Liver Flashcards
What is the location of the liver?
Located in the upper right quadrant of the abdomen, below the diaphragm, composed of thousands of polygonal structures called hepatic lobules (basic functional units).
What is the blood supply of the liver?
Has a dual blood supply via the hepatic artery and the hepatic portal vein. Hence it is supplied with a mixture of oxygenated and deoxygenated blood.
What is the function of the liver?
- Exocrine function: Secretion of bile into the duodenum to help digest fat and eliminate waste products, such as bilirubin and excess cholesterol.
- Endocrine function: Synthesis of majority of plasma proteins such as fibrinogen, prothrombin, lipoproteins, and albumins, and their release into the bloodstream.
- Metabolism and detoxification: Breakdown of proteins, toxic substances, and many drugs; oxidation and conjugation of toxins, and other hormones; and elimination via bile or urine.
- Storage: Storage of iron; blood; glycogen; triglycerides (lipid droplets); and vitamins A.
What are the main components of bile and what does it do?
water, bile salts, bilirubin, cholesterol, fatty acids, and electrolytes.
Bile acids/salts have an important function in emulsifying the lipids in the duodenum, promoting their digestion and absorption.
What are the constituents of a liver lobule?
- Hepatic lobule (central vein and portal area)
- Portal triad (bile duct, portal vein and hepatic artery)
- Sinusoids (emergence of artery and vein)
What type of cell is a kupffer cell?
Macrophage that shows star shaped
What are the constituents of a hepatocyte and what does it do?
- The bile canaliculi are enlarged intercellular spaces, located between two adjacent hepatocytes.
- The hepatic sinusoids carry glucose-rich and oxygen-rich blood to supply the hepatocytes through the space of Disse.
- Space of Disse (pink arrow) is between the endothelial cells of the hepatic sinusoid and the hepatocytes.
- Produces bile
Histological features of hepatocytes
Hepatocytes are large, polyhedral cells, the nuclei may vary in size, some cells are bi-nucleate.
Form plates/cords within liver
They store significant quantities of glycogen.
Route of bile in the liver
- Caniculi
- Canals of Hering, which are lined by cuboidal epithelial cells called cholangiocytes
- Bile ductules, which are located at the periphery of the tract
- Bile duct, which are line by simple columnar or cuboidal epithelium
- Gallbladder
What hormone regulates the release of bile from the liver and gallbladder?
cholecystokinin- Enteroendocrine cells in intestinal mucosa release cholecystokinin as fats in chyme enter duodenum.Cholecystokinin causes gallbladder contraction and expulsion of bile.
Histology of the portal tract
Liver organisation types (3)
- theclassic lobule(polygonal in shape) central vein in centre
- theportal lobule(triangular in shape) portal triad in centre
- theliver acinus(a diamond-shaped area that has three zones and best correlates to blood perfusion, metabolic activity, and liver pathology) zone 1 has greatest supply of blood
Hepatocyte and portal triad histology
(a) Hepatocytes (H) are polygonal epithelial cells, which form branching, irregular plates separated by venous sinusoids (S). (H&E X400)
(b) Reticulin (collagen type III) fibers (R) running along the plates of hepatocytes (H), supporting these and the intervening sinusoids. Most connective tissue in the liver is found in the septa and
portal tracts. (X400; Silver)
(c) With plates of hepatocytes (H) appearing to radiate from it, the central vein (C) of the lobule has more collagen than the smaller sinusoids (S) that drain into it from all directions (arrows). (X200;
Mallory trichrome)
(d) Peripheral portal areas contain more connective tissue and are the sites of the portal triad: a portal venule (PV), an arteriole branching off the hepatic artery (HA), and one or two bile ductules (BD). (X200; H&E)
What is the gallbladder and how is bile released?
- Hollow organ inferior to the liver designed to store and concentrate bile.
- Bile produced by liver hepatocytes is delivered by major excretory ducts.
- Connected to both liver and duodenum by the biliary duct system, the organ drains through the cystic duct, which joins the common hepatic duct to form the common bile duct.
- Bile is released in response to fats in the duodenum because of the action of cholecystokinin.
- Sphincter muscles relax and gallbladder contraction forces bile into the duodenum.
What is the flow of bile from the liver?
- Bile leaves the liver in the left and right hepatic ducts, which merge to form the common hepatic duct, which connects to the cystic duct serving the gallbladder. The latter two ducts merge to form a common bile duct. All these ducts carrying bile are lined by cuboidal or low columnar cells called cholangiocytes, similar to those of the small bile ductules in the liver.
- The main pancreatic duct merges with the common bile duct at the hepatopancreatic ampulla, which enters the wall of the duodenum at a major papilla (of Vater); the accessory pancreatic duct enters the duodenum at a minor papilla. Bile and pancreatic juices are mixed before release into the duodenal lumen.
What is the histology of the gallbladder?
- The gallbladder wall consists of three layers: a mucosa, a muscularis propria, and serosa.
- Mucosaof the gallbladder has numerous deep folds (to increase surface area), alamina propriarich in blood vessels, and a well-developedmuscularis externa(no muscularis mucosae or submucosa).
- Contraction of themuscularis externareduces the volume of the gallbladder, forcing bile out through the cystic duct and common bile duct to the duodenum.
- The bile produced by the hepatocytes flows through the bile canaliculi, bile ductules, and bile ducts. The hepatic, cystic, and common bile ducts are lined with a mucous membrane having a simple columnar epithelium of cholangiocytes.
