Question

A two-year-old has been diagnosed with aganglionic megacolon. Explain the anatomical structure that is problematic and why. Using the normal histology picture attached indicate where in the normal photo you should see the missing structure in the patient with aganglionic megacolon. Downloadable colon photo

Answer 1

—The large intestine consists of the enteric nervous system that provides intrinsic signals for contraction and relaxation of the smooth muscle cells in the intestine.

Mucosa Muscularis mucosa Submucosa layer containing meissener's plexus Circular smooth muscle Myenteric plexus at Longitudinal smooth muscle

—The meissener’s plexus present in the submucosal layer of large intestine and myenteric plexus present in the muscularis externa layer between circular and longitudinal muscle layer form the major part of enteric nervous system.
In aganglionic megacolon or Hirschsprung disease, the ganglionic cell of meissner plexus and myenteric plexus fails to migrate and develop. This results in absence of complete or part of meissener plexus and myenteric plexus.

—Due to absence of enteric nervous system the control of muscles of large intestine is disturbed and results in failure to relax the intestinal muscles.

—The muscles of large intestine remains constricted due to effect of extrinsic regulation by nervous system.

—Due to constant constriction of smooth muscles of large intestine and failure to relax passing of stool becomes difficult resulting in constipation.