Light microscopy of the large bowel (colon) showing its internal epithelial surface (part of the mucosa), the deeper submucosal, and the wide double-layered smooth muscle called the muscularis externa. The epithelium has many intestinal crypts which are simple tubular glands with goblet cells producing mucus, and enterocytes extracting fluid from the lumen to desiccate fecal material. The muscle layers provide peristaltic contractions to compact and move waste materials towards the rectum. Colonic contractions of the muscle is largely controlled by an intrinsic nerve supply called the myenteric or Auerbach's plexus. The nerve cells bodies (ganglia) of the plexus are seen as pale islands between the inner and outer muscle layers. Magnification x45 when printed at 10 cm.