Light and electron microscopic features of the structure and innervation of the gastro-oesophageal junction of the monkey (Macaca fascicularis).

This study describes the light and electron microscopical features of the gastrooesophageal junction of the monkey (Macaca fascicularis). In longitudinal histological sections, the circular muscle layer at the junction is greatly thickened. This thickening is further demonstrated in a reconstructed model of the whole circular muscle coat and is therefore referred to as a 'sphincter'. Quantitative ultrastructural studies on the circular muscle at the gastro-oesophageal junction or 'sphincter' show denser nerves when compared with the body of the stomach or the pyloro-duodenal junction. Two types of vesiculated axonal profiles are recognised in the circular muscle layer of the stomach in normal animals: round agranular vesicles which measure between 40 and 60 nm and large granular vesicles measuring 80-120 nm. Animals which received 5-hydroxydopamine treatment show, however, in addition, small dense-cored vesicles measuring 30-60 nm. The gastro-oesophageal and the pyloro-duodenal junctions contain more vesiculated axonal profiles than the body of the stomach. Moreover, both junctions show a predominance of axons with granular vesicles when compared with the body of the stomach.