Anatomical partitioning of three multiarticular human muscles.

To examine neuromuscular partitioning within human muscles, the innervation patterns and muscle fiber architecture of the flexor carpi radialis (FCR), extensor carpi radialis longus (ECRL) and lateral gastrocnemius (LG) muscles were examined. Consistent patterns of innervation between specimens were found within each of the three muscles. The nerve to the FCR clearly innervates three major architectural divisions of the muscle. The ECRL is innervated by two different muscle nerves. Branches of these nerves innervate at least two distinct anatomical subvolumes. However, the subvolumes of the ECRL defined by muscle architecture are not totally congruent with those defined by the innervation pattern. In the LG, the single muscle nerve branches into two main divisions, and these subsequently divide into branches which supply the three heads. However, each head does not receive a completely private nerve. These results indicate that human muscles are partitioned in a manner roughly similar to the divisions of the same muscles in cats and rats, but with less congruency of architecture and innervation.