Histochemical and ultrastructural features of the developing enteric nervous system of the human foetal small intestine.

The developing enteric nervous system of the human foetus has been analyzed at the 10th and 18th week of gestation with a special reference to the development of nerve-muscle contacts. The myenteric plexus formation was analyzed by means of electron microscopy and on whole-mounts after NADH diaphorase histochemistry. The development of noradrenergic innervation as an extrinsic inhibitory supply was followed by means of a glyoxylic acid-induced fluorescence method. Differentiated neurons and neuroblasts both occurred in myenteric ganglia of the 10- and 18-week-old foetus although the ganglionic neuropil was almost unidentifiable ultrastructurally at the 10th week of gestation but was mature looking at the 18th week. The nerve plexuses connecting the ganglia frequently formed distant and close myoneural contacts. NADH-diaphorase histochemistry revealed that in the 18-week-old human foetus most of the neural perikarya was within the ganglia. Also, at the 18th week of gestation a well-defined fluorescent network was demonstrated within the ganglia, as well as in the internodal segments. On the basis of these observations we concluded that the time between the 10th and 18th week of gestation has paramount importance for both the morphological and functional maturation of the enteric nervous system.