself consists mainly of protein, not turned into chyme as well? Because it has a lining of epithelial cells that secrete a protective layer of mucus (the lining looks like folds of glistening pink velvet) that is impervious to acid and pepsin. As long as this mucous layer remains intact and healthy, the stomach will be too. But if the mucus is compromised in some way, the stomach lining can become irritated or inflamed. The result is gastritis. The most common form of this condition, called nonerosive gastritis, is almost invariably associated with the harmful bacterium H. pylori.1,2

Figure 1. Human anatomy of the upper gastrointestinal tract.

The worst aspect of gastritis is that it can set the stomach up for a far more serious affliction: peptic ulcers (peptic means having to do with digestion). These are lesions, a few millimeters to a few centimeters across, involving some erosion of tissue caused by the gastric juices. They are usually painful, although they can be asymptomatic. They begin when a tear or hole in the structure of the mucous lining breaches its chemical defenses against the acid and pepsin, allowing them to attack the sensitive tissue underneath. If they go deeply enough into that tissue, the ulcer may bleed. In severe cases, the acid may eat all the way through the stomach wall (a perforated ulcer), with life-threatening consequences.

Peptic ulcers are not confined to the stomach. About 80% occur in the upper part of the small intestine, called the duodenum (from the Latin word for twelve, because it is about twelve finger-breadths in length). They also occur, albeit rarely, in the lower esophagus. Stomach (gastric) ulcers tend to be intermittently painful, if at all. They occur most often in the lower part of that organ, the antrum, which necks down to merge with the duodenum. This juncture is actually a sphincter, a ringlike muscle that opens or closes a bodily orifice or passageway as needed.

This particular sphincter is called the pylorus (from the Greek pyloros, gatekeeper). Normally closed, it opens to allow the passage of chyme into the duodenum when the stomach has finished its work. This occurs about 3 to 4 hours after a meal, on average, although some foods - especially fatty ones - tend to remain in the stomach much longer than that. Typically, the pylorus lets the highly acidic chyme through in small squirts, no larger than can be instantly neutralized by the normally slightly alkaline duodenum. If too much acid gets through, it can eat its way into the wall, causing a duodenal ulcer - and nearly constant pain.

The rare esophageal ulcer occurs if stomach acid damages the lower end of the esophagus, as can occur in the condition known as gastroesophageal reflux disease (GERD), more commonly called heartburn. Here too, the problem is a faulty valve, called the cardiac sphincter because of its proximity to the heart. Sometimes it fails to close properly, allowing backflow (reflux) of acid into the esophagus, which has no adequate chemical defense mechanism.

Mark Twain once wrote, "Eat what you want and let the food fight it out inside." Round One takes place in the stomach, a muscular, elastic, roughly J-shaped sac, pink and glossy on the outside, which lies crosswise in the abdominal cavity, beneath the diaphragm. With a holding capacity of 1 to 2 quarts, it connects the esophagus above to the small intestine below. It is but one segment of the alimentary (or digestive, or gastrointestinal) tract - a long, muscular tube that extends from mouth to anus and that is about 15 feet long while we're alive. (When we die it relaxes to about 30 feet because the muscle tone that had kept it functioning is lost.) Every inch of that tube is full of chemical and mechanical activity that continuously transforms its contents while pushing them along their tortuous path. Three other organs secrete substances into the digestive tract, at the duodenum: the liver, the gallbladder, and the pancreas.

A curious fact about the stomach is that, for all its "cast-iron" ability to handle just about anything we feed it - puff pastries to pizzas, sea slugs to salsa - it dislikes most synthetic drugs and is irritated by them. Aspirin, for example, is a notorious stomach irritant because it tends to start pinpoint hemorrhages that, if continually aggravated, can develop into ulcers. Many other over-the-counter drugs, particularly nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, are also implicated, but drugs in general seem to disagree with the stomach, causing a host of unpleasant side effects. This is, of course, all the more reason to seek natural, safe, nonirritating remedies for gastrointestinal disorders. The ideal choice is mastic.

Another curious fact about the stomach is that, although it seems like such a vital organ, it isn't vital at all! It is merely a physiological convenience - a useful but unnecessary food reservoir that allows us to get by on two or three meals a day instead of the six or more we would need without it. Many people have had their stomachs surgically removed because of cancer or some other reason and have lived more or less normally - albeit with altered eating habits and nutritional care - for many years. The small intestine, it seems, can do well enough on its own to sustain us. We will soon see why this is so.

We owe much of what we know about the workings of the stomach to a bizarre accident and the zealousness of one doctor. In 1822, Alexis St. Martin, a 19-year-old French Canadian trapper in northern Michigan, suffered a terrible shotgun wound to his side. He was treated with great care and skill by Dr. William Beaumont, an American army surgeon who had served in the War of 1812. The young man's wound healed - almost - and he enjoyed good health until his death at 82.

In that "almost" lies a fascinating chapter in the history of medicine. Repairing the damage to St. Martin's side proved impossible without leaving an opening (called a fistula), nearly an inch across, that led directly from his stomach to his skin. Through this "window," Dr. Beaumont was able to observe what went on in there, and he took maximum advantage of his unique opportunity. For eight years, he made meticulous observations of stomach processes under many different conditions. He observed, e.g., how different foods and different emotional states of his subject affected the digestive process, and he extracted samples of gastric juice to send all over the world for analysis.

In doing this, however, he so bullied the grateful but hapless St. Martin that the poor fellow eventually ran away. In 1833 Dr. Beaumont published his studies in a book, Physiology of Digestion, that revolutionized medical science. He described no fewer than 238 experiments performed. His work not only vastly enriched our understanding of digestive processes, but it also served to stimulate much further work in the field of gastroenterology, the branch of medicine concerned with the study of disorders affecting the stomach, intestines, and associated organs. And it ensured his place in the pantheon of medicine.

Among those inspired by Dr. Beaumont's research was a young French physiologist, Claude Bernard, who, like Beaumont, reached the pinnacle of medical fame despite having been a rather poor student of the field. Bernard decided not to wait for such a "lucky" accident as had fallen into Beaumont's hands. Instead, he took to creating stomach fistulas on purpose - but in animals, not humans.

In a series of brilliantly conceived and executed experiments in the mid-nineteenth century, Bernard showed that, contrary to the conventional wisdom of the time, the stomach was not the sole organ of digestion, nor was it even the principal one. The stomach, it turned out, was but an anteroom to the site of most of the real action: the small intestine, which he studied through fistulas also. By introducing foodstuffs directly into the duodenum, Bernard showed that the main processes of digestion occur throughout the length of the intestine, which not only finishes the protein demolition job started by the stomach, but also processes substances left relatively unscathed by the stomach, such as carbohydrates and fats. It does all this through the action of enzymes and bile salts from the liver, and of enzymes from the pancreas.

Now it is clear why one can live without a stomach. But since most of us are still very attached to ours, we need to treat it with care and respect so that we can look forward to a long and happy life together. One way to do that is to vanquish the stomach's chief nemesis, H. pylori, the cause of some of its worst ills. And a safe, effective approach to that task is with nature's gift to your stomach, mastic.


  1. The Merck Manual of Diagnosis and Therapy, 17th ed. Merck Research Laboratories, Whitehouse Station, NJ, 1999, pp. 245-56.
  2. National Institutes of Health Consensus Statement, "Helicobacter pylori in Peptic Ulcer Disease," Feb 1994, Vol 12, No. 1.

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