SEM observations of the elastic networks in canine femoral artery.

Scanning electron microscopy was used to study the normal architectural arrangement of elastic tissue in a medium-sized muscular artery. Selective NaOH sonication digestion or formic acid digestion was used to expose and isolate the elastic networks in the femoral arteries of four healthy dogs. The digested segments were neutralized and freeze-dried before mounting for scanning electron microscopy (SEM) observation. The fenestrated internal elastic lamina (IEL) had a smooth surface with scattered regions of the fine elastic fibers that made up lacy networks protruding from the luminal surface. Prominent ellipsoid fenestrae, randomly scattered across the surface, were grouped into small and large sizes based on their mean diameter. The openings of most fenestrae were bridged by elastic fibers to give the fenestrae a sieve-like appearance. Large, transversely oriented, fusiform gaps were randomly scattered along the length of the IEL. These gaps, filled in by an elastic fiber network, sometimes spanned as much as a quarter of the vessel circumference. It is suggested that these gaps represent splits in the IEL that have been repaired. The tunica media contained a complex network of anastomosing elastic fibers and lamellae that were primarily circumferential in orientation. A well-defined external elastic lamina formed a solid sheet at the junction of the tunica media and the tunica adventitia. The tunica adventitia contained 8-10 incomplete lamellae of large, interconnecting, longitudinally oriented fibers. The architecture of the elastic network in canine femoral artery was compared with that previously described in medium-sized canine veins and in the rat femoral artery.