DepartmentofSurgeryDepartmentofSurgeryRuijinClinicalMedicalCollegeRuijinClinicalMedicalCollegeShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityAnatomyLevatoranimuscleDeepexternalsphincterandPuborectalismuscleConjoinedlongitudinalmuscleSubcutaneousexternalsphincterAnorectalringArterialsupplyoftherectum•Superiorrectalartery•Middlerectalartery•InferiorrectalarteryVenousdrainageoftherectum•Internalhemorrhoidalplexus•ExternalhemorrhoidalplexusSensoryComponentsNeuropathways•Sympathetic+parasympatheticpathwaystointernalsphincter(hypogastric)•Somatictoexternalsphincter(pudendal)SphincterfactorsBasaltone•Pressurezone•analcanal25–120mmHg•rectum5–20mmHg•Continuoustoneofint
andext
sphincterincreaseswithincreasedabdominalpressureMechanismofAnalContinenceStructuralconsiderations•Anorectalanglebetween