The Liver and Biliary System Flashcards
(20 cards)
Where is the liver located and what is its structure?
Right upper quadrant in close association with other abdominal organs. 1/50th of your body weight. It is composed of two segments separated by the falciform ligament.
Blood leaves the liver via the left hepatic vein.
The liver appears shiny due to a protective connective tissue layer.
Where is bile produced and what is its function?
Bile is produced by the gall bladder. It is secreted into the bile duct into the liver, which helps emulsify fat.
The liver is divided into segments what does each segment contain?
A lobule/acinus - the functional part of the liver.
These are composed of: plates of hepatocytes, sinusoidal channels, inlet and exit blood vessels and bile canaliculi.
Explain the livers blood supply
Portal vein - venous blood from gut (75%)
Hepatic artery - arteriole blood (25%)
25% of CO enters the liver = 1.3L/min
Blood enters, mixes in the sinusoids and drains via hepatic veins into the IVC near the right atrium.
What is the liver stroma composed of
ECM materials - dynamic and complex macromolecules mainly collagens (I, II, III, IV, V and VI) produced by satellate cells.
Glycoproteins link cells to collagen/ECM
Integrins - for bidirectional communication between cells.
Describe lobular organisation of the liver
The liver is organised into lobules around terminal branches of the hepatic vein. Between lobules are portal triads. Each triad consists of branches of a bile duct, portal vein and hepatic artery.
What is fibrosis and cirrhosis?
Conditions where there is irreversible scaring of the liver which forms de to the livers fast regenerative process. Blood pressure will start to build up as it cannot diffuse through it as well. It also leads to disruption of lobular architecture.
What cells are present in the liver?
Hepatocytes, epithelial cells, parenchymal cells, kupffer cells, satellate cells
Describe the hepatocytes and their function in the liver
60-65% of liver tissue = most abundant 100 billion cells Polarised polyhedral epithelial cells 20-30M in size Function: glucose is taken up by the cells and is converted into glycol polysaccharides for storage. These cells do most of the liver functions. Hepatocytes produce bile.
Describe biliary epithelium and their function in the liver
1-3% of liver tissue
Forms collecting vessels of increasing size to collect canalicular bile. Polarised cuboidal or columnar epithelial cells. Dense basement membrane to keep the bile in.
Describe the liver endothelium and its function
Squamous epithelial cells, line the hepatic vasculature. They protect the parenchyma from blood cells, bacteria and viruses. Selective uptake of solutes and particles and selectively allow immune component eg. leukocytes have to bind to enter.
Describe kupffer cells and their function in the liver
Kupffer cells are hepatic macrophages located within the sinusoids. Provide an immune response, they are 80% of all macrophages in the body.
Functions: phagocytosis, regulate microcirculation, removal of endotoxin.
Vey active receptor-mediated endocytosis. Can produce cytokines, present antigen and stimulate immune response.
Describe stellate cells and their function in the liver
Also called Ito cells or lipocytes. 15% of non hepatocyte cells in the liver. Perisinusoidal fat/retinoid storing cells. Star shaped with multiple membrane processes and branching structure. Can transform to a more fibroblast like morphology in disease.
They store useful lipids.
What is the function of the liver
Bile production Detoxification of alcohol Immune regulation Production of clotting factor Production of glucose
What is the digestive function of the liver?
Carbohydrate and fat metabolism. Storage of vitamins and minerals. Haemochromatosis is storing of iron.
Why is cholesterol important?
Essential component of cell membranes- it establishes proper membrane permeability and fluidity.
An important component in the production of bile acids, steroid hormones and vitamin D.
Production of bile and its function
The liver produces about 0.5L of bile a day by hepatocytes. The bile is recycled 6-8 times a day to recycle the bile salt which could run out otherwise. A few 100ml can be stored in the gall bladder and released into the intestine upon demand.
Bile is involved in the emulsification of fat in the intestine. Fat soluble vitamin uptake (A, D, E, K). Also used for excretion of some substances which cannot be cleared by the kidneys.
Describe the immune function of the liver
Protection against pathogens is required as bacteria is often among the portal blood entering the liver. Kupffer cells are specialised phagocytic macrophages located in the liver, which engulf and digest these intestinal bacteria. Under the microscope kupffer cells appear black cells and an asymmetrical shape.
Explain detoxification and elimination functions of the liver
Urinary excretion = solubilisation of compounds
Biliary excretion = lipophilic comounds
Drugs require a biotransformation:
Phase 1: Oxidation or reduction to make soluble (P450)
Phase 2: Conjugation to make water soluble
CYPs are the major enzymes involved in drug metabolism and deactivation - either directly or by facilitated excretion from the body.
Levels of P450 change as you age. Dosage needs to be more carefully monitored.
What proteins are synthesised in the liver?
Albumin (50% of all plasma proteins), fibronectin, plasminogen, alpha-1 antitrypsin, transferrin, hepcidin.
