At the periphery of the lobule, portal canals can be seen (P in HA6, and the central portion of images HA8). The portal canals contain bile ducts lined with simple cuboidal epithelium (B), an arteriolar branch of the hepatic artery (A), and a tributary of the portal vein (P). These three structures comprise the "portal triad", but the portal canals also contain small lymphatic vessels (L in HA8) as well as autonomic nerves (invisible in this image due to magnification).