Morphologic and histochemical characteristics of laryngeal muscle.

Laryngeal muscle (LM) is highly specialized for phonation and sphincter activity. We queried whether this specialization is reflected in the structure of LM. We examined, using histochemical techniques, the structure of five LM from three men who died suddenly and who had no evidence of laryngeal disease. Compared with nonlaryngeal skeletal muscle, our specimens demonstrated moderate fibrosis, rounding of fibers, basophilia, and ragged red fibers that were shown to be mitochondria. In general, LM fibers are smaller, have more variability in size, and contain a greater percentage of histochemically type 1 fibers than limb skeletal muscles. These differences suggest that theories of motor control derived from studies of limb skeletal muscles may not apply to LM.