What's in Your Stomach's Gastric Juice?

Acids, Enzymes, Mucus, and More

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As soon as you put food into your mouth your stomach begins releasing gastric juices. This liquid mixture will help dissolve food once it reaches the stomach and the process of digestion begins.

What are these juices made of and how do they keep your body healthy? Let's take a tour of the first stage of your digestive system and find out.

How Your Body Produces Gastric Juices

The food you chew and swallow is called a bolus.

It mixes with the gastric juices secreted by special glands found in the lining of your stomach. They include the cardiac glands at the top part of the stomach, the oxyntic glands in the main body of the stomach, and the pyloric glands in the antrum or the lowest part of the stomach.

Each of the glands contains cells that make specific components that together are called the gastric juices. Neck cells secrete bicarbonate and mucous, parietal cells secrete hydrochloric acid, chief cells secrete pepsinogen, and enteroendocrine cells secrete various hormones. However, not all stomach glands contain every type of cell.

Breaking Down the Gastric Juices

Gastric juice is made up of water, electrolytes, hydrochloric acid, enzymes, mucus, and intrinsic factor.

Hydrochloric acid is a strong acid secreted by the parietal cells, and it lowers your stomach's pH to around 2. Hydrochloric acid converts pepsinogen into pepsin and breaks various nutrients apart from the food you eat.

It also kills bacteria that comes along with your food.

Pepsinogen is secreted by chief cells, and when it's in the presence of hydrochloric acid, it's converted to pepsin. Pepsin breaks apart tertiary and secondary protein structures to make it easier for the digestive enzymes in the small intestines to work later.

Gastric lipase is another digestive enzyme made by the chief cells. It helps break down short and medium chain fats.

Amylase is also found in gastric juices, but it isn't made by the stomach. This enzyme comes from saliva and travels along with the bolus into the stomach. Amylase breaks down carbohydrates, but it doesn't have much time to work on the stomach because the acidity stops it. But that's okay, your small intestine makes more amylase later on.

Intrinsic factor is secreted by parietal cells and is necessary for your body to absorb vitamin B-12. This is essential for healthy nervous system function and blood cell production.

Finally, the gastric juices contain water and mucus. The mucus is secreted by the neck cells and helps coat and protect your stomach lining from the acid environment.

It All Works Together

Your stomach muscles squeeze and churn to mix the bolus with all of these digestive juices. The liquid mixture is called chyme. When it's ready, your stomach squirts the chyme into the small intestine where digestion continues and absorption of those all-important nutrients occurs. 

Sources:

Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. 6th ed. Belmont, CA: Wadsworth Publishing Company; 2013.

Smolin LA, Grosvenor, MB. Nutrition: Science and Applications. 4th ed. Hoboken, NJ: ​Wiley Publishing Company; 2016.

Wallace M. Your Digestive System and How It Works. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). 2013.

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