The esophagus is a muscular tube which serves as a conduit between the pharynx and stomach. Derived from the Greek roots oisein (to carry) and phagos (to eat), the esophagus conducts an arpeggio of muscular contractions as it winds through the neck, chest, and abdomen. With its location centrally in the chest and proximity to vascular structures, the heart, the spine, and the airway, it was rendered “out of reach” to early surgeons. However, with modern techniques and the advent of minimally invasive and endoscopic approaches, esophageal intervention is easily accessible to a range of specialists. This chapter reviews the embryologic development and anatomy of the esophagus, as well as benign lesions that are encountered in clinical care. Chapter 29 details the surgical and endoscopic approaches to these diseases. Motility disorders and congenital esophageal diseases are discussed in more detail in Chapters 33 and 51, respectively.
Human development is divided into two distinct phases: the embryologic period, encompassing the time from fertilization until the ninth week of gestation, and the fetal period, lasting from the conclusion of the ninth gestational week until birth. The primitive esophagus forms early in the embryologic period and undergoes changes well into the fetal period, with full function not developing until after birth.1
During the fourth week of development, the primitive digestive tract divides into the foregut, midgut, and hindgut. A ventral bud, the tracheobronchial diverticulum, arises from the foregut during the fourth week and elongates to become the respiratory tract. A tracheoesophageal septum develops early in this process, separating the ventral laryngotracheal tube and the dorsal esophagus (Fig. 28-1). Both the primitive esophagus and trachea elongate from day 22 to 36. By day 36, the trachea and esophagus have separated completely.2
The embryonic tracheoesophageal septum forms to separate the esophagus and trachea. The lungs then bud off ventrally from the trachea.
The esophageal wall is derived from endoderm, forming the epithelium and glands, and mesoderm, forming the muscular layers, connective tissue, and angioblasts. During the seventh and eighth weeks of development, esophageal epithelium proliferates to fill the lumen, leaving only small irregular channels. These channels grow to form vacuoles, which coalesce by week 10 to form a single lumen lined with ciliated epithelium (Fig. 28-2). Stratified squamous epithelium subsequently replaces the ciliated epithelial cells.
A. Epithelial cells initially fill the obliterated esophagus, then isolated vacuoles form (B) and eventually coalesce (C) to form a patent lumen (D).
The striated muscle of the upper esophagus is derived from the mesenchyme of branchial arches 4, 5, and 6, whereas the lower esophagus ...