system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Rectal incontinence is due to involvement of :a) External anal sphincterb) Internal anal sphincterc) Ischiococcygeusd) Pubococcygeus
assistant
The correct answer is  Rectal continence depends solely on the anorectal ring and any damage to this ring results in rectal incontinence.
The anorectal ring is a muscular ring present at the anorectal junction, and formed by the fusion of -

Puborectalis (a part of pubococcygeus which in turn is a part of levator ani)
Deep external anal sphincter
Internal anal sphincter

The puborectalis muscle appears to be the most important muscle for maintaining fecal continence.