A scanning electron microscope study on the autonomic groundplexus in the lamina propria mucosae of the guinea-pig small intestine.

The occurrence and fine structure of the autonomic groundplexus in the lamina propria mucosae of the guinea-pig small intestine were studied by scanning electron microscopy after removing connective tissue elements by maceration in hydrochloric acid. Transmission electron microscopy was also performed to investigate the fine structure of the neuronal and glial elements in the autonomic groundplexus. Nerve fasciculi consisting of neuronal processes and enteroglial cell sheaths formed a three-dimensional network intercalated between blood and lymph vessels. Processes of enteric neurons ran within the enteroglial cell framework. No blind ends of nerve fasciculi were found. Terminal varicosities of neuronal processes were frequently exposed on the surface of the nerve fasciculi. The locations of these naked varicosities may represent the sites of interaction between the enteric neurons and their target tissues.