This is because the body in many cases is seen as pure where as the outside world is not. Therefore, parts of the body that allow the outside world in or allow elements inside the body out, are seen and used as an exaggeration of the grotesque. In the article, "Absurdity and Hidden Truth: Cunning Intelligence and Grotesque Body Images as Manifestations of the Trickster", Koepping refers back to Bakhtin's statement, "The themes of cursing and of laughter are almost exclusively a subject of the grotesqueness of the body."
This is because in many cases, the body is seen as pure while the outside world is not. Consequently, bodily components that allow interaction between internal and external elements are perceived as exaggerated grotesqueries. In "Absurdity and Hidden Truth: Cunning Intelligence and Grotesque Body Images as Manifestations of the Trickster," Koepping references Bakhtin's assertion, "The themes of cursing and laughter are predominantly associated with the grotesqueness of the body."