Histomorphologic study of the renal artery in post-natal life of sheep (Ovis aries)

The purpose of this study was to gain more information on the structure of different layers of renal arteryand comparing these structures in post-natal male and female sheep. To do so, right and left renal arteries of6 adult and 6 newborn animals were dissected; the middle parts of arteries were only collected. After tissueprocessing using paraffin embedding method, 5–6-μm sections were cut and stained with haematoxylin andeosin, green Masson’s trichrome and Verhoeff’s elastic fiber methods. Three layers were identified in thewall of artery in both sexes. In tunica media the number of rows of circular smooth muscle cells was 15–25rows in newborn and 30–40 in adult sheep. External elastic membrane was visible in adult and wasstructurally thinner than the internal membrane. Tunica adventitia was visible in all samples and collagenfibers and smooth muscles bundle were distinguished. The existence of these muscle bundles in externallayer of renal artery was not reported previously in domestic animals and regarded as a new finding in thepresent study. These muscle bundles were thicker in adult than in newborn animals and probably have arelationship with the function of kidney’s vascular system. It was concluded that these bundles maypotentiate the tunica media muscle cells to prevent hypertension crisis