What side is the stomach on? Is this a muscle? What is its structure? How does it work? Find out all the answers you need!

The stomach is a wonderful organ with unique characteristics and important functions for digestive health. We explain here how it works and how to take care of it.

What side is the stomach on?

The stomach is a compliant J-shaped organ located in the upper left quadrant of the abdomen. It can expand 50 times its size compared to when it is empty.

What side is the stomach on really? It changes in size, shape, and position depending on the person’s posture and whether or not they are full. In an adult, its average capacity is 1.5 liters.

Its main functions are to receive, store and soften the ingested food, turning it into a liquid mixture. It then releases it into the duodenum in appropriate amounts. In parallel, hydrochloric acid and the secreted enzymes that make up gastric juice have the important mission of neutralizing harmful bacteria and initiating protein digestion.

What happens in the stomach when eating?

Now that you know what side is the stomach on, you should know what it does. Fasting, a minimum gastric juice production is maintained. Before eating the food, hunger, the sight and smell of it will increase the production of gastric juice and prepare the stomach to receive the food. This is known as the cephalic phase of digestion and is responsible for approximately 30% of gastric juice production.

Once we start eating and the food reaches the stomach, the organ relaxes and becomes distended. The enzyme pepsin appears and gastric juice secretion is stimulated. This is the gastric phase of digestion, which lasts between 2 and 3 hours.

The stomach is mainly made up of involuntary smooth muscle. In conjunction with the secretion of substances, motility increases. These rhythmic movements favor chemical digestion, by facilitating the mixing between food and the substances produced. It results in mechanical digestion. Both processes turn food into chyme.

When the food passes into the duodenum, the secretion of gastric juice returns to its initial state. In this, the intestinal phase of digestion, the remaining 10% of gastric juice is produced.

The stomach is not a nutrient absorption area. There is minimal absorption of the initial products of protein digestion and none of the fats. However, there’s an absorption of simple sugars, water, and alcohol.

Other functions

The acidic stomach environment allows the ionization of ingested calcium, so that it is subsequently absorbed in the intestine. In this way, the stomach plays a key role in bone health.

Stomach secretion is necessary for the absorption of iron, magnesium, vitamin B12, and ascorbic acid. At the same time, the stomach participates in the control of appetite and obesity. It takes part through the production of substances that interact with the fibers of the vagus nerve.

On the other hand, the stomach is a complex organ in its immune part. It plays a crucial role in defense against microorganisms present in ingested food.


The stomach is divided into 3 main parts: fundus, body, and pyloric region. The fundus of the stomach is the largest, most distensible part that contains the parietal cells inside.

The stomach borders in the upper part with the abdominal portion of the esophagus, with which it communicates through the cardia. With the duodenum, with which it communicates through the pylorus, it borders in the lower part.

Due to its location, it is also related to other organs, such as the liver, pancreas, spleen, transverse colon, kidney, and the left adrenal gland.

Layers and cells

Its wall is divided into 4 layers, which are overlapping:

  • Mucosa: the innermost, covered by the epithelium. It produces about 2 liters of gastric juice a day.
  • Submucosa: it has a rich capillary circulation.
  • Muscular.
  • Serosa: the outermost, which is the part of the peritoneum that lines the stomach.

The gastric crypts are lined by the following types of cells:

  • Mucous: protects the stomach lining.
  • Parietal or oxyntic: they secrete hydrochloric acid that is responsible for chemical digestion and sterilization of food. In addition, they produce a protein for transporting vitamin B12.
  • Main cells: these secrete pepsinogen which is inactive, and converts into an active enzyme, pepsin, when exposed to hydrochloric acid. They also produce gastric lipase, which continues the digestion of fats initiated by lingual lipase.
  • Endocrine cells: synthesize hormones, such as gastrin and histamine, which increase the secretion of gastric juice. Somatostatin and ghrelin too.

Why doesn’t it digest itself?

The acidic pH and pepsin could damage the gastric mucosa. However, it is capable of withstanding numerous attacks of various origins.

Multiple factors intervene to avoid or cushion this risk. The main one is a mucus and bicarbonate gel that acts as a barrier, separating the gastric mucosa from the stomach contents.

Another factor involved is the remarkable ability to repair the epithelium when injured. As well as the production of substances called prostaglandins, capable of improving acid resistance, activating the secretion of mucus and bicarbonate.

An additional protective line is the rich vascular bed of the submucosa, through which the bicarbonate that mucosal cells need to neutralize gastric acidity circulates. At the same time, oxygen and micronutrients contribute to cell repair.

What happens if this protection fails?

The gastric wall faces the impact of numerous circumstances capable of causing damage and inflammation of its mucosa (gastritis). Some of these lesions due to microbes, the most prominent being Helicobacter pylori infection.

Other injuries are autoimmune or allergic in nature. In turn, there are harmful chemical agents, such as non-steroidal anti-inflammatory drugs or NSAIDs, among which is aspirin.

Sustained mucosal erosion can lead to atrophy or loss of parietal cells and secondary anemia. If this process continues, gastric cancer can occur.

Another consequence of the persistent imbalance between the acidity of the stomach contents and the protective mechanisms is the development of gastric mucosa tears. These are ulcers.

The acid secretion of the stomach also intervenes in the presentation of diseases beyond this organ. This is how gastroesophageal reflux can lead to erosive esophagitis and even esophageal cancer.

Tips for caring for digestive health

The health of the stomach is of great importance. Here we tell you what actions you can take to take care of this organ.

Give up smoking

Smoking is, in fact, a major risk factor for gastric and duodenal ulcers. Also for stomach cancer.

Responsible use of medicines

Self-medicating is a very risky practice. All drugs have potential adverse effects.

Commonly used over-the-counter medications, such as aspirin, naproxen, and piroxicam, can be very damaging to the stomach. For this reason, you should not use them excessively and without consulting a doctor.

You should use medications that inhibit or hinder acid production, such as omeprazole or ranitidine under medical supervision. Since the maintenance of the acidic environment within the stomach has crucial functions for health.

Other measures

Other measures recommended by the Spanish Foundation for the Digestive System to prevent cancer are avoiding obesity, exercising daily, consuming plenty of fruits and vegetables, and moderate alcohol consumption.

Take care of your stomach

Therefore, taking care of the stomach is not just avoiding heavy or slow-digesting meals. All healthy lifestyle-enhancing habits help reduce the risk of gastritis, gastroesophageal reflux, and cancer.

Consult a gastroenterologist if you have relevant symptoms in your abdomen or in any part of the digestive system. Do not let the time pass by.

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