Absence of myenteric ganglion is seen in –
**Core Concept**
Myenteric ganglion is a type of Auerbach's plexus, which is a complex network of nerve fibers and ganglia that plays a crucial role in regulating gastrointestinal motility. The absence of myenteric ganglion leads to a condition characterized by impaired gut movement, resulting in severe gastrointestinal dysfunction.
**Why the Correct Answer is Right**
The absence of myenteric ganglion is a hallmark of Hirschsprung's disease, a congenital disorder that affects the large intestine. This condition is caused by the failure of neural crest cells to migrate and form myenteric ganglia during embryonic development. As a result, the affected segment of the gut is devoid of ganglia, leading to a lack of peristalsis and severe constipation. The affected segment is typically located in the distal colon or rectum.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the absence of myenteric ganglion is not typically associated with Chagas disease, which is caused by the parasite Trypanosoma cruzi.
**Option B:** This option is incorrect because the absence of myenteric ganglion is not a characteristic of celiac disease, which is an autoimmune disorder that affects the small intestine.
**Option C:** This option is incorrect because the absence of myenteric ganglion is not typically associated with Crohn's disease, which is a type of inflammatory bowel disease.
**Clinical Pearl / High-Yield Fact**
Hirschsprung's disease is a classic example of a condition that results from the failure of neural crest cells to migrate during embryonic development. This condition highlights the importance of neural crest cells in the development of the enteric nervous system.
**Correct Answer:** D. Hirschsprung's disease.