part of receives synaptic input from neuron muscle cell SN innervated muscle of A1-7 SN innervated muscle cell of A1-7 2013-01-15T04:36:29Z FBbt:00110213 The classification of muscles in SN, ISN or TN innervated is based not only on innervation, but also orientation (and presumed function), specification pathways during development (wingless dependendence for SN and TN innervated muscles) and the muscle's location in the internal or external layers (although there are exceptions to this) (Landgraf et al., 1997). fly_anatomy.ontology external muscle cell Any muscle cell (FBbt:00005074) that is part of some SN innervated muscle of A1-7 (FBbt:00059128). larval A1-7-innervating SN motor neuron hypodermal muscle cell of A1-7