Distribution of Muscle Spindles in the Extensor Digitorum and Hallucis Brevis Muscles of the Macaque as Determined by Plastination

Abstract

The structure-function relationships of the macaque extensor digitorum and hallucis brevis muscle (EDB and EHB), the single intrinsic and four-tendoned muscle of the dorsum of the foot, were investigated in the macaque after preparation of samples by two plastination methods, using gelatin and epoxy resin. These preparative methods clearly revealed the muscle fibers, spindles and myelinated axons in the EDB and EHB. In the more medially located two bellies (the medial two bellies of the EDB), the mean relative proportion of red fibers was larger than in the more laterally located two bellies (the lateral belly of the EDB, and the EHB), while those of intermediate and white fibers were smaller than in the more laterally located two bellies. (The difference was significant between some pairs of bellies.) In the more medially located two bellies, the mean cross-sectional area of each type of fiber, namely, the white, intermediate and red fibers, tended to be smaller than in the more laterally located two bellies. (There were significant differences between many pairs of bellies.) The total number of muscle spindles within an EDB and EHB was 15, and larger numbers of muscle spindles were distributed to the medially located two bellies compared to the laterally located two bellies. (There were significant differences between many pairs of bellies.) These results suggest that the more medially located two bellies of the EDB and EHB are adapted to the relatively precise movements of toes, while the more laterally located two bellies are adapted to the prompt extension and abduction that are related to the arboreal habitat of the macaques.

Distribution, Density, and Structure of Muscle Spindles in the Vastus Intermedius and the Peroneus Longus Muscles of Sheep

“…The muscle spindles have been reported to be distributed greatly in the regions that have many slow-twitch-oxidative (SO) and fast-twitch-oxidative-glycolytic (FOG) myofibers, whereas the regions composed mostly of fasttwitch-glycolytic (FG) myofibers possess few muscle spindles in the medial gastrocnemius, plantaris, and tibialis cranialis muscles of the rat (Yellin, 1969) and the flexor carpi radialis muscle of the cat (Gonyea and Ericson, 1977). Similar distribution of the muscle spindle has been shown in the soleus, lateral gastrocnemius (Ariano et al, 1973; Barker and Banks, 1986), peroneus tertius, peroneus brevis, and peroneus longus of the cat (Ariano et al, 1973;Scott and Young, 1987), and the extensor digitorum and hallucis brevis muscles of the macaque (Matsumura and Saito, 1997).…”