胎児関節軟骨の発育に伴う変化
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概要
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The cartilage of 33 embryos in week 12 to 40 of gestation were examined using a scanning electron microscope and the growth process of the surface of the articular cartilage and of the structure of the laminar surface were observed. The results are as follows : (1) No great difference in the process of development was observed between the surface of the articular cartilage in the femur, humerus and talus or the articular cartilaginous laminar surface. In all the joints, there was no great structural difference. The surface of the articular cartilage in the 12-week-old embryo exhibited a prominence with a definite directional development ; in the 15-week-old embryo, this prominence became even greater. From about week 20 of gestation, the appearance of collagen fibre was noted, to attain mature development, join together and form bundles of fibre. In week 40 of fetal development, the surface of fetal articular cartilage showed almost the same surface structure as seen in adults. This surface structure was observed to be composed of collagen fibre with a definite directional development and collagen fibrillae, and these were beginning to collect into bundles of fibre and form indentations comprising the articular surface. (2) In the divided surface of the articular cartilage in the 12-week-old embryo, the surface layer consisted of membranous structure, and the lower layer consisted of densely packed chondrocytes, thus forming two distinct layers. Here, also, ground substance was observed in the cartilage thought to be undergoing ossification. During week 15 of gestation, 3 layers were observed, including the surface layer, transverse layer and the layer directly below within the ground substance where the chondrocytes were densely packed. In the deep layer, the space between the chondrocytes in the ground substance was very small. In the 20-week-old fetus the surface layer became thinner, and the layer below with the transverse fibre bundles became thicker. In the next lower layer, the intercellular interval widened slightly in the cartilage matrix. At week 40 of gestation, the surface layer thinned out and it became indistinguishable from the next lower layer with the bundles of fibre which increased in width and the intercellular interval directly below became even wider. (3) If the surface structure and the laminar structure are considered, the joint during the growth process begins to resemble the articular cartilage of adults at week 40 of gestation.
- 学校法人 昭和大学・昭和医学会の論文