#musculus_sphincter_ani_internus  an internal ring of smooth muscle formed by circular fibers of the rectum
  supertype:  involuntary_muscle__involuntarymuscle__smooth_muscle  a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)
  part of:  anal_sphincter__sphincter_ani__sphincterani__musculus_sphincter_ani  the sphincter muscle of the anus
     part of:  anus__arse__arsehole__asshole  excretory opening at the end of the alimentary canal
        part of:  rectum  the terminal section of the alimentary canal; from the sigmoid flexure to the anus
           part of:  large_intestine__largeintestine  beginning with the cecum and ending with the rectum; includes the cecum and the colon and the rectum; extracts moisture from food residues which are later excreted as feces
              part of:  alimentary_canal__alimentary_tract__digestive_tube__digestivetube__digestivetract__gastrointestinal_tract__GI_tract  tubular passage of mucous membrane and muscle extending about 8.3 meters from mouth to anus; functions in digestion and elimination
                 part of:  digestive_system__digestivesystem__gastrointestinal_system__systema_alimentarium__systemaalimentarium__systema_digestorium__systemadigestorium  the system that makes food absorbable into the body
                    part of:  body__organic_structure__organicstructure__physical_structure  the entire physical structure of an organism (especially an animal or human being); "he felt as if his whole body were on fire"

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