Biological Chemistry - Berezov T. T., Korovkin B. F. 1998

Liver

The paramount importance of the Liver in METABOLISM is primarily determined by its role as a major metabolic crossroads between the portal and systemic circulations. In humans, over 70% of the Blood supply reaches the liver via the portal vein, while the remaining blood is delivered through the hepatic artery. Portal venous blood drains the absorptive surface of the intestines; consequently, the vast majority of substances absorbed from the gut pass through the liver first (with the exception of Lipids, which are transported primarily via The Lymphatic system).

Thus, the liver Functions as the primary regulator of blood levels for nutrients derived from food. This principle is well illustrated by a fundamental physiological fact: although the absorption of nutrients from the intestine into the bloodstream is intermittent and variable—causing fluctuations in the concentration of various compounds (such as glucose and Amino Acids) within the portal Circulation—their concentrations in the systemic circulation remain remarkably stable. All of this underscores the critical role of the liver in maintaining systemic Homeostasis. In addition, the liver performs a vital excretory function that is intimately linked to its detoxification duties.

Overall, it is no exaggeration to state that there is no metabolic pathway in the body that is not directly or indirectly regulated by the liver. For this reason, many of the liver's most crucial functions have already been discussed in the relevant chapters of this textbook. This chapter aims to provide a comprehensive Overview of the liver's overarching role in the metabolism of the whole Organism.