On the Sensory Nerve Supply of the Urethra and the Penis in Dog

Abstract

The sensory nerve supply of the urethra of dog is very notable in general, and in particular, most liberal in the pars prostatica but somewhat less so in the partes praeprostatica, membranacea and cavernosa.The sensory fibres entering the mucous membrane of the pars praeprostatica end in subepithelial and intraepithelial simple branched terminations in most cases but more rarely in capsulated and uncapsulted small-sized glomerular bodies. The uncapsulated bodies are smaller than the capsulated. Many terminal fibres in the branched terminations show change in size and end searply or bluntly. Small endbodies resembling PACINIan bodies are not rarely found in the submucosa here.In the pars prostatica, simple branched termiations are often found along the ducts of the prostatic glands. Their terminal fibres often enter the epithelium. Very small-sized PACINIan bodies are found in the submucosa in this part. Most of the sensory fibres running into the mucous membrane here mostly end in branched and less often in corpuscular terminations. These are superior in number as well as in construction to those in the preprostatic part. The end bodies here too mostly resemble the genital nerve bodies Type I, but a fow belong to the Type II of such bodies. Most of the branched terminations are formed intraepithelially and not rarely complexly enough. Their terminal fibres, sometimes rather thick in size, often show conspicuous change in size.In the pars membranacea urethrae, PACINIan bodies are found in the adventitia covering the m. urethralis and these are often found in groups of 2 or 3 bodies each. The connective tissue lamellae count from 10 to 15 and the incoming single thick sensory fibre ends in a blunt point withouf branching. Very peculiar branched terminations formed by enormously thick sensory fibres as found in the urethra of cat are found in the inner circular smooth muscle layer of the m. urethralis of dog, too. These are well developed in the proximal portion of the part where the muscle layer is in good development but even in the more distal portions where the muscle layer is poorer, similar terminations are not at all absent. These seem to belong to the category of the ABE's so-called prostatic sensory terminations found in the same part in man.In the pars membranacea, the glomerular and branched terminations formed in the mucous membrane are less well developed, eithar numerically or structurally. Neither PACINIan body nor end bulb have been found here. The glomerular terminations comprise capsulted and uncapsulated ones and lose both in number and in size in the more distal portions. These glomerular terminations are found not rarely in the venous plexus outside the mucous membrane, too.The branched terminations also grow slowly poorer distalwards, but often I found rather complex branched terminations unexpectedly in the distalmost area. The terminal fibres of these terminations are often thick and show conspicuous change in size and mostly end in the epithelium, but subepithelial branched terminations are not rare either. The terminal fibres showing change in size of the latter very frequently run up into the epithelium, then curve down again into the epithelial basis and end sharply. Branched terminations of other types, i. e., those with branch fibres spreading arborescently toward the epithelium and those of a few branch fibres showing change in size during their winding courses spread out over a wide area in the propria, are found only very scantily.The sensory supply of the pars cavernosa urethrae of dog is poorer than in man but is far better than in cat. Here, branched terminations are formed, most often intraepithelially, while the glomerular terminations are far larger in number and better in formation than those in the pars membranacea; intraepithelial fibres are often sent out from the latter