人胎儿脊髓胶状质发育的电镜观察

用电镜观察１５～４０周人胎儿脊髓胶状质发育的超微结构变化。结果发现，胎儿胶状质神经元核大、核仁明显，胞浆薄、核搪体少；神经毡内无髓纤维最多，有髓纤维稀少。１５周可见有髓纤维，最宽径自１５至３２周增大明显，以后变化不大；１５至４０周髓鞘最厚处的厚度明显地增厚。２４周出现突触。发育中存在轴－树、轴－轴和树－树突触，以轴－树突触最多见。形成突触的轴突和树突各有两种类型。

ELECTROMICR0SCOPIC INVESTIGATIONS OF THE DEVELOPING ULTKASTRUCTURES OF THE SUBSTANTIA GELATINOSA IN THE SPINAL CORD OF HUMAN FETUSES

Electromicroscopic investigations of the developing ultrastructures of thesubstantia gelatinosa in the spinal cord of human fetuses from 15 weeks of menstrual age to 40weeks are reported in this study. The neuron in the substantia gelatinosa of the fetuses has alarge nucleus with prominent nucleolus,but the cytoplasm is thin with a few ribosomes.Most ofthe fibers in the neuropil are unmyelinated, and myelinated fibers are scarce. Myelinated fiberscan be seen at 15 weeks,the widest diameter of the mvelinated fibers increases greatly from 15 to32 weeks,after which not much change can be seen. The thickness of the thickest portion of themyelin sheaths shows a conspicuous increase from 15 to 40 weeks.The development of thesynapses in the substantia gelatinosa appears after that of the myelinated fibers.The synapsesdo not appear until 24 weeks.During the development,axo-dendritic,axo-axonic anddendro-dendritic synapses can be observed;among which the axo-dendritic synapses are mostabundant.The axons and dendrites which form synapses have two separate types respectively.