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How does food become chyme in the stomach?

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Diagram of the human digestive system viewed from the front, showing and labeling organs including the mouth, teeth, tongue, salivary glands, pharynx, esophagus, liver, stomach, gallbladder, pancreas, large intestine, small intestine, appendix, rectum, and anus. — digestion The human digestive system as seen from the front.

In the stomach, food is converted into chyme—a thick, semifluid mass—through a combination of mechanical and chemical processes.12

Mechanical Digestion

Upon the entry of food, the stomach muscles undergo rhythmic contractions that churn and knead the contents. These peristaltic waves move the mixture toward the pylorus, physically breaking down food particles to make them smaller and more soluble.23

Chemical Digestion

Simultaneously, the gastric glands in the stomach lining secrete gastric juice, which is a mixture of water, electrolytes, mucus, and enzymes. Key components include:14
* Hydrochloric acid: This creates a highly acidic environment necessary to activate enzymes and initiate the breakdown of food.154
* Pepsin: An enzyme that begins the digestion of proteins.15

As these substances mix with the food through muscular activity, the contents are transformed into chyme. Once the food particles are sufficiently reduced in size and composition, the stomach discharges the chyme into the small intestine for further digestion and nutrient absorption.123