What is the function of liver zones?

What is the function of liver zones?

Zones differ by function: zone I hepatocytes are specialized for oxidative liver functions such as gluconeogenesis, β-oxidation of fatty acids and cholesterol synthesis. zone III cells are more important for glycolysis, lipogenesis and cytochrome P-450-based drug detoxification.

What are acinar zones?

The acinus is a unit that contains a small portal tract at the center and terminal hepatic venules at the periphery. It is the smallest functional unit and is divided into zones 1, 2, and 3, wherein zone 1 surrounds the portal tract and zone 3 surrounds the hepatic venule.

What does the portal triad do?

Portal triads are composed of three major tubes. Branches of the hepatic artery carry oxygenated blood to the hepatocytes, while branches of the portal vein carry blood with nutrients from the small intestine. The bile duct carries bile products away from the hepatocytes, to the larger ducts and gall bladder.

What is metabolic zonation?

According to the concept of metabolic zonation, the spatial organization of the various metabolic pathways and functions forms the basis for the efficient adaptation of liver metabolism to the different nutritional requirements of the whole organism in different metabolic states.

Why does alcoholic hepatitis affect Zone 3?

Alcoholic steatosis is mostly macrovesicular and more prominent in zone three of the liver acinus, which is the region surrounding the central veins. Pathophysiology of ALD has not been completely clarified yet. Ethanol metabolism alters the intra-mitochondrial redox potential via the generation of NADH by ADH.

What zone of the liver does alcohol affect?

Acetaldehyde is increased in zone 3 (also the maximal site of action of alcohol dehydrogenase). This is also the site of the terminal veins making this zone the most hypoxic and therefore highly susceptible to hypoxic injury. Oxygen derived free radicals may cause direct hepatocyte injury by lipid peroxidation.

How many zones are in the liver?

Three zones can be distinguished. 1, the periportal zone; 2, the intermediary zone; 3, the perivenous, pericentral, or centrilobular zone. (B) Liver sinusoid and oxygen gradient. Hepatocytes (HC), are connected with each other, bile canaliculi (BC) transport the bile formed in HC into the bile duct (BD).

What is a lobule liver?

The hepatic lobule is the anatomic unit of the liver. In the anatomic model, liver lobules are organized into irregular polygons demarcated by connective tissue and composed of plates of hepatocytes radiating outward from the central vein to the portal triads (Figure 61-1).

What are three important functions of the liver?

Functions of the liver

• Production of bile, which helps carry away waste and break down fats in the small intestine during digestion.
• Production of certain proteins for blood plasma.
• Production of cholesterol and special proteins to help carry fats through the body.

What drains blood from the liver?

The blood drains out of the liver via the hepatic vein. The liver tissue is not vascularised with a capillary network as with most other organs, but consists of blood filled sinusoids surrounding the hepatic cells.

What zone of the liver is found around the central vein where the oxygen level of the blood is very poor?

At the periphery of the lobule are portal triads. Functionally, the liver can be divided into three zones, based upon oxygen supply. Zone 1 encircles the portal tracts where the oxygenated blood from hepatic arteries enters. Zone 3 is located around central veins, where oxygenation is poor.

What is hepatic Zonated metabolism?

The segregation of hepatocytes into discrete functional areas is referred to as ‘Liver Zonation’ and is the basis for the partition of the hepatic lobule into three metabolic zones: periportal Zone 1 consisting of 6–8 hepatocyte layers that receive blood enriched in oxygen and nutrients and control glycogen metabolism.

What are the zones of the liver?

Functionally, the liver can be divided into three zones, based upon oxygensupply. Zone 1 encircles the portal tracts where the oxygenated bloodfrom hepatic arteries enters. Zone 3 is located around central veins,where oxygenation is poor. Zone 2 is located in between.

What is the difference between Zone 1 and Zone 3 hepatocytes?

Zones differ by function: zone I hepatocytes are specialized for oxidative liver functions such as gluconeogenesis, β-oxidation of fatty acids and cholesterol synthesis zone III cells are more important for glycolysis, lipogenesis and cytochrome P-450-based drug detoxification.

What are the zonal injury patterns of liver fibrosis?

Other zonal injury patterns include zone I deposition of hemosiderin in hemochromatosis and zone II necrosis in yellow fever. Bridging fibrosis, a type of fibrosis seen in several types of liver injury, describes fibrosis from the central vein to the portal triad.

What are the portal triads of the liver?

At the periphery of the lobule are portal triads. Functionally, the liver can be divided into three zones, based upon oxygensupply. Zone 1 encircles the portal tracts where the oxygenated bloodfrom hepatic arteries enters. Zone 3 is located around central veins,where oxygenation is poor.