Background: The manner of innervation of the muscles of the inferior limb, pelvic outlet, and tail in rhesus monkey (Macaca mulatta) was investigated in detail in 11 pelvic halves of four males and two females.
Results: The origins of the pudendal nerve were widespread and overlapped the sacral plexus. After removal of the bone structures, detailed dissection revealed the origin of the pudendal nerve to ventrocaudally overlap the sacral plexus. This dorsoventral branching pattern between the sacral plexus and the pudendal nerve is similar to that in Urodela (Akita, 1992b), Lacertilia (Akita, 1992a) and Aves (Akita et al., 1992a), and is a basis for morphological understanding of the muscles of the pelvic outlet.
Conclusions: The muscles of the pelvic outlet consist of the levator, sphincter, and tail muscle groups, based on the stratification of the supplying nerves the former two groups likely derive from the ventral muscles of the inferior limb, and the latter group from the ventral caudal (trunk) muscles.