NEET PG Medical – 2016 – Question – 87
Internal anal Sphincter is formed by ?
a) Puborectalis
b) Circular muscles from lower rectum
c) Longitudinal Involuntary muscles
d) None
Show Answer
Correct Answer – B
Ans. is ‘B’ i.e., Circular muscles from lower rectum [Ref BDC 4th/e Vol. H p. 383; Gray’s Anatomy 40thie Chapter 67]
External sphincter is contributed by fibers from puborectalis part of levator ani muscle (in upper most part); superficial transverse perineal muscles anteriorly and anococcygeal raphe posteriorly (in upper third) and anococcygeal ligament (in middle third).
