The Nikon MicroscopyU confocal microscopy image gallery was created with a PCM-2000 confocal scanning system interfaced to a Nikon Eclipse E600 upright microscope. Images were recorded in successive z-axis serial sections with C-Imaging Systems software with excitation illumination provided by an argon-ion and/or a helium-neon laser.

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"You are what you eat" may be true, but how the ingested food becomes vital nutrition for the human body depends largely on the digestive system including the small intestine. The small intestine, a convoluted tube, extends from the pyloric narrowing of the stomach for about 20 feet in length as it tapers down to the large intestine. The duodenum, the first of three parts, is the shortest (about 10 inches) and widest of the small intestine.

The small intestine receives the masticated and partially digested food from the stomach and begins the process of absorption of nutrients by the villi. To help move (peristalsis) the digesting matter down the great length of the small intestine, well-developed muscles consisting of an inner circular and an outer longitudinal layer are utilized. Driving these muscles are parasympathetic and sympathetic nerve fibers of the autonomic nervous system. Two ganglionic sites form where the synapses of the parasympathetic fibers meet: the myenteric Auerbach's plexus and the submucosal Meissner's plexus.

Auerbach's plexus lies between the longitudinal (outer muscle layer) and circular muscular (inner) coats of the duodenum. Peristaltic movements of digesting material originate in the muscles (myogenic) and are initiated by local reflexes. The peristaltic reflex can occur without any neural connections to the brain or spinal cord. Stimulation of the sympathetic nerves inhibits movements while parasympathetic stimulation accelerates peristalsis.

Hirschsprung's Disease is a genetic disorder that prevents the propulsion of digesting matter, leading to functional obstruction. The affected segment shows an absence of ganglion cells and presence of enlarged nerve trunks in the Auerbach's and Meissner's plexuses. In a normal digestive tract, the Auerbach's plexus innervates the two smooth muscle layers and the mucous layer. The release of acetylcholine stimulates intestinal contractions while antagonists such as atropine can block its action. Other drugs have been developed that block the action of the ganglia while those that stimulate the sympathetic nerves also inhibit peristalsis.