Editing Incontinence (section)

=== '''Rectal/anal     sensation''' ===

** Pudendal nerve (S2, 3, 4)      innervates EAS
** Pelvic branches (S3 and 4)      innervate puborectalis
** Rectal distension is      transmitted along S2, 3, 4 PNS nerves
** Recto-anal inhibitory reflex      - when distended with stool, the internal sphincter relaxes, followed by      reflexive contraction of EAS, creating a sensation of urgency. This is      followed by pelvic floor relaxing, decreasing acuity of ano-rectal angle,      and defecation (if appropriate). Voluntary contraction of the pelvic      floor and EAS causes the sensation of urgency to subside as the rectum      accommodates.
** Anal sampling - as the IAS      relaxes, a small amount of stool can be 'sampled' and moved down to anus,      allowing for differentiation of gas and solid stool.