A quantitative description of the epididymis and its microvasculature: an age-related study in the rat.

The morphology of the epididymal duct and, in particular, the epididymal microvasculature was examined at the light microscope level in young sexually-mature rats (3-5 months) and aged rats (18 months) to investigate the structural changes that may occur within the organ as a result of ageing, and which may predispose the organ to pathological changes. Quantitative data on the microvascular network of the epididymis (percentage of capillaries in the interstitial region, average area and surface density of the capillary lumen) were collected in 4 regions of the epididymis: the initial segment, caput, corpus and cauda. Epithelial cell height, epididymal lumen diameter, number of smooth muscle cells and percentage of smooth muscle surrounding the duct were also assessed within the same 4 regions. The data for both young and aged groups revealed a trend of decreasing capillary size from the initial segment of the epididymis to the cauda by 23%. Further, the percentage of capillaries within the interstitial region of the epididymis decreases dramatically (52%) in the same direction. The possible contribution of lymphatic capillaries to the data is discussed. The data revealed that none of the parameters assessed changed significantly up to 18 months of age. The quantitative data on the microvascular morphology of the epididymis presented in this study provide the basis for subsequent studies directed at the blood flow dynamics of the organ.