The stomach performs both mechanical and chemical digestion.
Mechanical Digestion in the Stomach
Mechanical digestion in the stomach involves the physical breakdown of food. This is achieved primarily through powerful muscle contractions. These contractions, called peristaltic contractions, move the food (now a bolus) from the fundus (the upper part of the stomach) towards the pylorus (the lower part, leading to the small intestine). This churning action mixes the food with gastric juices, further breaking it down into smaller particles.
Chemical Digestion in the Stomach
Chemical digestion in the stomach involves the breakdown of food molecules through enzymatic action. Gastric glands in the stomach lining secrete gastric juice, which contains hydrochloric acid (HCl) and pepsinogen. HCl creates an acidic environment, activating pepsinogen into pepsin, an enzyme that begins the breakdown of proteins. This process is crucial for protein digestion and preparing the food for further processing in the intestines.
In Summary: The stomach plays a vital role in both the physical (mechanical) and chemical breakdown of food, preparing it for absorption in the intestines. The reference material explicitly states that "mechanical and chemical digestion" takes place in the stomach.
