Scanning electron microscope observations also revealed that the subneural apparatuses of the circular muscles consist of cup-like depressions with some junctional folds. In contrast, those of the longitudinal muscles are characterized by gutters with numerous slit-like folds. Although no differences have been observed between the NMJs of the two muscle layers of the mouse esophagus by transmission electron microscopy, it is not certain if this discrepancy is related to species differences.