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Applied Anatomy and Physiology
The pelvic floor and anal sphincter
STP- BALLARI
www.suyajna.com
Perineal membrane Lien KC et al 2004
Pelvic floor
Pubococcygeus
Iliococcygeus
Coccygeus
Puborectalis
Computer model of levator ani muscle bands DeLancey JOL 2005
Early and late second stage of labour
Translabial ultrasound
Levator avulsion injury Dietz HP et al 2007
Acute intrapartum injury
Muscles cut during episiotomy
Anal Sphincter Anatomy The riddle of the sphincters
Anatomy of the anal sphincter
Anal Endosonography
Inside transducer; Walls of transducer; Subepithelium; Internal Sphincter; LM; External Sphincter
EAS
I
External anal sphincter defect
3 D anal endosonography
external sphincter defect
The Pudendal Nerve
The Pudendal Nerve
Anorectal Physiology
Anal Continence
Neurological Function Rectal Compliance
Sphincter Mechanism Stool Consistency
Mechanism of anal incontinence
IAS relaxation
Contact & Sampling
Inconvenien
t
Convenient
Rectal distension
EAS & Puborectalis
relaxation EAS & Puborectalis
contraction
Colonic accommodation Bowel evacuation
External anal sphincter
• Striated muscle in a state of tonic contraction • Innervated by pudendal nerve • Contributes up to 30% of resting pressure • Responsible for squeeze pressure
Mechanism of anal incontinence
IAS relaxation
Contact & Sampling
Inconvenien
t
Rectal distension
EAS & Puborectalis
contraction
Colonic accommodation
Recto-anal inhibitory reflex Damage to EAS
Ineffective EAS
contraction
Anal incontinence associated with
urge
Internal anal sphincter
• Smooth muscle • Autonomic - myenteric and gut wall plexuses • Contributes up to 70% of resting pressure • Passive soiling and flatus incontinence
IAS injury
Reduced anal tone
Passive soiling and flatus incontinence
IAS defect
Anal Incontinence - history
Wide spectrum of symptoms • Urgency • Urge incontinence • Flatus incontinence • Soiling or staining • Incontinence to liquid stool • Incontinence to solid stool
Anorectal Physiology
Factors necessary to maintain continence • Anal sphincter integrity • Muscle function • Neural connections
The Pudendal Nerve
Pudendal Nerve Terminal Motor Latency
EMG - Reinnervation
normal abnormal
Summary
• Good understanding of perineal anatomy • Physiology → pathophysiology • No single tests gives a definitive diagnosis • Investigations are complementary • Anal endosonography is now the gold
standard investigation of faecal incontinence
