Why do the oesophagus and intestines have muscle layer?

??Why do the oesophagus and intestines have muscle layer?
The contraction of these muscle layers propels food forward or backward (if you're vomiting) through the digestive tract. The process by which this happens is called peristalsis.Why do the oesophagus and intestines have muscle layer?
to move food through the intestines. This is called peristalsis.