A 6-year-old girl comes to her pediatrician with constipation, abdominal distention, and vomiting. After thorough examination, she is diagnosed as having Hirschsprung disease (aganglionic megacolon), which is a congenital disease and leads to dilation of the colon. This condition is caused by an absence of which of the following kinds of neural cell bodies?

**Core Concept**
Hirschsprung disease is a congenital disorder characterized by the absence of ganglion cells in the distal colon, leading to a functional obstruction. This absence disrupts the normal neural control of the colon, resulting in a failure to relax the affected segment of the colon and subsequent dilation.

**Why the Correct Answer is Right**
The correct answer is related to the absence of neural cell bodies, specifically the ganglion cells, in the submucosal and myenteric plexuses of the colon. These ganglion cells are responsible for the neural control of the colon, including the regulation of peristalsis and relaxation of the intestinal smooth muscle. In Hirschsprung disease, the absence of these ganglion cells leads to a failure of the colon to relax, resulting in a functional obstruction and the characteristic symptoms of constipation, abdominal distention, and vomiting.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically refer to the neural cells responsible for the symptoms of Hirschsprung disease.

**Option B:** This option is incorrect because it refers to the type of muscle found in the wall of the intestine, but it is not directly related to the neural control of the colon.

**Option C:** This option is incorrect because it refers to the type of connective tissue found in the wall of the intestine, but it is not directly related to the neural control of the colon.

**Clinical Pearl / High-Yield Fact**
The absence of ganglion cells in Hirschsprung disease is a result of a mutation in the RET proto-oncogene, which is involved in the development of the enteric nervous system. This is an important fact to remember for exams, as it highlights the genetic basis of the disease.

**Correct Answer:** C. Enteric neurons

✓ Correct Answer: D. Parasympathetic postganglionic neuron cell bodies