Palisade endings in human extraocular muscles.

The presence of nerve terminals in the tendinous insertions of human eye muscles was investigated histologically in adult human eye muscles obtained from donor eyes and in muscle pieces resected from juvenile patients undergoing surgical correction for strabismus. Lateral and medial recti, superior and inferior oblique muscles from adults, were stained "en bloc" using a silver impregnation method. Numbers of nerve terminals were isolated that resembled "palisade endings" previously described in other species. A single palisade ending usually appeared as an interwoven network of fine neural filaments that cupped the inserting tip of a single extrafusal fiber. A collection of palisade endings on several neighboring muscle fibers were supplied by a single myelinated axon that branched from a nerve bundle in the muscle mass. The presence of nerve terminals at the distal musculotendinous interface of juvenile muscle also was observed when some resected specimens of lateral and medial recti were sectioned and stained using Holmes' silver method with a picrofuschin counterstain. No conventional Golgi tendon organs were seen.