Kalmar "bakin reshe" tana nufin kowane jerin nau'ikan kasusuwa guda biyu ko kasusuwa na cartilaginous a cikin amfrayo na kashin baya wanda ke goyan bayan gills ko pharyngeal slits. Ana kuma kiran waɗannan arches a wasu lokuta a matsayin " arches na pharyngeal "ko" arches visceral ". Siffa ce mai mahimmanci wajen haɓaka fuska, wuya, da makogwaro, kuma suna haifar da nau'ikan sifofi daban-daban a cikin kwayoyin halittar manya, gami da ƙasusuwa da tsokoki na muƙamuƙi, kunne na tsakiya, da makogwaro. A cikin mutane, ƙwanƙolin reshe suna taka muhimmiyar rawa wajen samuwar fuska da wuya a lokacin ci gaban amfrayo.