[TA] surgically resectable portions of the liver supplied by independent branches of the portal vein and hepatic artery, and drained by independent lobular branches of the hepatic bile ducts; thus, the naming and numbering of the eight hepatic segments in TA is based on the portobilioarterial distribution: posterior [I], lateral [II], left lateral anterior [III], and medial [IV] segments of the left (part of) liver, and anterior medial [V], right anterior lateral [VI], posterior lateral [VII], and posterior medial [VIII] segments of the right (part of) liver; the hepatic segments are separated by the vertical planes (portal fissures) of the three major (right, intermediate, and left) hepatic veins; those of the right (part of) liver are also separated by the horizontal plane of the right division of the portobilioarterial tree.anterior segment, lateral segment, medial segment, posterior segment SYN: segmenta hepatis [TA], segments of liver.