Human Anatomy - M.M. Kurepina, A.P. Ozhigova, A.A. Nikitina 2010

Internal Organs
Digestive System
Esophagus

The Esophagus is a muscular tube about 25 cm long (Atlas Fig. 175). It is divided into three parts: cervical, thoracic, and abdominal (Fig. 4.9). The cervical part begins without any sharp boundary from the Pharynx at the level of the VI cervical vertebra, passes behind the Larynx and Trachea, and, together with the latter, enters the thoracic cavity through the superior thoracic aperture. The thoracic part of the esophagus is located in the Mediastinum along THE Vertebral Column, initially behind the aortic arch (down to the IV thoracic vertebra), then to the right of the descending aorta. In the lower mediastinum, the esophagus is covered anteriorly by the Pleura and Pericardium. The posterior part of the esophagus lies adjacent to the vertebral column. Further down, the esophagus descends in front of the aorta, passes through the Diaphragm via a specific opening, and opens into The Stomach at the level of the XI thoracic vertebra. A sphincter is located at the junction of the esophagus and the stomach. The abdominal part of the esophagus is covered by the Peritoneum anteriorly and laterally.

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Fig. 4.9. Structure and Topography of the esophagus:

1 — superior esophageal constriction; 2 — middle (or aortic) esophageal constriction; 3 — inferior esophageal constriction; 4 — diaphragm; 5 — stomach; 6 — abdominal part; 7 — thoracic part; 8 — cervical part; 9 — pharynx

The esophagus has three clearly visible constrictions: at its origin from the pharynx, at the level where it crosses the aorta, and where it passes through the diaphragm. These constrictions develop only after birth. In young children, accidentally swallowed foreign objects most commonly lodge at these sites, where they can be detected using specialized X-ray examinations.

In newborns, the Water/144.html">Origin of the esophagus is located higher than in adults—at the level of the III cervical vertebra. By Puberty, the esophagus descends to the level of the V–VI cervical vertebrae, and in the elderly, down to the I thoracic vertebra.

The wall of the esophagus consists of four layers (Atlas Fig. 176B). The mucosa is lined with non-keratinized stratified squamous epithelium. In old age, signs of keratinization may appear in the proximal part of the esophagus. The epithelium protects the esophagus during the passage of a coarse bolus of food. The submucosa is well-developed and contains small mucous glands. Solitary small lymphatic follicles and aggregates of lymphocytes are located around their secretory units. Esophageal cardiac glands lie within the lamina propria of the mucosa near the stomach. These are simple branched tubular glands whose secretory Cells produce mucus and chlorides. The secretory units also contain A large number of endocrine cells. The muscularis mucosae is well-developed. Its contraction forms deep longitudinal folds in the esophageal lumen, giving the organ's lumen a stellate appearance. During the passage of a coarse food bolus, the Muscle cells relax, and the diameter of the esophagus expands significantly (Fig. 4.10).

Fig. 4.10. Passage of food through the esophagus during swallowing:

1 — esophagus; 2 — contracted Muscles; 3 — food bolus; 4 — stomach

The submucosa of the esophagus is well-developed. It is formed by Connective Tissue containing vascular and nerve plexuses. The venous and lymphatic plexuses are particularly prominent. The secretory units of the esophageal glands proper, which produce a mucous secretion, are also located here. Most of these glands lie in the upper third of the esophagus. The mucus they secrete lubricates the epithelial surface and facilitates the passage of the food bolus.

The muscularis externa in the cervical part of the esophagus consists of striated muscle, which is a continuation of the pharyngeal muscles. In the lower two-thirds, it is replaced by smooth muscle. Thickening of the circular muscle layer forms sphincters: the upper esophageal sphincter at the level of the cricoid Cartilage of the larynx, and the lower esophageal sphincter at the junction with the stomach. Contraction of the muscular coat promotes the movement of food toward the stomach (Fig. 4.10).

The adventitia, composed of loose connective tissue, anchors the esophagus to the surrounding Organs, while the abdominal part of the esophagus is covered by the peritoneum, which, together with the underlying connective tissue, forms the serosa.

The Blood supply to the esophagus is provided by Branches of the inferior thyroid artery, esophageal and bronchial Branches of the Thoracic Aorta, and the left gastric artery. The esophagus is innervated by the Autonomic Nervous system. Sympathetic fibers from the esophageal plexus and parasympathetic fibers within the Vagus nerve form the myenteric and submucosal plexuses in the esophageal wall. These plexuses also include well-defined intramural ganglia.