Ultrastructure du fuseau neuro-musculaire chez l'homme

Summary The ultrastructure of the muscle spindles has been studied in human lumbrical muscles. The findings have been compared with the morphology of muscle spindles of rat and sheep examined with light and electron microscopy. The study is based on cross and longitudinal sections of the entire muscle spindle obtained by dissection. The different components of the spindle are described with special reference to the nuclear bag and nuclear chain fibres. These nuclei have been examined in human adult and newborn material and compared to the animal ones. ADN measurements revealed that although there are morphological differences between the two kinds of nuclei in human newborn spindles, the amount of ADN is the same as well in the nuclear bag as in the nuclear chain nuclei. Special attention is also given to the sensory and motor endings in the muscle spindles and to the presence of Pacinian corpuscules in these receptors. Finally two kinds of leptomeric organelles are described in human material.