The hepatic lobule can be described in terms of metabolic "zones", describing the hepatic
acinus (terminal acinus). Each zone is centered on the line connecting two
portal triads and extends outwards to the two adjacent central veins. The periportal zone I is nearest to the entering vascular supply and receives the most oxygenated blood, making it least sensitive to
ischemic injury while making it very susceptible to viral hepatitis. Conversely, the centrilobular zone III has the poorest oxygenation, and will be most affected during a time of
ischemia.
Portal triad A
portal triad (also known as
portal canal,
portal field,
portal area, or
portal tract) is a distinctive arrangement within lobules. It consists of the following five structures: •
proper hepatic artery, an arteriole branch of the hepatic artery that supplies oxygen •
hepatic portal vein, a venule branch of the portal vein, with blood rich in nutrients but low in oxygen • one or two small
bile ductules of cuboidal epithelium, branches of the
bile conducting system. •
lymphatic vessels • branch of the
vagus nerve The misnomer "portal triad" traditionally has included only the first three structures, and was named before lymphatic vessels were discovered in the structure. It can refer both to the largest branch of each of these vessels running inside the
hepatoduodenal ligament, and to the smaller branches of these vessels inside the liver. In the smaller portal triads, the four vessels lie in a network of
connective tissue and are surrounded on all sides by
hepatocytes. The ring of hepatocytes abutting the connective tissue of the triad is called the
periportal limiting plate. File:Portal triad.JPG|Portal triad File:Gray1093.png|Labeled sketch of a portal canal File:Leber Glisson (Ratte).jpg|Portal triad of a rat liver,
1 branch of hepatic artery,
2 branch of portal vein,
3 bile duct File:Liver portal triad.png|Portal triad of mouse liver. 1= bile duct, 2= branch of hepatic artery, 3= branch of portal vein, 4= lymphatic vessels
Periportal space The
periportal space (), or
periportal space of Mall, is a space between the stroma of the
portal canal and the outermost
hepatocytes in the hepatic lobule, and is thought to be one of the sites where
lymph originates in the liver. Fluid (residual blood plasma) that is not taken up by hepatocytes drains into the periportal space, and is taken up by the lymphatic vessels that accompany the other
portal triad constituents. ==Function==