Parra S C, Gaddy L R, Takaro T
Lab Invest. 1978 Jan;38(1):8-13.
Normal canine lungs were prepared for ultrastructural studies using two different routes for fixation: the airways route and the vascular route. Using the airways route, under conditions of controlled pressure, scanning and transmission electron microscopic studies of alveolar surfaces allowed identification of an average of 19 alveolar pores per exposed alveolar surface, each pore averaging approximately 3 micron. in diameter. The alveolar surface was honeycombed in appearance, with the walls of multiple capillaries bulging into the alveolar space. Using the other route, vascular perfusion of the lungs with the fixative and controlling pressures in both the vascular and airway compartments, scanning electron microscopic studies showed that most exposed alveoli exhibited a smooth or slightly wrinkled surface, essentially devoid of pores and averaging only three pores per alveolus. By transmission electron microscopy, alveolar surfaces were found to be covered with an extracellular material suggestive of lung surfactant; alveolar pores, averaging approximately 1 micron. in diameter, were filled with the same material. It is concluded that most alveolar pores of normal dogs are bridged by and filled with lung surfactant. These findings can be demonstrated most reliably by using vascular perfusion of the lungs for introducing the fixative.
气道途径和血管途径。采用气道途径，在控制压力的条件下，对肺泡表面进行扫描和透射电子显微镜研究发现，每个暴露的肺泡表面平均有19个肺泡孔，每个孔的平均直径约为3微米。肺泡表面呈蜂窝状，多个毛细血管壁向肺泡腔内凸起。采用另一种途径，即向肺内血管灌注固定剂并控制血管和气道腔室的压力，扫描电子显微镜研究显示，大多数暴露的肺泡表面光滑或略有皱纹，基本没有孔，每个肺泡平均只有三个孔。通过透射电子显微镜观察，发现肺泡表面覆盖有提示肺表面活性物质的细胞外物质；平均直径约为1微米的肺泡孔充满了相同的物质。得出的结论是，正常犬的大多数肺泡孔被肺表面活性物质桥接并充满。通过对肺进行血管灌注以引入固定剂，能够最可靠地证明这些发现。
