ELASTIC FIBER SYSTEM OF THE FEMALE CANINE URETHRA - HISTOCHEMICAL IDENTIFICATION OF ELASTIC, ELAUNIN AND OXYTALAN FIBERS

The elastic system fibres of the female urethra were investigated in s even dogs of different breeds. The fibres were stained and differentia ted with orcein, Verhoeff's iron hematoxylin, and pararosanilin-based aldehyde fuchsin, with and without previous oxidation. Orcein and alde hyde fuchsin revealed some subepithelial longitudinally orientated del icate fibres (elaunin fibres) and numerous coarse longitudinal fibres (elastic fibres) in the deeper subepithelial connective tissue contain ing the vascular plexus, as well as a network of fibres of different c alibers in the periurethral connective tissue. Elastic system fibres w ere also found in association with the sinusoids of the vascular plexu s and the urethral smooth musculature. Verhoeff's iron hematoxylin onl y reacted distinctly with coarse (elastic) fibres. When applied follow ing oxidation, aldehyde fuchsin disclosed an extensive meshwork of add itional delicate fibres (oxytalan fibres) in the subepithelial connect ive tissue adjacent to the basement membrane. Oxytalan fibres were als o discernible in the sinusoidal adventitia of the vascular plexus, as well as between smooth and striated muscle fibres. Due to the predomin antly longitudinal orientation of the elastic system fibres and the lo w urethral resistance to manual expression of urine from the bladder p ost mortally, when the elasticity of the urethra is still intact and t he activity of other continence factors can be excluded, the elastic t issue is not judged to be a major contributory factor to urinary conti nence.