The esophagus is an important part of the human organ, which relies on muscle contraction and relaxation to deliver food to the stomach. The wall of the esophagus is divided into 4 layers, which are the mucosa, submucosa, muscularis propria, and tunica albuginea. 1. Mucosal layer: The epithelium of the mucosal layer is thicker and serves to resist friction and protect the esophagus. 2. Submucosa: The submucosa is composed of loose connective tissue and contains glands that secrete mucus into the lumen of the esophagus. Multiple longitudinal folds are formed between the mucosa and submucosa, which disappear as food passes through the esophagus. 3. Muscularis propria: The muscularis propria of the esophagus is divided into two layers, inner and outer, about 2 mm thick, with elastic fibers between the two layers. 4. Epithelium: It is composed of loose fibrous tissue and contains blood vessels and lymphatic vessels.