Outer submucous plexus: An intrinsic nerve network involved in both secretory and motility processes in the intestine of large mammals and humans

The architecture of the enteric nerve networks in the gastrointestinal trac t appears to be more complex in large mammals, including humans, than in sm all laboratory animals. At least two distinct ganglionic nerve plexuses cou ld be identified in the submucous layer in the digestive tract of large mam mals. While functionally and morphologically similar neuron populations are found in the intestinal wall of both small and large mammals, significant differences in their topographical organization and neurochemical features may be present. This short review clearly illustrates that the close and ex clusive association, which has been assumed so far between the efferent pat hways of the submucous plexus and regulation of intestinal secretion/absorp tion on the one hand and between the myenteric plexus and regulation of int estinal motility on the other hand, cannot be interpreted that strictly. An attempt has been made to give a brief overview of the current status of th e identification of distinct functional enteric neuronal classes in the gas trointestinal tract of large mammals using the pig and human intestine as r eferences, and to compare these data with the more extensive information ga thered from the guinea-pig intestine. Anat Rec 262:71-78, 2001. (C) 2001 Wi ley-Liss, Inc.