Innervation, Especially, Sensory Innervation of the Knee-joint and the Motor Organs around it in Early Stage of Human Embryo

Abstract

The general form of the knee joint is already accomplished in the 3rd or 4th month in a human embryo. Its synovial membrane consists of endothelial cell layer, stratum synoviale rich in blood capillaries and stratum fibrosum of close connective tissue. The adiposal bodies before and after the knee-joint are merely composed of loose connective tissue.The articular nerves running from the joint capsule into the synovial tissue are made of many medullated sensory fibres and a small number of unmedullated vegetative fibres. Vegetative fibres also run along the blood vessels. The primary and secondary plexuses said to be found in adult human knee synovialis are not observed.The articular nerves are rather small in number, so that the distribution of sensory fibres in the synovialis is poor, while the vegetative fibres here are much better developed, forming their terminal reticulum particularly conspicuously around the blood vessels.None of the sensory fibres coming into the synovial tissue pass over into the joint nerve bodies and the PACINIAN bodies found in human adult, most of them ending in unbranched and simepl branched terminations, but in rare cases, presumably capsulated simple branched terminations are also found, and the so-called GOLGI-MAZZONI's bodies were demonstrated, although in a very small quantity. In disagreement with the observations by the past researchers, the PACINIAN bodies were found only in a very small number and limited in the surface part of the collagenous tissue surrounding the patella and in the joint capsule. These bodies existed only in small-sized form.Many GOLGI-MAZZONI's bodies were found around the knee-joint. Since the knee-region in a human embryo of the early stage is very small, the localization of these bodies was accurately determined and the highly ideal silver staining I made use of allowed me to investigate the finest details of them with sufficient clarity. These bodies are formed in contact with the periosteum of the bones participating in the formation of the knee-joint. Around the femur, they are poor in development, but in the periostea of the tibia and particularly of the fibula they are found in many places. They are also found in a small number in the front of the patella. Besides, they are found in a small quantity in the joint capsule of the fossa poplitea and in a much larger quantity in the well-developed connective tissue around it.The positions where the GOLGI-MAZZONI's bodies are found in maximum frequency are the connective tissue at the areas where the muscle fibres come in direct contact with the periosteum, especially where the under-leg muscles take their origin, and the intermuscular connective tissue. Their number is rather small at the origins of the mm. plantaris, gastrocnemius and popliteus, but is very large at the origins of the mm. soleus, peronei, tibiales anterior et posterior, and extensor digitorum longus. The bodies are also found in a large quantity in the membrana interossea cruris.A GOLGI-MAZZONI's body is an arcuate cylinder in form. The elongated inner bulb occupies about one-third of the diameter of the body. The ground substance of the inner bulb consists of a liquid substance, and small special nuclei rich in chromatin are seen arranged in one row in periphery. Around the inner bulb is found a considerably thick transparent layer filled with liquid substance, around which are placed the inner circular connective tissue layer consisting of a single circular row of cells with large oval nuclei poor in chromatin and an outer longitudinal connective tissue layer consisting of cells with elongated nuclei arranged in one or two longitdinal rows. A single thick sensory fibre runs through the proximal pole of the body into the inner bulb and proceeds further along the axis to end bluntly gaining somewhat in size near the distal pole.