Final answer:
The pyloric sphincter is made up of smooth muscle and is responsible for regulating the passage of food from the stomach to the small intestine.
Step-by-step explanation:
The pyloric sphincter is located at the lower end of the stomach, leading into the duodenum of the small intestine. It is made up of smooth muscle, which is responsible for controlling the passage of partially digested food from the stomach to the small intestine. Sphincters are anatomical structures composed of muscle fibers that can restrict flow when contracted. In the gastrointestinal tract, different sphincters serve varying functions. Unlike skeletal muscles, which are under voluntary control, smooth muscles are involuntary and facilitate movements and flows within the body without our conscious involvement. The pyloric sphincter's smooth muscle allows it to perform its function automatically, regulating the movement of chyme (the semi-fluid mass of partially digested food) into the small intestine for further digestion and absorption.