Esophagus

The esophagus is a hollow tubular organ that serves to conduct food masses from the pharynx to the stomach. The length of the esophagus in an adult is 25-27 cm. The esophagus is somewhat flattened in the anteroposterior direction in its upper part, and in the lower section (below the level of the jugular notch of the sternum) it resembles a flattened cylinder. The esophagus begins at the level of the pharyngeal-esophageal junction at the level of the V-VII cervical vertebrae and flows into the stomach at the level of the IX-XII thoracic vertebrae. The lower border of the esophagus in women is usually located 1-2 vertebrae higher than in men.

The cervical part of the esophagus (pars cervicalis) is 5-7 cm long. It is surrounded by loose connective tissue, which passes below into the cellular tissue of the posterior mediastinum. In front, the cervical part of the esophagus is adjacent to the membranous wall of the trachea, with which the esophagus is closely connected by loose fibrous connective tissue. The left recurrent laryngeal nerve usually runs from bottom to top along the anterior surface of the cervical part of the esophagus. The right recurrent laryngeal nerve usually runs along the right lateral surface of the esophagus, behind the trachea. Behind, the esophagus is adjacent to the spine and the long muscles of the neck, covered by the prevertebral plate of the cervical fascia. On each side of the cervical part of the esophagus is a vascular-nerve bundle (common carotid artery, internal jugular vein, vagus nerve).

Thoracic esophagus

(pars thoracica) is 16-18 cm long. In front of the esophagus in the chest cavity are successively located the membranous wall of the trachea, below - the aortic arch, the beginning of the left main bronchus. Between the back wall of the trachea, the left main bronchus on one side and the esophagus on the other are muscle and connective tissue bundles of unstable bronchoesophageal muscles and ligaments. Below, the esophagus passes behind the pericardium, that part of it that corresponds to the level of the left atrium.

Behind the thoracic part of the esophagus is the spine (up to the level of the III-IV thoracic vertebrae). Below, behind the esophagus and slightly to the right of it, is the thoracic lymphatic duct, and even lower is the hemiazygos vein.

The relationship between the esophagus and the aorta is complex. The aorta initially contacts the left surface of the esophagus, passes between it and the spine, and in the lower sections the thoracic part of the esophagus is located in front of the aorta.

The vagus nerves are adjacent to the thoracic part of the esophagus from the sides below. The left nerve runs along the left side closer to the anterior surface, and the right nerve runs closer to the posterior surface of the esophagus. At the level of the II-III thoracic vertebra, the right surface of the esophagus is often covered by the right mediastinal pleura.

The so-called pleuroesophageal muscle runs from the right surface of the lower third of the thoracic part of the esophagus to the right mediastinal pleura.

The abdominal part of the esophagus (pars abdominalis), which is 1.5-4.0 cm long, goes obliquely downwards and to the left from the esophageal opening of the diaphragm to the area of transition into the stomach. The esophagus in the abdominal cavity is in contact with the left leg of the lumbar part of the diaphragm, and in front - with the caudate lobe of the liver. The left vagus nerve is located on the anterior wall of the esophagus, the right - on the posterior wall. In 80% of cases, the esophagus in the abdominal cavity is covered with peritoneum on all sides, in 20% of cases its posterior wall is devoid of peritoneal cover.

The esophagus does not have a strictly straight course, it forms small bends. The esophagus is located along the midline to the level of the VI cervical vertebra, then makes a slight bend to the left in the frontal plane. At the level of the II-III thoracic vertebra, the esophagus shifts to the right to the midline. The anteroposterior bend of the esophagus is located between the level of the VI cervical and II thoracic vertebrae (corresponds to the bend of the spine). Below the level of the II thoracic vertebra, the esophagus again forms a bulge in front (due to the proximity to the aorta). When passing through the diaphragm, the esophagus deviates forward.

The esophagus has narrowings that are located in the area of the pharyngeal-esophageal junction, behind the aorta (level IV thoracic vertebra) and in the area of the esophageal opening of the diaphragm. Sometimes there is a narrowing behind the left main bronchus.

The wall of the esophagus consists of four layers: the mucous membrane, the submucosa, the muscular and adventitial membranes (Fig. 225). The wall thickness is 3.5-5.6 mm.

The mucous membrane (tunica mucosa) of the esophagus wall is lined with multilayered flat nonkeratinizing epithelium (25-35 layers of epithelial cells). At the level of the upper third of the esophagus, the thickness of the epithelium is somewhat less than in other parts of the organ. The basal membrane (0.9-1.1 μm thick) is fenestrated. The proper plate of the mucous membrane is well defined, forming numerous papillae that protrude deep into the integumentary epithelium. In the upper and especially in the lower parts of the esophagus are located the cardiac glands, similar to the glands of the stomach with the same name (they contain mucous and a small amount of parietal and endocrine cells). The thickness of the proper plate in the areas where the cardiac glands are located increases significantly. The muscular plate of the mucous membrane thickens in the direction from the pharynx to the stomach.

The submucosa of the esophagus (tela submucosa) is well developed; it contributes to the formation of 4-7 distinct longitudinal folds of the mucous membrane. In the thickness of the submucosa, along with vessels, nerves, cells of various natures (lymphoid, etc.), there are 300-500 multicellular complex alveolar-tubular glands of the mucous type. These glands contain individual endocrine cells.

The muscular membrane of the esophagus (tunica muscularis) is represented in the upper third by striated muscle fibers. In the middle part of the esophagus, they are gradually replaced by smooth myocytes. In the lower part of the esophagus, the muscular membrane consists entirely of bundles of smooth myocytes. Muscle fibers and myocytes are located in two layers: the inner layer is annular, the outer layer is longitudinal. In the cervical part of the esophagus, the annular layer is 2 times thicker than the longitudinal one. In the thoracic part, both layers are equal in thickness, in the abdominal part, the longitudinal layer predominates in thickness. The muscular membrane determines both the peristalsis of the esophagus and the constant tone of its walls.

The adventitia covers the esophagus from the outside. The adventitia is most clearly expressed above the diaphragm. At the level of the diaphragm, the adventitia is significantly thickened with fibrous fibers associated with the fascial fibers of the diaphragm. The abdominal part of the esophagus is completely or partially covered by the peritoneum.

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