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Mona Theodoraki

Organisation Of The Liver Morphological Anatomy

Liver under right diaphragmatic dome, in right upper quadrant Surrounded by ribs and dome of diaphragm Capsule of liver very nerve rich so lots of pain when liver damaged Blood Supply Of The Liver Rich blood supply – 25% of resting cardiac output Dual blood supply – difficult for liver to become ischaemic 20% arterial blood from hepatic artery (left and right branches) 80% venous blood draining from gut through hepatic portal vein HPV drains gut – blood rich in absorbed nutrients which must pass through liver Lobes Of The Liver Anatomical lobes based on attachment of mesenteries Boundary between territories of left and right branches of hepatic artery is important Puts small lobes (caudate and quadrate) in with functional left lobe Functional Anatomy Couinaud classification 8 functionally independent segments Centrally – portal vein, hepatic artery and bile duct Peripherally – hepatic vein Each segment can be resected without damaging those remaining Numbered clockwise Caudate lobe (segment 1) is posterior Anatomical variants frequently occur Embryological Origins Liver and biliary system share common origin with ventral part of pancreas at beginning of midgut Septum transversum arises at embryonic junctional site – where ectoderm of amnion meets endoderm of yolk sac (externally), where foregut meets midgut (internally) Mesenchymal structure of septum transversum provides support upon which liver and blood supply can develop


Mona Theodoraki Biliary Tract Biliary tract has spiral muscle structure which twists and untwists As it untwists it becomes patent (expanded/open) and allows bile to pass through Biliary obstruction results in jaundice (see previous lecture) Histological Structure Liver consists of lobules consisting of cords (sheets) of liver epithelial cells (hepatocytes) Radiate from central vein (draining via main hepatic veins to IVC) Round the edges of adjoining lobules are portal triads Portal triads consist of – arteriole, branch of portal vein, bile duct All come from main triad entering liver at porta or hilum Liver Cell Types Hepatocytes – 80% Endothelial cells – lining blood vessels and sinusoids Cholangiocytes – lining biliary structures Kupffer cells – fixed phagocytes (liver macrophages) Hepatic stellate cells – vitamin A storage cells, may be activated to fibrogenic myofibroblastic phenotype Hepatocyte sheets near central vein of lobule Flattened dense cell nuclei belong to phagocytic Kupffer cells Hepatocyte nuclei are paler and rounded Lobule Vs. Acinus Lobule Histological (morphological unit) Easily identified Hepatic vein at centre Acinus Functional unit Less clearly identified Unit of hepatocytes aligned around hepatic arterioles and portal venules Acinus divided into zones dependent on proximity to arterial blood supply


Mona Theodoraki

Liver Functions Most functions carried out by hepatocytes Breakdown and recycling of red cells carried out by fixed macrophages (Kupffer cells) in endothelial lining of blood sinusoids Sinusoid – small blood vessel similar to capillary but with fenestrated endothelium Large multifunctional organ Functions carefully regulated to meet body requirements Key role in – digestion, biosynthesis, degradation and detoxification, energy and metabolism Space Of Disse Space of Disse – location in liver between hepatocyte and sinusoid Contains blood plasma Microvilli of hepatocytes extend into this space, allowing proteins and other plasma components from sinusoids to be absorbed by hepatocytes Space may be obliterated in liver disease, leading to decreased uptake by hepatocytes of nutrients and wastes (eg. bilirubin) Space of Disse has phagocytes Liver Structure In Disease Activated stellate cells Deposition of scar matrix Loss of fenestrae in hepatic Kupffer cell activation Loss of hepatocyte microvilli

sinusoid


Mona's SAMPLE Alimentary  

Mona's SAMPLE Alimentary

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