This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
What does Hirschsprung's disease involve? SELECT ONE. 
Select and explain. 
A. Peptides, B. Bile salts, C. Meissner and Auerbach plexus deficiency, D. Vagus nerve excess
C: Meissner and Auerbach plexus deficiency
Answer: C: Meissner and Auerbach plexus deficiency 
Explanation: In Hirschsprung's disease, there is an absence of myenteric plexus in the upper anal segment (i.e., the most distal portion of the cloaca). In 15%, the myenteric plexus involves only the upper anus; in 70%, the rectum is also involved; and in 15%, part of the colon is also involved. The abnormal segment is contracted; whereas, the dilated bowel is proximal to the diseased segment.