The number and distribution of muscle spindles in human intrinsic postvertebral muscles

Abstract

Because of the possible involvement of the postvertebral muscles in these intricate functions of the body, their patterns of innervation and control need to be clarified. Detailed information of motor supply is scanty, and attempts to determine segmental distributions have not been encouraging. The literature on the incidence of sensory receptors, including muscle spindles, is incomplete. Gregor (1904) reported on a quantitative study of muscle spindles in some intrinsic postvertebral muscles of a 26 cm human fetus, but his specimen was incomplete. Detailed quantitative studies of human muscle spindles have also been made by Voss (1956) in anterior muscles of the neck, trapezius and latissimus dorsi; by Voss (1958, 1959) in suboccipital and ventral abdominal muscles, and by Cooper & Daniel (1963) in suboccipital muscles. Cooper (1960, 1966) summarised an extensive series of reports by Voss and his co-workers on the distribution of spindles in human limb, trunk and cranial muscles. There appears to be no information on the segmental distribution of muscle spindles in the posterior muscles of the trunk. The present study is mainly concerned with the number and distribution of muscle spindles.