28: Overview: Anatomy and Pathophysiology of Benign Esophageal Disease

Introduction

The term “esophagus” derives from the Greek root “oisein” (to carry) and “phagos” (to eat). The esophagus' intricate components perform in symphony to provide a muscular conduit between the pharynx and stomach. Even small deviations in structure can lead to dysfunction. Benign esophageal lesions can obstruct the esophageal lumen and produce symptoms. This chapter discusses esophageal development and anatomy as well as the pathophysiology of benign esophageal diseases. 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.

Embryology

The esophagus and trachea both form from a medial ventral diverticulum arising from the primordial foregut at approximately day 22 or 23 of fetal development (Fig. 28-1). The foregut divides into trachea and esophagus during week 4. The stomach bud forms posteriorly shortly thereafter. Both the trachea and esophagus elongate between days 23 and 34 or 36. It is thought that esophageal lengthening occurs by ascent of the pharynx rather than descent of the stomach. By approximately day 36, the trachea and esophagus have completely separated.¹

The esophageal wall is derived from both endoderm and mesoderm. The endoderm forms the epithelium and glands, whereas the mesoderm eventually forms the muscular layers, connective tissue, and angioblasts. During the seventh and eighth weeks of development, the esophageal epithelium proliferates to fill the lumen, leaving only small irregular channels open. These channels grow to form vacuoles, which then coalesce to create one lumen by the 10th week of gestation (Fig. 28-2). Ciliated epithelium initially lines the embryological esophagus, but it is replaced by the fourth month of gestation by stratified squamous epithelium. By the sixth week, the mesenchymal circular muscular coat forms, and the splanchnic mesenchyme surrounds the esophagus and trachea. The splanchnic mesenchyme enables the formation of the smooth muscle of the lower esophagus. The longitudinal musculature forms during weeks 9 through 12, and the muscularis mucosa forms by week 16. Blood vessels start to enter the esophageal wall in week 28, but the lymphatic capillaries do not form until the third to fourth month of gestation.¹

Congenital anomalies of the esophagus occur in 1 in 3500 births and typically are the result of a genetic defect or maternal event. They are more common in premature infants, and 60% are associated with other congenital anomalies, including ...