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Inglés, Reading

8° Básico

The stomach

Its shape is similar to a J-shaped pouch. It is located beneath the ribs, in the upper portion of the abdominal cavity, to the bottom left of the liver.

Is a hollow organ with a capacity to increase its size up to 20 times. It receives the food that has been semi-grinded-up and mixed in the mouth.

It is made up of:

– Fundus: a zone where gases are accumulated.
– Body: the largest portion
– Pyloric Antrum: narrowing area

In addition, it has the following structures:

– Cardia: located at the upper part of the stomach, it is a muscular layer with a sphincter shape. It is connected with the esophagus.
– Pylorus: joins the stomach with the small intestine.

There are two sphincters at the upper and lower part of this organ. The first is the lower esophageal sphincter which connects the stomach with the esophagus. It’s like a door opening and closing, allowing the passage of food towards the stomach and blocking its return, a problem known as regurgitation. The final part of the stomach connects with the duodenum (first part of the small intestine) through the pyloric sphincter (similar to the esophageal sphincter).

The muscle layers that make up the walls of the stomach play an essential role, as they contract and relax, easing the digestive process. Food is blended with stomach fluids called gastric juices, which are very corrosive and break down the food bolus.

 Even though not yet absorbed, food goes through great alterations in the stomach. Its anatomical shape allows the mixing of substances, preparing them for the next step: the small and large intestines.

The work of the stomach

After the food bolus moves from the esophagus to the stomach, the vagus nerve stimulates the secretion of gastric juices within the stomach. When they are combined with food, a semi-liquid substance is formed called chyme, which stimulates the stomach walls, facilitating peristalsis (muscular contractions that enable food to advance). Once this process ends, chyme is ready to continue its journey and move on towards the small intestine.

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