Posted June 25, 2017. Pathology - Liver
There are three compartments:
Intervening parenchyma or lobule.
The liver is an exocrine organ and it has metabolic functions.
Kiernan in 1833 introduces the concept of lobule which measures 0.5 to 2 mm in diameter with 4 to 5 portal spaces.
Rapaport et al in 1945 introduced the concept of the functional unit which is called acinus or metabolic lobule. This concept depends on oxygen supply and nutrients.
Zone I: This zone has the best blood supply and prone to most toxic injuries. if an injury occurs in this zone, well be the first to regenerates. In this zone glycogen synthesis, glycogenolysis, protein, and formation of plasma protein take place.
Zone II: in this zone, there is reasonable blood supply, it shares function with zone I and zone III
Zone III: This zone has the poorest blood supply and prone to more hypoxic injury. In this zone, there is glycogen storage, lipid, pigment formation and metabolism of drugs and chemicals.
In the liver 80 % are hepatocytes. In 70 kg man, there are roughly 250 billion hepatocytes.
Zone I is around the hepatic artery and portal vein while zone III is around the central vein where there is poor blood supply.
Limiting plate is the hepatocytes which line up the portal Triad.
Fawcett in 1955 described that 60 % of the liver cells are polygonal 20 to 30 um in diameter. Lifespan in ( experimental animals ) is 150 days. If 80 to 90 % of the liver is resected rest of the liver regenerates to full size.
Each hepatocyte is six-sided structure, in between, there is a sinusoid lined by endothelial cells. In between there are cells derived from monocytes, they can clear micro-organism and cancer cells.
The bile duct is between the wall of two adjacent hepatocytes. This is basically a groove which continues with other grooves. In between the hepatocytes and sinusoid, there is a space called space of Disse. this is 300 to 400 nm wide. In this space, there is tissue fluid and lymph flows outwards. In this space, there are lipocytes these are called Ito cells. These lipocytes store fat and vitamin A.
In between the hepatocytes and sinusoid, there is a space called space of Disse. this is 300 to 400 nm wide. In this space, there is tissue fluid and lymph flows outwards. In this space, there are lipocytes these are called Ito cells. These lipocytes store fat and vitamin A.
This is an energy providing unit through the citric acid cycle. In this unit oxidative phosphorylation, beta-oxidation of fatty acid and heme synthesis takes place.
Rough Endoplasmic Reticulum.
There is a synthesis of albumin, triglyceride, lipoprotein, G-6-PD, Glycogenosis, specific protein for blood coagulation and enzymes take place.
Smooth Endoplasmic Reticulum
There is bilirubin conjugation, detoxification, synthesis of steroids and Cholesterol and bile acid place. The synthesis ability is increased by phenobarbitone.There is an accumulation of glycogen and metabolism of drugs.
It is the packing site for lipoprotein and glycoproteins. It is filled with LDL.
It contains various hydrolytic enzymes. It stores ferritin, lipofuscin, and bile pigments, and copper. Because of the presence of enzymes, there is disposition and catabolism of endogenous and exogenous substances.
These cells belong to the reticuloendothelial system. The Kupffer's cells are the largest cells of the mononuclear phagocytic system.They can endocytose bacteria, endotoxins, effete cells and has a role in iron metabolism. These cells have a receptor for Fc portion of IgG, C3b, receptor for insulin and glycogen.
These cells have Fc receptor. Determine the exchange of fluid and particulates from space of Disse and hepatocytes.
Lipocytes are also called as Ito cells and they store vitamin A and other fat-soluble vitamins. Lipocytes takes an active role in fibrogenesis and may lead to cirrhosis.
These are lying in the space of Disse. These may play an active role in portal hypertension.
This ultrastructure of the liver cell can be elaborated better by the following diagram.
Plasma membrane and the membrane Traffic
The plasma membrane is rich in the receptors. This is the specific site for hormones and metabolites. Most molecules enter hepatocytes through these receptors.
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The liver develops In the third week of gestation from foregut (primitive duodenum) which develops from endodermal cells. Also, gallbladder and hepatocytes develop from the endodermal cells.
Connective tissue and sinusoids develop from mesenchymal cells.
Intrahepatic bile duct development complete at a 3rd month and bile secretion also start by that time.
The liver is the main organ to store iron and is the site for hematopoiesis. Hematopoiesis stops in two months after birth but may be found in occasional foci in the liver. In premature baby these foci are abundant. The weight of the liver in full term baby is 75 to 180g.Umbilical Vein is the main source of blood supply in fetus after delivery it atrophies and gets round ligament. Liver grows slower than other structures in adult liver weighs 1200 to1500 g (1350G)⅕ of the total body weight (2.5% of total body weight)
The weight of the liver in full term baby is 75 to 180 g. Umbilical Vein is the main source of blood supply in fetus after delivery it atrophies and gets round ligament. Liver grows slower than other structures in adult liver weighs 1200 to1500 g (1350G)⅕ of the total body weight (2.5% of total body weight)
Umbilical Vein is the main source of blood supply in fetus after delivery, it atrophies and transforms into round ligament. Liver grows slower than other structures in adult liver weighs 1200 to1500 g (1350G)⅕ of the total body weight (2.5% of total body weight)
The Liver grows slower than other structures. in adult liver weighs 1200 to1500 g (average 1350G) and is 1/5 Th of the total body weight (2.5% of total body weight).
The liver is divided by a falciform ligament into right and left lobes.The right lobe is divided into quadrate lobe (inferior surface) and caudate lobe ( posterior surface).The upper border extends to the 5th intercostal space.
The liver is covered by thin fibrous capsule called Glisson capsule.The gallbladder is under the right lobe. The Porta hepatis is a deep fissure in the inferior surface of the liver through which all the neurovascular structures( except hepatic veins ) and hepatic ducts enter or leave the liver.It contains the right and left hepatic ducts, right and left branches of the hepatic artery and portal vein. The left lobe is six times smaller than the right lobe.
In the porta hepatis, the hepatic artery is anterior, bile duct also anterior and the portal vein is posterior.
Teres ligament developed from an inferior umbilical vein. Ligamentum venosum developed from posterior ductus venosus. The lower edge of the liver is unusual to be 1 to 3 cm below the costal margin.
The connective tissue surrounds all blood vessels and ducts to finest radicals to join inner aspect of Glisson capsule.
Hepatic artery carries 600 ml of blood per minute while portal vein 900 ml of blood per minutes. Hepatic artery supplies 30 to 40 % of oxygen while portal vein supplies 50 to 60% oxygen. The pressure in the hepatic artery is 90 mm of Hg and in the portal vein is 8 to 10 mm of Hg.
The portal vein has a high level of oxygen content equal to 80% saturation. Mixing of the portal vein and hepatic artery blood leads to drop in the arterial pressure.
These vessels enter into sinusoids and all sinusoids drain blood to central veins. All central veins give rise to right and left hepatic veins Which continue to inferior vena cava.
From the liver left and right duct joins to form the common hepatic duct.The common hepatic duct is joined by the cystic duct from the gallbladder.They give rise to common bile duct the diameter of the duct is .5 to 1.5cm.The common bile duct is joined by the pancreatic duct and they open to the ampulla of water in the duodenum, the ampulla of water is controlled by sphincter of Oddi which is Spiral valve, is a fold of mucosa.