By Joe Savarese
Perhaps I am the only one out there with this particular problem, but for some reason, I would always confuse the gastrointestinal tract plexuses. Like most miscellaneous Step 1 topics, I remembered the concept well when as I was reviewing it, but give me a week or two during Step 1 studying and those layers became a mess.
So here is my gift to you. Since I created this mnemonic, I have never mixed up these layers.
“Your GI Tract is a MeSS, My’AM”
Me for Meissner’s plexus
S for Submucosal nerve plexus
S for secretion (its function) or submucosal for (its layer)
Second, My’AM (pronounced “ma’am”)
My for Myenteric nerve plexus
A for Auerbach’s plexus
M for motility (its function) or muscularis (its layer)
Notice MeSS is before My’AM in the above sentence, indicating that the submucosal layer comes before the muscularis layer.
Why does it work? It is hard to make an error here as long as you formulate the words MeSS and My’AM properly. This will allow you to automatically associate Myenteric with Auerbach and Meissner with Submucosal.
Clinical Correlation: Hirschsprung Disease
Neonate will have “congenital megacolon” and an empty rectal vault on digital rectal examination. Recall that the disease occurs due to the lack of ganglion cells/enteric nervous plexuses because of failure of neural crest cell migration. Further work-up and diagnosis requires rectal suction biopsy (regular mucosal biopsy cannot be used for diagnosis). Note the submucosal layer is the most superficial layer where the absence of ganglionic cells can be seen on the biopsy. The narrowed aganglionic zone is distal to the dilated colon. Therefore, the loss of the nerve plexuses effectively cause colonic obstruction and defective peristalsis of the rectum and sigmoid colon leading to signs and symptoms that include bilious vomiting, delayed passage of meconium in first 24 to 48 hours of life, and abdominal distention.
Megacolon is most likely found in children that present with Down syndrome, but another minor cause of megacolon is Chagas disease, which can also cause megaesophagus. Currently the leading theory states that Trypanosoma cruzi causes the destruction of Auerbach’s plexus in the walls of the colon leading to the megacolon and/or megaesophagus.
Can you name another disease that may lead to a complication of megacolon? Leave your answer in the comments!