Location and structure of the liver – the liver is a large glandular organ weighing 1.2-1.5 kg, located under the right side of the diaphragm.
The liverhas a lobular structure; in terms of blood supply, the lobes are divided into segments.
The liverhistology shows islands of liver cells together with sinusoids. These sinusoids are in direct contact with the liver cells and allow substances to be exchanged between the blood and the liver cells.
In terms of structure, the central veins (venae centrales) form the centre of the lobule, whose edges are connected by the portal triads. A triad consists of branches of the hepatic artery and portal vein, and the bile canaliculi.
The liver's tissue can be divided into three kinds of unit:
- classic lobule,
- portal lobule and
- liver acinus.
The classic liver lobule can be seen as a roughly hexagonal cluster of tissue in the histological picture of the liver. It is based on the distribution of the branches of the v. portae and a. hepatica within the liver, and measures roughly 0.7×2.0 mm. At its centre lies the relatively wide central vein (vena centralis), into which the sinusoids drain. From here, the cell plates radiate out towards the periphery. The portal triads are found at the corners of the hexagon. Along its edges, between the connective tissue stroma and the hepatocytes, lie the so-called spaces of Mall.
The portal lobule performs the exocrine function of the liver– bile secretion. Its axis is therefore formed by the portal triad of the classic lobule and its interlobular bile duct, while its outer edges are imaginary lines drawn between three neighbouring central veins. These lines enclose a roughly triangular shape containing the bile-secreting parts of the classic lobules.
The liver acinus shows the best correlation between blood flow and liver pathology. It is a diamond-shaped unit whose short axis is formed by the terminal branches of the portal triad between two neighbouring classic lobules, and whose long axis is the straight line drawn between the two central veins closest to it.
The perisinusoidal space (space of Disse) is where substances are exchanged between the hepatocytes and the blood. It lies between the basal surface of the hepatocytes and the basal surfaces of the sinusoidal endothelial cells and Kupffer cells.
The livercells produce proteins and lipoproteins, which reach the blood through the space of Disse. The Kupffer cells found here form the lining of the sinusoids, and their processes project into the sinusoids. They can therefore take part in breaking down damaged and ageing red blood cells, which arrive here from the spleen via the portal vein (vena portae). The stellate cells (Ito cells) are also found here; they store vitamin A but, under pathological conditions, can turn into collagen-producing cells.
