Final answer:
When CCK contracts the pyloric sphincter, it regulates the movement of chyme from the stomach to the small intestine.
Step-by-step explanation:
When the hormone cholecystokinin (CCK) contracts the pyloric sphincter, it helps regulate the movement of chyme from the stomach into the small intestine. The pyloric sphincter acts as a filter, allowing liquids and small food particles to pass through into the duodenum while keeping larger particles in the stomach for further digestion. By contracting the pyloric sphincter, CCK helps control the release of chyme in a controlled manner, preventing overwhelming the small intestine's capacity.