FIGURE 1.

Distribution of intestinal neural network. Extrinsic sympathetic and parasympathetic nerve fibers enter the whole layer of the intestinal wall to form complex neural networks with intrinsic enteric nervous and EGCs that innervate gastrointestinal epithelial and immune cells. Epitheliums are differentiated from intestinal stem cells, demonstrating enterocytes, endocrine cells, goblet cells, and Paneth cells. Intestinal stromal cells and various immune cells reside in the intestinal wall, the later including macrophages (Mϕs), lymphocytes, mast cells (MCs), dendritic cells (DCs), and innate lymphoid cells (ILCs). Intestinal neural networks regulate intestinal cells, via neurotransmitters (ACh, NE, ATP etc.), neurotrophic factors (GDNF etc.) and receptors (AChR, AR, P2Y4, RET etc.).