The aim of the present work was to study the normal microscopic arterial morphology of the descending colon and rectum in the dog. For this study, we used the organs of five dogs (Canis familiaris), which were injected with Mercox® through the caudal mesenteric artery, and studied by scanning electron microscopy. The branches of the long and short straight arteries and the anastomoses that join them, form four intraparietal plexuses which progressively, from the outwards inwards, were designated as: subserosal, muscular, submucosal and mucosal. The subserosal plexus is formed by an irregular rectangular shaped network, with its greater diameter being transversal. The muscular plexus is situated between the submucosal and subserosal plexuses. The plexus of the external muscular layer emits interfascicular longitudinal arterioles that form numerous anastomoses with one another, from which, in turn, the fascicular arterioles emerge. The internal muscular plexus emits interfascicular transverse arterioles, perpendicular to the greatest axis of the colon, forming numerous anastomoses with one another, from which the fascicular arterioles emerge. The submucosal plexus is situated between the internal muscular and mucosal plexuses. The centrifugal arterioles emerge from these to the muscular layers as well as the centripetal arterioles, the deep submucosal or mucosal arterioles, which are directed to the mucosa, forming the corresponding plexus. The mucosal plexus is formed by pre‑capillary arterioles, situated at the base of the mucosa near the muscular mucosa, by interglandular capillaries throughout its thickness and by periorificial or periglandular capillaries. Each intraparietal plexus of the colon has an abundant vascular architecture with numerous anastomoses. It may be concluded that the irrigation of the organ, from an anatomical point of view, is of the anastomotic type.