The Esophagus is a muscular tube, about 25 cm long that lies posterior to the trachea. The esophagus begins at the inferior end of the laryngopharynx, passes through the neck, and enters the mediastinum anterior to the vertebral column.
- It pierces the diaphragm through an opening called the esophageal hiatus and ends in the superior portion of the stomach.
- It consists of the following layers-
a) The mucosa of the esophagus consists of non keratinized stratified squamous epithelium, lamina propria, and a muscularis mucosae and contains mucous glands. The stratified squamous epithelium protects against abrasion and wear and tear from food particles that are chewed, mixed with secretions, and swallowed.
b) The submucosa contains areolar connective tissue, blood vessels, and mucous glands.
c) The muscularis of the esophagus is made up of skeletal muscle and smooth muscle. At each end of the esophagus, the muscularis forms two sphincters the upper esophageal sphincter, which consists of skeletal muscle, and the lower esophageal (cardiac) sphincter, which consists of smooth muscle. The upper esophageal sphincter regulates the movement of food from the pharynx into the esophagus, the lower esophageal sphincter regulates the movement of food from the esophagus into the stomach.
d) The superficial layer of the esophagus is known as the adventitia because the areolar connective tissue of this layer is not covered by mesothelium. The adventitia attaches the esophagus to surrounding structures.