Final answer:
The ileocecal valve is a sphincter that separates the small intestine's ileum from the large intestine's cecum, and prevents backflow into the ileum.
Step-by-step explanation:
The ileocecal valve is a sphincter muscle that separates the small intestine and the large intestine. Specifically, it marks the junction between the ileum, the last part of the small intestine, and the cecum, the first portion of the large intestine. The ileocecal valve's main function is to regulate the flow of chyme from the small intestine to the large intestine, and to prevent backflow into the ileum.