Structure and ultrastructure of mechanoreceptors at the human musculotendinous junction

The structure and ultrastructure of 122 lamellated corpuscles and 33 Golgi tendon organs (GTO) from adult human musculotendinous junctions were studied by light microscope and electron microscope techniques. One Meissner corpuscle from a human fingertip was examined for comparison. At the musculotendinous junction the axon terminals of the GTO were observed in direct contact with the tendon collagen. The lamellated corpuscles were located in the connective tissue surrounding the musculotendinous junction. The axon terminals of the lamellated corpuscles were separated from the surrounding tissues by the inner core lamellar cell processes and the capsule layers. A great variation in the structure of both types of receptors was observed. The lamellated corpuscles that were found close to the musculotendinous junction and the GTO may respond simultaneously to muscular contraction, thus providing proprioceptive feedback for sensorimotor control from within the tendon and from the tissues surrounding the musculotendinous junction. Mechanoreceptors found in dermis, subcutaneous and deep tissues can be classified into 2 broad groups. This practical morphologic classification is based on the characteristics of the sensory nerve terminals which have been found to be in contact with the surrounding tissue (muscle spindle, GTO) or with the lamellar cell processes (Vater, Pacini, Meissner), rather than the inconsistent features of the entire receptor such as the size, the shape, or the encapsulation.