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How does the Stomach Function?

What exactly happens in our stomachs when we eat? Even before we have taken

the first bite of a meal, the brain sends impulses to the stomach. These impulses

start the production of secretions in the stomach and the upper part of the

stomach, which acts as a reservoir, expands. The food passes into the stomach

through the cardia at the stomach entrance. This is a muscle that acts like

a valve, closing the top of the stomach. The top part of the stomach, the fundus,

is where food and the air that we swallow with every bite is collected. This is

where the stomach volume starts to adapt. The fundus is an extremely adaptable

structure. The more food goes into the stomach, the more it actively expands.

In the middle part of the stomach, called the body, gastric juice is produced and

mixed with the mass of chewed food. The main component of gastric juice is

gastric acid. This eliminates bacteria in the food and also helps to prepare the

food for the following stages of digestion. The muscular contractions of

the stomach wall churn the food mass and mix it with gastric juice. Three

contractions per minute move the food mass back and forth. After a certain time,

the contents of the stomach are adequately broken down and mixed and are

passed in small quantities into the intestine via the pylorus. As the stomach

empties, it gradually returns to its previous size.

Bayer - Science For A Better Life