The vasculature of the male reproductive organs of the ostrich (Struthio Camelus)

Abstract

The ostrich industry is a small, important section of the economy in the Republic of South Africa. The demand for ostrich products is high in the world, but the ostrich industry faces some production problems, one of which is the low fertility of commercially farmed ostriches. This study aimed to determine the vasculature of the reproductive system in the male ostrich and determine the kind of blood-testis and blood-epididymis barriers, since there is no published information regarding this aspect. Thus 85 pre-pubertal and adult sexually active male ostrich were studied. Arterial supply, venous drainage, microvasculature of the male reproductive system, and blood-testis and blood-epididymal barriers, were determined in this specie, for the first time. Results show that the pattern of the arterial blood supply to the reproductive organs of the male ostrich is similar to that of the domestic fowl and pigeon. However, few highlighted, distinctive, features were noted, the communication between the cranial renal arteries and middle renal arteries via collateral circulation. The pattern of the venous drainage of the reproductive organs of the male ostrich, was similar to that described in the domestic fowl. However, important differences were the fusion between the caudal renal veins and the existence of a unique caudal median vein that had the caudal mesenteric vein as tributary. The epithelial structure in the proximal efferent ducts was consistent with fluid absorption. The fluid absorbed in the efferent ducts is harvested also by capillary lymphatics situated in the interstitium. Both the cranial and caudal segments of Ductus deferens and the Receptaculum ductus deferentis displayed one vascular networks beneath the tubular epithelium and other capillaries, venules, arterioles and collecting veins were in the periphery. Arterioles and collecting veins were also under the serosa. Subepithelial capillaries, in those segments, lacked fenestrations. The spongy structure, in the root of phallus, exhibited several blood vessels in the strands. The capillaries and the venules displayed fenestrations. The erectile tissue in the phallic sulcus had the same features like the spongy in phallus. The spongy is comparable to corpus paracloacal vascular body present in other avian species and it should be called lymphobulbus phalli, it is the main source of lymph for phallus erection in the male ostrich. There are similarities in the microvasculature pattern between ostrich and domestic fowl, but there are some differences in the ostrich: (i) Absence of fenestrations in the capillaries of testis, (ii) Very simple and random distribution of stromal blood capillaries, arterioles and venules in the epididymis, Endothelial fenestrations, only in the blood capillaries close to proximal efferent ducts, (iv) Isolated lymphatic capillaries in the epididymis, occasionally, presented endothelial fenestrations fitted with a membranous diaphragm, (v) Existence of three vascular networks surrounding the tubule of deferent duct and receptaculum, that were determined on the base of the distribution, location and size of the vessels. The blood-testis barrier of the ostrich is positioned: in (i) the capillary endothelium in the interstitium, between adjacent seminiferous tubule, (ii) the boundary tissue, and (iii) between spermatogonia and spermatocytes, and spermatogonia and Sertoli cells, and finally, (iv) between Sertoli cells. The occluding junctional complexes between the various tissue or cellular elements are mainly tight junctions. The blood-epididymal barrier in the ostrich is revealed by participation of the endothelium of the capillaries and venules in the epididymal region, as lanthanum is trapped there, it does not appear beyond that point. The blood-testis and blood-epididymal barriers are similar to those described for the domestic rooster.