Pelvic Floor AnatomyPelvic Floor Anatomy

Colorectal ConferenceColorectal Conference

7/21/057/21/05

Peter M. Kaye, M.D.Peter M. Kaye, M.D.

The Pelvic FloorThe Pelvic Floor

Musculotendinous Musculotendinous hammock or slinghammock or sling

Termination of the Termination of the pelvic outletpelvic outlet

Muscles of the pelvisMuscles of the pelvis Anal sphincter complexAnal sphincter complex Levator ani musclesLevator ani muscles

Support the abdominal Support the abdominal and pelvic organsand pelvic organs

Connect the pelvis to Connect the pelvis to the vertebral columnthe vertebral column

Maintain continenceMaintain continence

Anal Sphincter ComplexAnal Sphincter Complex

Internal anal sphincterInternal anal sphincter Conjoined longitudinal muscleConjoined longitudinal muscle External anal sphincterExternal anal sphincter

Internal Anal SphincterInternal Anal Sphincter

Extension of the circular muscle Extension of the circular muscle layer of the rectumlayer of the rectum

Constant maximal contractionConstant maximal contraction 50-85% of resting anal tone 50-85% of resting anal tone Autonomic innervationAutonomic innervation

Parasympathetic…..S2-4Parasympathetic…..S2-4 Sympathetic……..thoracolumbar Sympathetic……..thoracolumbar

ganglia (L5)ganglia (L5) Suggested that both Suggested that both

parasympathetic and parasympathetic and sympathetic innervation cause sympathetic innervation cause inhibition of contractioninhibition of contraction

Conjoined Longitudinal Conjoined Longitudinal MuscleMuscle

Extension of the Extension of the longitudinal muscle longitudinal muscle layer of the rectum, layer of the rectum, along with levator ani along with levator ani muscle fibersmuscle fibers

Structural support, Structural support, anchoring the anchoring the anorectum to the anorectum to the pelvispelvis

External Anal SphincterExternal Anal Sphincter

Multiple layers of Multiple layers of striated musclestriated muscle

Voluntary contractions Voluntary contractions to prevent fecal leakto prevent fecal leak

25-30% of resting anal 25-30% of resting anal tonetone

Somatic innervation Somatic innervation from the inferior rectal from the inferior rectal branch of the pudendal branch of the pudendal nerve (S2-3) and the nerve (S2-3) and the perineal branch of S4perineal branch of S4

Levator Ani MusclesLevator Ani Muscles

PubococcygeusPubococcygeus IliococcygeusIliococcygeus PuborectalisPuborectalis IschiococcygeusIschiococcygeus

PuborectalisPuborectalis

U-shaped, medial U-shaped, medial most located levator most located levator ani muscleani muscle

Pulls the anorectal Pulls the anorectal junction anteriorly, junction anteriorly, forming the forming the anorectal angleanorectal angle

Pelvic floor muscle Pelvic floor muscle vs. sphincter vs. sphincter muscle?muscle?

Functional AnatomyFunctional Anatomy

Puborectalis and the anorectal angle allow Puborectalis and the anorectal angle allow for gross fecal continencefor gross fecal continence

Relieves pressure from the sphincter Relieves pressure from the sphincter processprocess

The sphinter complex is responsible for The sphinter complex is responsible for gas and liquid continencegas and liquid continence

DefecationDefecation Relaxation of the puborectalisRelaxation of the puborectalis Contraction of the other levator musclesContraction of the other levator muscles

Functional AnatomyFunctional Anatomy

Rectal prolapseRectal prolapse Laxity in sphincter Laxity in sphincter

complex and complex and levator muscleslevator muscles