The accessory phrenic nerve in the rat

Summary Reinnervation studies of the diaphragm led us to reinvestigate the normal anatomy of the phrenic nerve of the rat. The phrenic nerve originates from the cervical nerve roots C₄ and C₅. In 16 out of 19 normal rats an accessory phrenic nerve was observed receiving its segmental fibres from C₆. The number of myelinated axons of the accessory phrenic nerve varied from 41 to 101 (mean: 64.3, i.e. about 15% of the average number of axons in the common phrenic nerve). The accessory phrenic nerve innervates the dorsal part of the costal and the lateral part of the crural region, whereas the remaining parts of the hemidiaphragm are supplied by the segments C₄ and C₅. There is no evidence for any additional contribution to the motor innervation of the diaphragm from intercostal nerves.Direktor: Prof. Dr. W. ZenkerThis study was supported by the Fonds zur Förderung der wissenschaftlichen Forschung in Österreich.