Liver - Microscopic Anatomy

General structure
The liver is covered (except for bare triangular area on the upper surface) from the visceral peritoneum, consisting of the mesothelium, a single layer of surface cells and underlying tissue extraperitoneal. It is also completely surrounded by loose connective tissue component of the capsule of Glisson, who is also the neurovascular bundle at the hilum. Out from it and trabecular connective tissue septa that penetrate the liver parenchyma, dividing it in the portal tracts. Within each area there is a branch of the portal vein, a hepatic artery, a bile duct (portal triad) and often also small lymphatic vessels and nerve branches.

The parenchyma is composed of plates instead of the complex three-dimensional structure and consist of a single layer of cells, or hepatocytes, the major liver and those that perform almost all of its metabolic functions. Each layer of hepatocytes is separated from each other by a venous sinusoid, resulting from the branching of the portal vein which runs in the portal space. It takes up space portal to centrilobular vein. Hepatocytes do not adhere to the venous sinusoids, but are separated by a small intercellular space dilation in pathological conditions (0.2-0.5 μm), said space of Disse.

In the space of Disse contains mainly fibers of collagen type I, III and IV and there protrude dell'epatocita the microvilli and the nerve endings. There is considerable scope for exchange between hepatocytes and sinusoidal veins or because of the greater absorption surface provided by the microvilli at the beginning, that the fenestrations present in the venous sinusoids. Among un'epatocita and the other (on each side of the cell) are those small showers bile canaliculi, so that each hepatocyte is almost surrounded it. The canaliculi drain into bile ducts of greater size, the canals of Hering, in turn these bile ducts of the portal triad, and these drain the bile ducts in the liver and then in the bile duct.

The ramifications of the hepatic artery are divided further into capillaries which then convey the blood into the venous sinusoids, or the same arterial branches converge in the sinusoids, so that the hepatocytes maintain a mixed blood of the arteries and veins. Centrilobular veins unite in the veins of higher caliber, the interlobular (placed between the liver lobules), which in turn drains into the hepatic veins and those in the inferior vena cava. One of the functional units of the liver, the largest in scale, is the liver lobule.

This is a pseudo-hexagonal-shaped structure (tends to be more regular in other animals not humans) whose skeleton is represented by plates of hepatocytes separated by sinusoids resulting from venous branch portal vein. The edges are not restricted to radially expand from a vein tax centrilobular hepatic veins, but have branched structures in three dimensions and difficult to schematization. Each lobule is surrounded by thin connective tissue septa, and every "corner" opens a portal triad. Smallest functional unit of the liver lobule is the liver acinus. A berry is a section of liver parenchyma oval shape, whose axis connects two centrilobular veins and less about one side of the hexagon formed by the liver lobule. Each berry is divisible by a functional point of view into three zones.

Zone 1 is defined periportal, and is the closest to the branching of the portal vein and the terminal branches of the feeding vessels, its major axis joining the two branches portals, the child is little depth in the parenchyma of the lobule. Zone 2, intermediate level, is a triangle that includes only the parenchyma of the lobule in its middle portion, zone 3, centrilobular, centrilobular vein is approaching and it includes a commission. The berries thus assumes an oval or diamond shape.

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