The distribution of serotonin-containing cells in the human alimentary tract.

The distribution of serotonin-containing cells (SC cells) in the human alimentary tract was studied by means of the fluorescent histochemical method of Falck et al. on surgically resected specimens. No SC cells could be observed in the nonmucosal parts of the alimentary tract and in the squamous cell epithelium of the esophagus. The richest SC cells were observed in the upper portion of the small intestine (namely the duodenum and the jejunum). The rectum was relatively rich in the distribution of SC cells. They moderately distributed in the terminal ileum and the pyloric and cardiac gland region of the stomach. The ascending, transverse, descending and sigmoid colon and the fundic gland region of the stomach showed poor distribution of SC cells. The basal-layer of the mucosa contained generally richer SC cells than the superficial-layer of the mucosa throughout the alimentary tract except for the esophagus. In the pyloric gland region of the stomach, the rectum and the upper portion of the small intestine, often a few SC cells were observed in the basal part of several glands in the transverse section. In contrast, SC cells could be rarely identified in other parts of the alimentary tract even in the basal part of the mucosa. And it was characteristic that SC cells distributed fairly even in the mucosa of the sigmoid colon.