Esophagus -- conducts food from oral cavity to stomach. Start by reviewing the general plan of the gastrointestinal tract (Fig. 15-2), noting especially the four major layers which are clearly seen in the esophagus:

• Mucosa
  • The epithelial lining of various types
  • Lamina propria of connective tissue
  • Thin muscularis mucosae of smooth muscle
• Submucosa containing blood vessels, lymphatics, and nerves
• Muscularis: two thick layers of smooth muscle for peristalsis
• Adventitia or serosa: outer connective tissue covering

Examine the preserved-mounted specimens of the various regions of the digestive tract, noting the macroscopic features (stomach rugae, plicae circulares, etc.) for correlation with the slides you will also study.

Examine a transverse section of the esophagus. Identify the various layers and sublayers indicated in the general plan.

• Note the epithelial type of the lining,
• The presence of small mucous glands
• Any lymphoid nodules present, and
• Autonomic ganglia and nerves of the myenteric plexus.

What type of muscle do you see in slides of esophagus and what does this tell you about the level from which the biopsy was taken?

Let's consider the muscular layers in more detail.