Normal liver physiology Flashcards
What is the blood supply to the liver?
Hepatic portal vein (SMV, IMV and Splenic Vein) Hepatic artery (from Coeliac Trunk)
What are the key functional zones of the liver?
Zone 1 - periportal hepatocytes (outermost and most oxygenated) - specialise in oxidative metabolism, gluconeogenesis and urea synthesis
Zone 3 - pericentral hepatocytes - specialise in drug metabolism, glycolysis and lipogenesis
What are sinusoids?
Vascular spaces running between plates of hepatocytes
Lined with epithelial cells
Are are the major cell types of the liver?
Hepatocytes
Cholangiocytes
Reticuloendothelial cell meshwork (made up of endothelial cells, Kupffer cells and lipocytes)
What is the function of cholangiocytes?
Line bile duct and secrete bicarbonate ions and water into the bile
What is the function of endothelial cells in the reticuloendothelial cell meshwork?
Line sinusoids
What is the function of Kupffer cells in the reticuloendothelial cell meshwork?
Immune cells anchored to the walls of sinusoids
Phagocytose bacteria and ingest inflammatory mediators
What is the function of lipocytes in the reticuloendothelial cell meshwork?
Found in space of Disse (between hepatocyte plate and sinusoid)
Storage of fat
What cells are affected in Cirrhosis?
Lipocytes - secrete collagen affecting structure of liver
What are the major functions of the liver?
DESPICES:
Drug metabolism and detoxification Energy metabolism and substrate interconversion Synthesis of plasma proteins Production of bile Immune functions Cholesterol processing Excretion of bilirubin Storage of vitamins and minerals
What molecules are metabolised for energy in the liver?
Carbohydrates (glycogenolysis, gluconeogenesis, glycogen synthesis, glycolysis)
Lipids (ketogenesis, triglyceride synthesis from fatty acids)
Proteins (deamination, urea formation)
What is the major plasma protein and its function?
Albumin
Able to carry various proteins and maintain osmotic pressure of plasma
Transports molecules in blood
What factors are synthesised in the liver for haemostasis and fibrinolysis?
Fibrinogen (for coagulation)
Alpha-1 antitripsin (coagulation inhibitor)
Plasminogen (fibrinolysis)
What carriage/ binding proteins are synthesised in the liver?
Transferrin (carries iron)
Sex hormone binding globulin
Thyroid-binding globulin
What are apolipoproteins?
Synthesised in liver
Bind lipids to form lipoproteins for transportation of lipids through lymphatic and circulatory systems
Where does cholesterol come from?
15% from diet
85% synthesised in body
What vitamins and minerals are stored in the liver?
Fat soluble vitamins: A, D, E, K
Minerals: Iron, Copper
How is bilirubin excreted?
Conjugated with glucoronic acid by hepatocytes to allow it to be exported into bile
What is bilirubin?
Bile pigment formed from the breakdown of red blood cells into haem in the spleen and bone marrow
Where is bile produced and stored?
Produced in liver
Stored in gallbladder (where water and salts are drawn out to increase concentration)
How much bile is secreted per day?
0.7-1.2 litres
What are the 6 major components of bile?
- Bile salts
- Lecithin
- Bicarbonate ions
- Cholesterol
- Bile pigments
- Trace metals
What are the functions of bile salts?
Conjugated to taurine to increase solubility (become conjugated bile salts)
Exported down bile canaliculus to be excreted
Work to emulsify and digest fats in small intestine
What is the fate of bile salts?
95% returned to liver via portal circulation
5% excreted in faeces