Review the structural organization of the liver (hepatic) lobule, noting inflow of blood to lobules from branches of both the hepatic artery and hepatic portal vein and outflow through central venules to branches of the hepatic vein. Bile originates within lobules and is drained via branches of the bile duct located in the portal areas. A simplified version of the classic liver lobule in transverse section is shown in the diagram to the right. Click here for a larger view.

• The liver histology is complex, but this narrated overview of the liver will help explain things. Try it.
• Examine these sections of liver (sample 1, sample 2, sample 3). With low magnification, locate a set of portal areas (triads) outlining a lobule.
• With higher power, identify the central venule in the center of the lobule and the triad of components in the portal area, namely branches of the hepatic portal vein (PV), hepatic artery (HA), and bile ductules (BD). The portal areas also contain lymphatic vessels (LV) with their typical thin endothelium and irregularly shaped lumens. Use the image at the right to help you locate these structures.

Clinical note: Hepatitis involves infection or inflammation of hepatocytes and other epithelial components in the liver. Cirrhosis involves excessive proliferation of fibroblasts and collagen deposition in the stroma of the liver. Hepatocytes have a remarkable capacity for regeneration, but chronic, long-term alcoholism leads to the death of these cells and cirrhosis. Jaundice, due to failure of the hepatocytes to conjugate bilirubin, is characterized by accumulation of bilirubin in the skin and sclera of the eyes. Jaundice is common in patients with liver disease.

Detail of the hepatic lobule.