Aharinejad S, Böck P, Lametschwandtner A, Franz P, Firbas W
Dept. Micromorphology and Electron Microscopy, Univ. Vienna, Austria.
Scanning Microsc. 1991 Dec;5(4):1091-6.
The microvasculature of the rat lung was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of vascular corrosion casts and tissue sections. Particular emphasis was placed on postcapillary venules, pulmonary venules and small pulmonary veins (small interlobular veins). Casts of lung capillaries appeared inconspicuous with smooth surface. On the casts of pulmonary venules and small pulmonary veins, by contrast, series of narrow annular constrictions, present at regular distances of 20-25 microns, were seen. These constrictions may be drastic, narrowing down the caliber of the vessel up to 50%. In the constrictions the marks of circularly running tubular structures were seen and were interpreted as being caused by circular bands of smooth muscle cells. Tissue sections of the corresponding vascular wall showed the presence of single or grouped smooth muscle cells which regularly formed myoendothelial junctions. These smooth muscle cells are interpreted as sphincters, responsible for the constrictions seen on cast preparations. Axon terminals were not found in spatial relationship to these sphincters. It is suggested that the described venous sphincters are governed by blood-borne and/or endothelium-derived substances and may significantly influence the blood flow.
通过对血管铸型和组织切片进行扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察，研究了大鼠肺的微血管系统。特别关注了毛细血管后微静脉、肺微静脉和小肺静脉（小叶间小静脉）。肺毛细血管铸型表面光滑，不太明显。相比之下，在肺微静脉和小肺静脉的铸型上，可以看到一系列狭窄的环形收缩，它们以20 - 25微米的规则间距出现。这些收缩可能很剧烈，可使血管口径缩小达50%。在收缩处可见呈环状排列的管状结构痕迹，被解释为由平滑肌细胞的环形带所致。相应血管壁的组织切片显示存在单个或成群的平滑肌细胞，它们经常形成肌内皮连接。这些平滑肌细胞被解释为括约肌，负责在铸型标本上看到的收缩。未发现轴突终末与这些括约肌存在空间关系。有人提出，所描述的静脉括约肌受血源性和/或内皮衍生物质的调控，可能会显著影响血流。
