Muscle spindles in the human levator veli palatini and palatoglossus muscles.

Muscle spindles are present in many muscles of the speech mechanism including those of the jaw, tongue, larynx, and respiratory system. Past investigations that have examined muscles of the velopharynx for the presence of muscle spindles have reported their existence only in the tensor veli palatini and palatoglossus muscles. The present investigation has demonstrated the existence of muscle spindles in two muscles of the human velopharynx--the levator veli palatini (LVP) and palatoglossus muscles. Seven LVP and two palatoglossus muscles were embedded in paraffin blocks, serially sectioned at 8 microns, and selected slides were stained by a modified Gomori trichrome technique. Scanning by light microscopy at 40x revealed spindles in all of the muscles examined. This positive finding likely reflects the use of a more chromatically distinctive staining procedure and a higher scanning magnification than were used in prior investigations. The potential roles of muscle spindles in velopharyngeal function are addressed.