Final answer:
The myenteric plexus, located between the two layers of the muscularis externa, is responsible for controlling the motility of the gastrointestinal tract.
Step-by-step explanation:
The nerve plexus located between the two layers of the muscularis externa is the myenteric plexus (plexus of Auerbach), and its function is to control the gastrointestinal motility, particularly the rhythm and force of the contractions of the muscularis. The enteric nervous system contains the myenteric plexus and provides intrinsic innervation of much of the alimentary canal, from the esophagus to the anus. This system features approximately 100 million motor, sensory, and interneurons, unique to this part of the peripheral nervous system, and is crucial for the coordinated muscular movements required for food to travel through the digestive tract, a process known as peristalsis.