Morphological analysis of the human tibialis anterior and medial gastrocnemius muscles.

The morphology and nerve innervation patterns of eight tibialis anterior (TA) and medial gastrocnemius (MG) muscles from human cadavers were examined. TA has three distinct partitions, two of which lie posteriorly. The anterior aspect of the muscle has one partition (head A) whose fibers are oriented longitudinally. The posterior partitions possess fibers that course longitudinally (B head) and obliquely (C head). The posterior longitudinal fibers and the anterior longitudinal fibers are divided by an aponeurosis that is continuous with the tendon of insertion. The proximal muscle fibers insert into this aponeurosis and the distal fibers insert into the tendon. The MG is a unipennate muscle. Both TA and MG muscles show variations in innervation patterns among specimens. In light of these findings, partitioning of TA may be based on its architecture.