The Adamkiewicz artery originates from the lower intercostal/lumbar artery, runs along the vertebral roots of the spinal nerve, and communicates with the anterior spinal artery. In graft replacement for an aortic aneurysm, the lower intercostal/lumbar artery should be reconstructed to maintain the arterial blood supply to the lumbar spinal cord via the Adamkiewicz artery. To date, there are few reports on the histological characteristics of the arterial pathway from the aorta to the anterior spinal artery via the Adamkiewicz artery as well as the pathway in the Adamkiewicz artery. In addition, there is a possibility that this arterial pathway was degenerated by the aortic aneurysm. In this study, we attempted to reveal the histological characteristics of the arterial pathway by using elderly cadavers with or without unruptured aortic aneurysm. Specimens were obtained from 190 elderly cadavers (fixed in 10% formalin). These cadavers included 16 cases of aortic aneurysms. We collected fragments of the intercostal/lumbar artery, its dorsal branch, the Adamkiewicz artery, and the anterior spinal artery. After routine histological procedures, several staining procedures were performed for each section. A morphometric study was conducted at the light-microscopic level. The Adamkiewicz artery is composed of a thick intima that contains multiple thick elastic fiber layers and, probably, numerous intimal smooth muscle cells. Among the cadavers, the intimal thickness varied significantly in the intercostal/lumbar artery and the Adamkiewicz artery; it tended to be constant, irrespective of luminar dilatation in the Adamkiewicz artery, in contrast to other arteries. No significant difference was observed between the specimens with or without unruptured aortic aneurysms in all the parameters that were measured. The Adamkiewicz artery appeared to be capable of adapting to acute and chronic changes in systemic status that develop with aging because of its thick intima that contained numerous smooth muscles and elastic fibers. Against various events of systemic circulatory dysfunctions such as hypertension, its unique morphology suggested that this artery may play the critical role of a modulator, or even a barrier, that is intercalated along the arterial route to the lumbar cord.