[Evaluation of cartilaginous wrist development in the human during the prenatal period]

The aim of the work was to assess the development of human chondral wrist in the prenatal period with regard to cartilaginous buds topography, histologic structure and development of article fissures in each month of intrauterine life. The performed examination covered 89 fetuses from 2nd to 9th month of prenatal life. Altogether 178 wrists were examined. The age of the fetuses was estimated on the clinical data, body mass, and crown-rump length base. Fetuses with developmental anomalies were excluded. At the beginning the material for microscopy was fixed and decalcified, next it was embedded in paraffin and cut on the microtome in a frontal plane. Preparations were stained by Van Gieson method, hematoxylin, and eosin. They were microscopied. I found that most of 2 month-old fetuses had 8 wrist bones buds. They were arranged in two rows: proximal and distal. Some of the examined fetuses had accessory bud that joined navicular bone during development process. Occasionally, 3, 4, 5, and 6 month-old fetuses revealed one chondral element with 2 or 3 differentiation foci in place of navicular, lunar and triangular bones. I disclosed no differences in histological development of wrist bone buds. (Fig. 1-4). There was a layer of thickened cells with mitotic figures at buds periphery in 2 and 3 month-old fetuses. A large amount of intercellular substance was in the central part. A reduced density of cells was seen in peripheral parts as well as in central parts, being viewed in intercellular substance, of buds in the 4th month of intrauterine life. Plane mesenchymal cells were observed on the surface of the buds, they created tracts forming layers, which may correspond to synovial membrane structure. The homogeneous substance staining yellow by Van Gieson method, what may be synovial membrane secretion, was found in 5 month-old fetuses. Reduction of cells from the periphery of buds had continued in 6th month. Cells forming buds resembled chondral, had light cytoplasm and central karyon, and fell into pairs. During further evolution it was observed that there was an increase of intracellular substance, formation of pairs and groups of chondral cells up to high differentiation. In 8th and 9th month of intrauterine life cells appeared like mature hyaline cartilage. Also chondral canaliculi including blood vessels were detected in the buds. Article fissures forming processes were observed already from 2nd month of intrauterine life and terminated their action in 5th month in the majority of fetuses. The evolution of distal radioulnar articular disc was seen, too. Mesenchyma being rich in cells was not differentiated in 2 month-old fetuses but during the evolution it changed into connective tissue band adhering to styloid process of ulna from one side and to head of radius from the other. Among forming article discs connective tissue fibres were found to be typical of chondral cells in 7, 8 and 9 month-old fetuses.