The internal anal sphincter is a thickened continuation of which layer of the rectal wall?

• A Longitudinal muscle layer
• B Serosa
• C Mucosa
• D Circular muscle layer ✓

Explanation

The internal anal sphincter is a thickened downward continuation of the circular smooth muscle layer of the rectum. It is involuntary and extends from the anorectal junction to just above the intersphincteric groove. The longitudinal muscle layer continues as the conjoint longitudinal coat. Mucosa and serosa are not muscular layers and do not form the sphincter.

Reference: Gray's Anatomy, 41st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.