Histology Slides Database

Saturday, October 8, 2011

The ultrastructure of hepatocytes

The ultrastructure of hepatocytes differs In the three zones. As gluconeogenesis occurs primarily in zone I; so SER is sparse, mitochondria are elongated and glycogen is more abundant.

As glycolysis and lipid metabolism is frequent in zone III, so SER is well developed here and the mitochondria are numerous and quite small. The glycogen is sparse.

The hepatocytes of zone II show intermediate features.

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Histology Of Liver or Hepatic Acinus

Liver or Hepatic Acinus: It is the most preferred structural and functional unit of the liver now days. In cross section, it is a diamond-shaped or elliptical subdivision of liver parenchyma. It comprises parts of two adjacent hepatic lobules; the narrower ends of diamond are formed by two central veins, while the central wider part is formed by two portal triads (vascular core). The hepatic acinus is commonly divided into three zones (table 10.12).

Zone I is formed by the central part of liver acinus, which is present at the junction of adjacent sides, or peripheral parts of two hexagonal hepatic lobules. It receives best of the nutritive and oxygenated blood (through hepatic artery and portal vein), so hepatocytes of zone I are more liable to metabolic changes (like storage and depletion of glycogen). Similarly it is more liable to damage by toxins (eclampsia), phosphorous poisoning, chronic hepatitis and primary biliary cirrhosis.

Zone II is intermediate in position and less affected by the conditions producing changes in zones I and ill. However, it undergoes necrosis in yellow fever.

The peripheral zone (zone III) (hepatocytes of a liver acinus present nearer to central veins) receives less oxygenated and nutritive blood, so more liable to damage by hypoxia. It also undergoes necrosis in drug and chemical toxicity and right-sided cardiac failure.

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Histology of Portal Lobule and Hepatic Lobule

Portal Area/trlad/canal: It is present at the periphery of hepatic lobule. Each portal area comprises of branches of portal vein, hepatic artery, bile duct and lymphatic vessels lying in small amount of connective tissue. Around the periphery of hepatic lobules can be seen several portal canals within the interlobular septa.

Hepatic lobule is the structural unit of liver while the functional unit is portal lobule. The recent studies have suggested another functional unit of liver, the hepatic acinus.

Portal Lobule: Portal area or portal canaJ is present at the center of portal lobule. Portal lobule consists of liver tissue draining bile into the bile duct of that portal area. Such a unit is triangular in cross section, containing part of three adjacent classic hepatic lobules and has central vein at each of three corners. This represents the area of drainage for radical of a bile duct present in the portal canal.

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Histology Of The duct system for the biliary passage

Histology Of The duct system for the biliary passage: The sides of hepatocytes related to sinusoids are referred to as sinusoidal domains while the sides related to other hepatocytes are referred to as lateral domains. The bile secreted by hepatocytes passes initially into bile canaliculi (0.5-1.5 |im), which are the intercellular canals (midway of lateral domains). So these bile canaliculi are simple spaces between adjoining liver cells and have no other lining epithelium. These canals anastomose with each other and pass to the periphery of hepatic lobules where these empty into short canals known as canals of Herlng Preductules/Cholangloles: The cholangioles are lined by simple cubical epithelium and drain in to bile ductules, which drain into bile ducts.

The bile ductules and bile ducts are lined by simple cubical epithelium. The intrahepatic ducts (lined by simple columnar epithelium) by the union of bile ducts, the intrahepatic ducts lead to extrahepatic ducts which are lined by simple columnar epithelial surrounded by C.T. and smooth muscles. These unite to form the common bile duct, which is also lined by simple columnar epithelium surrounded by C.T. and smooth muscle cells. The C.T. contains tubule-alveolar mucous glands.

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Detailed histology Of HEPATOCYTES

Detailed histology Of HEPATOCYTES

The hepatocytes are polyhedral (5-12 sides) in shape (80% of cell population) with mostly single rounded nucleus. 25% of hepatocytes are binucleated. Each nucleus contains prominent nucleolus.

The plasma membrane of hepatocytes bear microvilli more numerous towards sinusoids than towards bile canaliculus). The cytoplasm of hepatocytes is acidophilic due to richness in smooth endoplasmic reticulum and glycogen but contains basophilic bodies as well due to RER.

The hepatocytes are arranged in radiating plates of one to two cell thicknesses around the central vein. These cords or plates of hepatocytes branch and anastomose with other cords and in this way form a three dimensional framework of liver parenchyma.

The hepatic plates are separated from each other by blood sinusoids and by perisinusoidal tissue spaces (spaces of Dlsse). The sinusoids are lined by two types of cells; the simple squamous endothelial cells (non-continuous epithelium) and von Kupffer cells (stellate shaped phagocytic cells of reticuloendothelial system or mononuclear phagocytic or macrophage system). The plasma escaping from sinusoids passes out into the perisinusoidal space, which surrounds the sinusoids.

So perisinusoidal space is present between the hepatic sinusoids and hepatocytes. This space contains reticular fibres, stellate-shaped adipocytes (lipocytes or Ito cells), plasma (tissue fluid) and microvilli of hepatocytes. Ito cells are typical stellate shaped cells. Space of Disse continues into space of MalL, which contains structures of portal triad. The lymphatic vessels also begin in the spaces of Mall along with other structures of portal triad. The liver produces 50% of the lymph found in the thoracic duct.

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Wednesday, September 21, 2011

eyelid diagram histology slides database

Click on the photo to enlarge and view the eyelid diagram histology slides database
Use the search feature given at the top of this page to find more histology slides photos and histology diagrams !
Eye lid comprises of skin, a muscular layer , hairs and many glands, The secretions of these glands lubricate the eyes and also Protect them as seen in the diagram the eyelids comprise of glands , eye lashes, muscle layer in a stroma !

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jejunum diagram at histology slides database

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jejunum diagram at histology slides database
The histology of jejunum is very much similar to the histology of duodenum and ileum but there are many major differences too. The difference is basically in the epithelium and the glands types. Jejunum is the second part of small intestine and it lies between duodenum and ileum .
The histology of jejunum is explained well in the diagram uploaded above. Click on the diagram above to enlarge it.

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