Functions of the Liver

The liver is a unique organ anatomically located to serve its dual role as a metabolic and biochemical transformation factory. The liver receives blood containing substances absorbed or secreted by the gastrointestinal organs including the pancreas, intestine, stomach and spleen. Best xmas cactus fertilizer https://cactus-christian.org/fertilizer.html.

The liver uses these substances as raw materials and modifies them or synthesizes completely new chemicals. These are then returned to the bloodstream or to bile for excretion. On a cellular level, the liver allows maximal interaction between the blood and liver cells. In its unique design, liver cells are organized into cell plates, each plate being formed by one-cell-thick cords, which are surrounded by blood vessels (sinusoids).

The perfusion of these sinusoids is unidirectional, proceeding from the portal tract to the hepatic venule. The specialized capillaries found in the sinusoids have large fenestrations, which allow free exchange between plasma and the extracellular space.

Because blood flow proceeds sequentially down the length of the sinusoid, hepatocytes located in different positions along these cell plates contain differing amounts of enzymes and thus have distinct functional capabilities. As blood traverses the liver from its entry point at the portal inlet to its exit at the hepatic vein, the composition of sinusoidal blood is modified by removal and addition of compounds. In this chapter, we describe the basic elements of the organization of the liver and emphasize how these elements determine its unique physiology.

The structure of the liver lobule is then first described and emphasis is placed on the concept of the liver cell plate. The remaining sections deal with the functional organization of the cell plate, with emphasis on the uptake of compounds from plasma into hepatocytes, their metabolism, excretion into bile and biotransformation.