Komuro T, Hashimoto Y
Department of Anatomy, Ehime University School of Medicine, Japan.
Arch Histol Cytol. 1990 Mar;53(1):1-21. doi: 10.1679/aohc.53.1.
The three-dimensional organization of the mucosa and submucosa of the rat intestine was analysed by scanning electron microscopy (SEM) aided by micro-dissection methods. New functional aspects raised by the SEM observations were examined by transmission electron microscopy (TEM). Morphogenesis of the intestinal villi was also illustrated three dimensionally. Removal of the epithelium by osmic acid maceration revealed the presence of many round fenestrations averaging 3 microns in diameter over the villous basal lamina. TEM confirmed that they were not artifacts but represented passages or tracks of cells of the immune system such as lymphocytes, eosinophils and macrophages. Penetration of the epithelial processes into the lamina propria was also observed. Close contacts between these free cells and the epithelial cells suggest an intercellular communication between these different cell types. The basal lamina is thus appears as a structure that allows dynamic interaction between the epithelial layer and the lamina propria, though it is generally regarded as a rigid structure acting as a barrier. Beneath the basal lamina, a cellular reticulum of fibroblast-like cells overlies the capillary network in the villi. These cells are characterized by bundles of actin filaments and contact with each other by gap junctions. This cellular reticulum probably influences the absorption of nutrients from the villi by its contractile ability in addition to its supportive role. A similar cellular network occurs beneath the epithelium of the intestinal glands. These cells may also mechanically support the glandular organization, maintaining the delicate microvascular bed. The submucosa is considered the skeleton of the intestine. SEM reveals the main framework of the submucosa is as being composed of two sets of collagen fibers running diagonally around the intestinal wall, one set in a clockwise direction, the other, counterclockwise. These fibers--in different arrays--interweave to form a lattice sheet, which presumably provides the tissue with a high resistance to mechanical forces, particularly in respect to radial forces. The diagonal orientation of the collagen fibers is essential for the flexibility of the submucosa in allowing deformation of the intestinal wall during peristalsis. Despite the nonelastic nature of the collagen fibers, the submucosa can adapt to the various shapes of the intestinal lumen by simply changing the angles formed by these fibers. Structures of the villous microcirculation, the muscularis mucosae and of the submucous plexus are also discussed.
采用显微解剖方法辅助扫描电子显微镜（SEM）分析大鼠肠道黏膜和黏膜下层的三维组织结构。通过透射电子显微镜（TEM）研究SEM观察结果所揭示的新功能方面。还对肠绒毛的形态发生进行了三维展示。通过锇酸浸蚀去除上皮后发现，在绒毛基膜上存在许多平均直径为3微米的圆形窗孔。TEM证实这些并非人为假象，而是代表免疫系统细胞（如淋巴细胞、嗜酸性粒细胞和巨噬细胞）的通道或轨迹。还观察到上皮突起穿透进入固有层。这些游离细胞与上皮细胞之间的紧密接触表明这些不同细胞类型之间存在细胞间通讯。因此，基膜似乎是一种允许上皮层与固有层之间进行动态相互作用的结构，尽管它通常被视为一种起屏障作用的刚性结构。在基膜下方，成纤维细胞样细胞的细胞网络覆盖在绒毛中的毛细血管网络上。这些细胞的特征是有肌动蛋白丝束，并通过缝隙连接相互接触。除了起支持作用外，这个细胞网络可能还通过其收缩能力影响绒毛对营养物质的吸收。在肠腺上皮下方也出现类似的细胞网络。这些细胞也可能在机械上支持腺体组织，维持精细的微血管床。黏膜下层被认为是肠道的骨架。SEM显示黏膜下层的主要框架由两组围绕肠壁对角排列的胶原纤维组成，一组呈顺时针方向，另一组呈逆时针方向。这些纤维以不同的排列方式相互交织形成一个格子状薄片，大概为组织提供了对机械力的高抗性，特别是在径向力方面。胶原纤维的对角排列对于黏膜下层在蠕动过程中允许肠壁变形的灵活性至关重要。尽管胶原纤维具有非弹性性质，但黏膜下层可以通过简单改变这些纤维形成的角度来适应肠腔的各种形状。还讨论了绒毛微循环、黏膜肌层和黏膜下神经丛的结构。
