Final answer:
Gastrin main role is to stimulate the secretion of gastric acid and gastric motility, aiding in breaking down food in the stomach during the gastric phase of digestion, which starts when food reaches the stomach.
Step-by-step explanation:
The role of gastrin in food digestion and absorption is to stimulate gastric acid secretion and motility. Gastrin is the main digestive hormone of the stomach and is secreted in response to the presence of food. It activates the secretion of gastric acid by the parietal cells of the stomach mucosa. This increase in gastric acid helps to break down food, preparing it for further digestion and absorption in the small intestine. Additionally, the gastric phase of digestion, which begins when food reaches the stomach, involves the secretion of gastrin and subsequent production of gastric acids and enzymes for processing ingested materials.