Distribution of intramuscular nerves in the human diaphragm

Objective: To investigate the distribution and the features of the branches of intramuscular nerves of the human diaphragm. Methods: Modified Sihler's neural staining technique was used to observe the nerve branches of diaphragms. Results: (1) Each phrenic nerve trunk was divided into 3-4 primary branches after penetrating the diaphragms. One(anterior branch) run forward and innervated sternal region.One or two (anterior-lateral branch) run laterally and innervated costal region. Last one (posterior branch) run backwards and subdivided into 2 second branches, and innervated posterior costal and crus region respectively. The terminal branches arranged in the middle of muscle bundles of diaphragm and formed a intensive horizontal kidney-shaped nerve plexus. (2) The branches of one side phrenic nerve did not across midline and extend into the other side. (3) The branches of intercostal nerves were not found in the fringe of costal region of diaphragm in 2 specimens including the lower intercostal muscles. Conclusions: (1) Phrenic nerve innervate diaphragm, and there are no overlaped and dominant innervations.(2) The terminal branches of phrenic nerve arrange in the middle of muscle bundles of diaphragm and form a denser horizontal kidney-shaped nerve plexus.