Liver is the largest glandular organ of human body. It is reddish brown in colour. Its weight about 1.5 kg. It lies in upper right portion of the abdomen. It develops from endoderm. It has 4 lobes- right lobe, left lobe, quadrants and caudal lobe. Gall bladder lies on the ventral side of liver. Gall bladder stores bile secreted by liver. Bile enters the gall bladder through hepatic ducts and passes into common bile duct through cystic duct. The common bile duct joins with a single pancreatic duct or duct of Wirsung to form ampulla of Vater or hepatopancreatic duct which opens into duodenum through duodenal papillae. Its opening is encircled by sphincter of Oddi.
Liver gets 25% blood from the hepatic artery and 75% blood enters it from the hepatic portal vein that is formed from the alimentary canal.Venous blood from liver passes into inferior vena cava through hepatic vein.
Histology of Liver:
The lobes of liver are organized into liver lobules. The liver lobules are functional unit of liver.Each lobule is surrounded by connective tissue partition called Glisson’s capsule. The capsule contains branches of portal vein, hepatic artery and bile ducts. Each lobule has a central vein at its center. Around the central vein hepatic chords or plates are radiated. A hepatic chord is formed of hexagonal liver cells or hepatocytes. The space between hepatic chords called sinusoid. Sinusoids are lined by endothelial cells. Some of these endothelial cells phagocytose dead RBC, bacteria and foreign particles.
These phagocytic cells are called Kupffer’s cells.t liver cells are surrounded by bile capillaries or canaliculi which unite peripherally to form bile duct. Blood flows centripetally from branches of portal vein and hepatic artery to central vein via sinusoids but bile flows centrifugally from bile canalicule to bile ducts. The central veins unite to form hepatic vein and the bile ducts in turn unite to form hepatic duct in each lobe. The hepatic ducts on both sides unite to form common hepatic duct.
Function of Liver:
1. Bile secretion: Liver secrets bile. Bile is an alkaline fluid that makes the medium in the intestine alkaline. It is antiseptic and it emulsifies the fat.
2. Glycogenesis: Liver cells synthesize glycogen from glucose.
3. Glyconeogenesis: Liver cells synthesize carbohydrates from non-carbohydrates like amino acids and fatty acids.
4. Glycogenolysis: Liver cells break down glycogen into glucose when glucose level in the blood decreases.
5. Lipogenesis: They synthesize lipids.
6. Vitellogenesis: They synthesizes yolk in female.
7. De-amination: Liver cells remove amino groups from excessive amino acids in blood.
8. Ureogenesis: Liver cells synthesize urea from ammonia.
9. Detoxication: They detoxify the toxic substance produced during metabolism.
10. Haematopoietic organ: Liver produces RBCs in embryo.
11. Haemolytic: The endothelial cells break down worn out and dead RBCs.
12. Phagocytic: Kupffer cells phagocitise bacteria and foreign bodies.
13. Glucostatic: Liver cells uptake glucose is highd discharge when it is low. Hence, liver functions absent a sort of glucostat. This process is hormone dependent.
14. Reservoir of vitamins: Liver cells synthesize vitamin- A and store vitamin- A,D,B12 and K.
15. Synthesis of coagulants: Liver cells synthesizes blood coagulating proteins like prothrombin and fibrinogen.
16. Synthesis of anticoagulant: They synthesize anticoagulant heparin which prevents coagulation or clotting of blood in blood vessels.
17. Enzyme synthesis: Liver cells synthesize certain enzymes (e.g. arginase) for protein, carbohydrates and fat metabolism.
18. Store-house of blood: Liver stores 450 ml of blood in its sinusoids.
19. Stores iron and copper: Liver contains iron storing protein ferritin.