Anatomy and Embryology

DOROTHEA LIEBERMANN-MEFFERT ANDRÉ DURANCEAU HUBERT J. STEIN

ANATOMY OF THE ESOPHAGUS MACROSCOPIC FEATURES Configuration

The esophagus is the narrowest tube of the intestinal tract. It ends by widening into its most voluminous part, the stomach. At rest, the esophagus is collapsed; it forms a soft muscular tube that is flat in its upper and middle parts, with a presenting diameter of 2.5 x 1.6 cm. The lower esophagus is rounded, and its diameter is 2.5 x 2.4 cm.

Compression or constriction by adjacent organs, vessels, or muscles causes narrowing, which can be visualized by means of fluoroscopy and endoscopy. 1 ' 1 ' The aortic compression, which is left-sided and anterolateral, is caused by the crossing of the aortic arch, the left

Figure 1-1 Classic division of the esophagus and its topographic relationship to the cervical (C) and thoracic (Th) vertebrae. The approximate length of each segment is given, and the three narrowings of the esophagus are shown. More recently, the esophagus has been subdivided according to its different functions by Diamant (1989). Based on the embryology and main direction of lymphatic flow, Siewert (1990) proposed a subdivision of the thoracic esophagus at the level of the tracheal bifurcation for planning treatment strategies in patients with esophageal cancer. UES = upper esophageal sphincter, LES = lower esophageal sphincter.

Esophageal Length

Figure 1-2 Topographic anatomy of the esophagus shown from the cervical level (1) to the esophagogastric junction (6). Transverse section through the mediastinum shows the esophagus and its surrounding structures in the CT aspect. The close positional relationship among the esophagus, trachea, and vertebrae and the fascial planes is displayed. The thick dark lines are the prevertebral and previsceral fascia (arrows); the net-like pattern represents the respective areolar connective tissue. (Modified after Wegener, O.H.: Neuromuscular organization of esophageal and pharyngeal motility. Arch. Intern. Med., 136:524, 1976, with permission.)

Figure 1-3 Attachments of the esophagus. The upper end of the esophagus obtains a firm anchorage by the insertion of its longitudinal muscle into the cartilaginous structures of the hypopharynx (1) via the cricoesophageal tendon (2). The circular muscle is stabilized by its continuity with the inferior laryngeal constrictor muscles (1), which insert via the raphe to the sphenoid bone. Tiny membranes connect the esophagus with the trachea, bronchi, pleura, and prevertebral fascia (3 and 4). The attachment at the lower end by the phrenoesophageal membrane (5) is rather mobile, whereas the posterior gastric ligaments, such as the gastrosplenic, phrenicolienal, and phrenicogastric ligaments (6) and the lesser omentum (6), yield a tight adherence. UES = upper esophageal sphincter, LES = lower esophageal sphincter.

Figure 1-4 The posterior walls of the pharynx (4) and the esophagus (7 and 8) have been cut open in the midline. This is shown in a specimen (A) and half-schematically (B). The structures of the hypopharynx are exposed by retracting the overlying incised tissue and removing the mucosa. In the center lies the cricoesophageal tendon (6), which attaches at the longitudinal muscle layer of the esophagus (8) to the cricoid cartilage (2). The terminal branches of the left laryngeal recurrent nerve (9) are dissected and are seen lateral to the cricoesophageal tendon. Thyroid cartilage (1). (Specimen and photo courtesy of Liebermann-Meffert, Munich.)

Figure 1-5 A and B, Example of the tiny fiber membranes that connect esophagus (1), trachea (2), pleura (3), tracheal membrane (4), and cartilaginous structures (5). At their insertions, the fiber elements fan out to deep finger-shaped extensions between the muscular bundles of the esophagus (arrow) and into the membranous part of the trachea (double arrows). This texture, in conjunction with the elasticity of the membranes, certainly provides adequate adjustment during the movements of the esophagus. In case of rapid pull, the fibers eventually tear off the tissues in which they are anchored. (Human esophagus, transverse section, hematoxylin and eosin.) (Courtesy of Huber, Haeberle, and Liebermann-Meffert, Munich.)

Figure 1-6 Diaphragm and esophageal hiatus viewed from the abdominal aspect.

Figure 1-7 The phrenoesophageal membrane (PEM). The lower component of the membrane inserts on the gastric fundus. On the left, the diaphragm is held with a forceps. Diaphragmatic decussating fibers (long arrow) and a submembranous inlay of adipose tissue (short arrow) are seen. The PEM wraps the esophagogastric junction with a wide membranous collar. (Specimen and photo: Liebermann-Meffert, Munich.)

Figure 1-8 Diagram of the tissue organization and the supporting structures at the esophagogastric junction. The esophagus is opened alongside the greater and lesser curvatures. The luminal aspect is displayed from the left side. The fiber elements that attach the phrenoesophageal membrane to the muscle wall of the terminal esophagus are shown. The fibers are similar to those shown in Figure 1-5 . (Courtesy of Dr. Owen Korn, Munich and Santiago di Chile.)

Figure 1-9 Transverse section through the neck and upper chest of a human autopsy specimen viewed from a cranial aspect. 1 = esophagus, 2 = trachea, 3 = pleura, 6 = thyroid gland and vessels (arrow), and 8 = vessels. The histologic section shows the esophagus still in midline posterior position (A), whereas in the more distal level of the macroscopic cut surface (B), the esophagus has shifted toward the left. Note the intimate local relationship between the esophagus and the trachea. (From Liebermann-Meffert, D: In Fuchs, K..H., Stein, H.J., Thiede, A. [eds.]: Gastrointestinale Funktionsstörungen. Berlin, Springer, 1997, with permission.)

Figure 1-10 The position and relationships of the azygos vein, the thoracic duct, and the vagus nerve are shown from a right lateral aspect.

Figure 1-10 The position and relationships of the azygos vein, the thoracic duct, and the vagus nerve are shown from a right lateral aspect.

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