人胎儿圆窗膜超微结构的观察

本研究用透射电镜观察16侧第4～9个月胎儿圆窗膜的超微结构。圆窗膜分3层:1.外上皮层面对鼓室,为鳞状上皮,4个月胎儿无上皮层;2.中层为结缔组织;3.内层面对鼓阶,由间皮细胞组成。随着胎龄增加,上皮层变薄;成纤维细胞转变为纤维细胞;胶原纤维和弹力纤维明显增多。8个月胎儿圆窗膜基本上具有成人的形态结构,起屏障作用,阻止鼓室内物质任意经过圆窗膜;具有抗压力以及作为外淋巴缓冲结构等重要听觉生理功能。

ULTRASTRUCTURE OF THE ROUND WINDOW MEMBRANE IN HUMAN FETUS

The normal round window membrane in human fetus was examined by transmission electron microscopy. The membranes in 5 to 9 months old fetus consist of the following three layers: (1) an outer squamous epithelial layer facing the middle ear, there was no epithelium in 4-month-old stage, (2) a middle fibrous layer consists of collagenous and elastic fibrils, fibroblasts, fibrocytes, blood vessels, and nerves, (3) an inner layer of simple flat cell(mesothelial cell) facing the scala tympani. With the advance of age the epithelium is getting thinner, the number of fibroblasts is reduced but that of fibrocytes is increased, collagenous and elastic fibrils grow gradually in density.The round window membrane in 8-month-old fetus is simillar to the ultrastrucrural characteristics of that in adult. The round window membrane has an important and complicated physiological function. The epithelium of the tympanic layer with tight junction and many desmosomes appear to present a barrier to free diffusion through the intact membrane. The stability and elasticity of the membrane provide protection against rupture and elasticity plays a role in the physiology of hearing as well.