The Distribution and Structure of the Microvasculature of the Phallus in the Ostrich (Struthio camelus)

This study determined the distribution and specialized morphology (gaps and fenestrations, irregular endothelium, internalization of luminal material) of vessels in the spongy and erectile tissue of the phallus in the ostrich. Specimens from the phallus harvested from 18 sexual mature and active ostriches were utilized. General routine fixation was used for tissue blocks and then they were processed conventionally for observation under the Transmission Electron Microscope (TEM). The spongy tissue in the root of the phallus exhibited several blood vessels (mainly venules) within connective tissue strands. The capillaries displayed thick and attenuated endothelial profiles, whereas the venules were lined with an attenuated endothelium. Both vessel types displayed fenestrations and prominent gaps supported by a continuation of the basal lamina. Numerous cytoplasmic processes extended from the capillary endothelium, in places appearing to enclose and sequestrate luminal contents by phagocytosis. The internalized material appeared in the form of relatively large, pale vesicles. The endothelium was extremely irregular in profile, in some instances appearing to be composed of more than one layer of squamous cells. The erectile tissue lining the phallic sulcus presented relatively few capillaries and venules. These vessels exhibited features similar to those seen in the spongy tissue but the endothelial cells were markedly more complex and irregular in design.