Final answer:
The esophagus is a muscular tube that connects the pharynx to the stomach, averages 25 cm in length in adults, and features peristalsis for moving food and a lower esophageal sphincter to prevent reflux.
Step-by-step explanation:
Definition of the Esophagus
The esophagus is a long, narrow, muscular tube that serves as a passageway for food traveling from the pharynx to the stomach. In adults, the esophagus typically measures around 25 cm (10 in.) in length. Posterior to the trachea and encased within the mediastinum of the thorax, it descends straight down through the thorax, passes behind the heart and lungs, and proceeds to the stomach, traversing the esophageal hiatus, an opening in the diaphragm. The inner lining of the esophagus features a mucus-secreting membrane aiding in the smooth passage of food. Food movement through the esophagus is facilitated by peristalsis, a series of wave-like contractions. At the stomach entrance, a muscular valve called the lower esophageal sphincter regulates the flow of food into the stomach and prevents its reflux back into the esophagus.