Final answer:
The smooth muscles of the esophagus develop from the mesoderm and are crucial for the process of peristalsis, which moves food from the mouth to the stomach.
Step-by-step explanation:
The smooth muscles of the esophagus develop from the mesoderm, which is one of the three primary germ layers formed during embryogenesis. In the esophagus, the muscularis layer changes according to its location: In the upper third of the esophagus, the muscularis is comprised of skeletal muscle, while in the middle third, it is composed of both skeletal and smooth muscle. In the lower third of the esophagus, it is entirely made up of smooth muscle, which is essential for the process of peristalsis - the series of wave-like movements that propel the bolus of food from the mouth to the stomach.