Observations on the histology and histochemistry of the oesophagus of the perch, Perca fluviatilis L.

The anatomy and enzyme histœhemistry of the œsophagus of a freshwater teleost perch ( Perca fluviatilis L.) has been studied. The mucosa is composed of an undifferentiated layer of basal epithelial cells, mucous cells and surface epithelial cells. The submucosa is compact and contains blood vessels, nerves and bundles of striated longitudinal muscles. The outer circular muscular layer contains both striated and smooth muscle fibres. Electron microscopy shows that the surface epithelial cells are degenerative and that they surround and support pores of the mucous cells. Undifferentiated epithelial cells undergo cytoplasmic changes and eventually become surface epithelial cells. Mucous cells arise from the undifferentiated epithelial cells and their droplets contain acid and neutral mucosubstances. Alkaline phosphatase, non-specific carboxylic esterases and aminopeptidase activity is absent in the mucosa. However, acid phosphatase activity is localized in the surface epithelial cells.