Anatomy · MU Sofia

Histology · Oesophagus

Covers the histology of the oesophagus, moving from the lumen outward through the four wall layers. It describes the nonkeratinised stratified squamous epithelium with its basal, intermediate and superficial cell layers, then the lamina propria and muscularis mucosae. It also notes the submucosal glands, the change from striated to smooth muscle along the muscularis propria, and the adventitia. Brief remarks on staging and protective roles are included.

Inside: 1 section · 2 labelled pictures · 15 flashcards · 3 min

Topic 260 of 264 in the MU Sofia syllabus for Anatomy (Dental Medicine, Year 2). The free AceMed note covers it in 1 section, about 442 words (3 min of reading), with 15 flashcards.

In this note

  1. Introduction

Introduction

Definition / general

  • Esophagus is a muscular tube that extends from the pharynx to the gastroesophageal junction; it has typical gastrointestinal (GI) tract layering (mucosa, submucosa, muscularis propria / externa, adventitia) around a central lumen as well as 2 muscular sphincters (upper and lower).

Microscopic (histologic) description

  • Esophagus is arranged in 4 concentric layers following a typical GI layering scheme; listed from the lumen outward, these layers are mucosa, submucosa, muscularis propria / externa, adventitia
  • Esophageal mucosa
  • Epithelium: nonkeratinized stratified squamous epithelium
  • Innermost layer of the esophageal mucosa, lining the lumen
  • Other cells present: melanocytes, endocrine cells, Langerhans cells, Merkel cells, T cells
  • Basement membrane separates the epithelium from the underlying lamina propria
  • Basal layer: < 15% of the mucosal thickness, usually 2 - 3 cells thick, comprised of basophilic proliferative cells with minimal cytoplasm, mitotic figures are found only here (under normal conditions) (Richter: The Esophagus, 5th Edition, 2012)
  • Intermediate layer: these glycogen rich squamous cells have more cytoplasm than those of the basal layer (i.e., decreased N:C ratio)
  • Superficial layer: cells appear more flattened as they mature and approach the lumen, many cells are anucleate
  • Lamina propria: composed of loose fibrovascular connective tissue
  • Situated between the epithelium and muscularis mucosae
  • Folds form papillae; these usually extend ~one - third to half of epithelial thickness (Richter: The Esophagus, 5th Edition, 2012)
  • Scattered inflammatory cells may be present
  • Muscularis mucosae: composed of smooth muscle
  • Begins proximally at the cricoid cartilage and becomes thickened distally
  • In the lower esophagus, it may play a protective role against stomach acid erosion (Ann N Y Acad Sci 2013;1300:261)
  • May resemble muscularis propria / externa which is important for accurate American Joint Committee on Cancer (AJCC) staging of adenocarcinoma in this region (J Thorac Dis 2014;6:S289)
  • Submucosa: connective tissue
  • Contains fibroblasts / collagen, nerves, sparse ganglia (Meissner plexus), lymphatic channels, blood vessels and submucosal (seromucous) glands
  • Submucosal glands are comprised of mucinous cells surrounding a central lumen that produce acid mucin and empty into the esophagus via squamous lined ducts
  • Submucosal glands are a significant identifying landmark of esophagus on biopsy or resection specimen (Richter: The Esophagus, 5th Edition, 2012)
  • Muscularis propria (i.e., muscularis externa)
  • Composed of striated skeletal muscle in the proximal third of the esophagus, smooth muscle in the distal third and a mixture of both skeletal and smooth muscle in the middle third

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