liver Flashcards
what are the main facts about the liver ?
. second largest organ in the human body
. make up 2-3% body mass
. it accounts for 20-30% of the total oxygen consumption-very metabolically active
. filters 1.4L blood every minute
what are the main functions of the liver ?
. metabolism
. uptake of nutrients delivered from the digestive tract via portal vein
. temporary nutrient storage ( glucose-glycogen)
. vitamin storage ( Fe reserve )
. produces coagulation factors- these are proteins flowing in plasma of blood ready to form clots
. detoxification - removal of toxins from blood - excretion of substance with bile, urine, faeces
.bile production
. kupffer cells ( macrophages )
how many lobes does the liver contain ?
2
what are the 2 lobes in the liver separated by ?
falciform ligament- separates the lobes and holds liver in place suspended below diaphragm
what does each lobe contain ?
lobules
what are liver lobules ?
liver cells that have a hexagonal structure - they are composed of blood vessel , bile canaliculi , blood vessels come together to form sinusoid
what are lobules comprised of ?
hepatocytes which are surrounded by reticular fibre
what do hepatocytes secrete ?
connective tissue - which supports blood vessel and bile duct and contains collagen - which contains proteoglycan for flexibility
how does blood flow into the liver ?
blood comes in through the portal vein and hepatic artery
explain the dual blood supply to liver ?
- oxygen rich blood flows from the hepatic artery from the aorta
- nutrient rich blood from portal vein that has just been through gastrointestinal tract
where does blood from portal vein and hepatic artery mix?
in the hepatic sinusoids and blood flow past hepatocytes so they have both nutrient and oxygen rich blood
how does blood exit the liver ?
through central vein
who secretes bile ?
hepatocytes
how does bile exit the liver ?
through bile ducts
explain the structure hepatocytes ?
. hepatocytes have microvilli to increase surface area
. adjacent hepatocyte cells have tight junctions to prevent fluid flowing between hepatocytes
. bile canaliculi run between hepatocytes
explain the structure of hepatic sinusoid ?
.they are blood vessels made up of endothelial cells
.they are fenestrated - allow easy flow of plasma but not erythrocytes
what separates hepatocytes and hepatic sinusoids ?
they are separated by vasculature Disse’s space
what Disse’s space ?
separates hepatocytes and hepatic sinusoid and contain plasma and dendritic cells
function of dendritic cell ?
immune cells in Disse’s space which activate immune system
what is the function of kupffer cells ?
.perform phagocytic function to remove protein complexes and small particles from the blood
. they also perform immune surveillance against toxic material from the gut and pathogens from the intestinal flora
explain carbohydrate metabolism in the liver ?
. store excess glucose as glycogen ( glycogenesis )
. break down of glycogen to glucose ( glycogenolysis )
. convert galactose and fructose to useable glucose
. gluconeogenesis
what is the glucose buffer ?
- high blood glucose level - liver - glycogen formation - normal blood glucose
- fall in blood glucose level - liver - glycogenolysis - normal blood glucose
what is gluconeogensis ?
alternative pathway to produce glucose from carbon skeleton
e.g amino acid - keto acid - glucose
. helps maintain systemic glucose level in liver so brain and muscles have sufficient supply to meet demand
why do we need glucose ?
. brain uses glucose as main energy source
. red blood cells rely on glucose as their only energy source
. glucose reserve of 190 g in glycogen store
. need 160 g glucose
how does triglyceride broken down ?
triglyceride + water ———-> 3 fatty acid + glycerol
fatty acid - beta-oxidationto produce ATP
glycerol - gluconeogenesis to produce glucose
how does lipid metabolism occur in the liver ?
. anabolism - synthesis of cholesterol and fatty acids
- synthesis of lipids from carbohydrates and amino acids ( lipogenesis )
. catabolism - beta oxidation of fatty acids to produce ATP
how does protein metabolism occur in the liver ?
. liver is the primary site of deamination of amino acids
. ammonia is turned into urea through urea cycle
. interconversion of amino acids ( transamination )
. site of plasma protein synthesis
what vitamins does the liver store ?
. vitamin A ( 10 month store ) . vitamin D ( 4 month store ) . vitamin B12 ( 1 year store ) . vitamin E and K . Folate
what is the main ion stored in the liver ?
iron
how is iron stored in the liver ?
. iron stored as part of the molecule ferritin in the liver
. iron in blood bound transferrin . binds with apoferritin in liver to form ferritin .
when blood iron levels fall ?
when blood iron levels fall . ferritin releases free iron to bind to transferrin in blood
what coagulation factors does the liver produce ?
- factor VII
- factor IX
- factor X
first 3 are activation proteins that activate clotting - fibrinogen
- prothrombin
last 2 are essential in clotting process in wound heeling
explain liver detoxification ?
hepatocytes convert toxins into non-toxic metabolites which can be excreted from the body
what are examples of toxins our body deals with ?
. breakdown products from hormones and neurotransmitters
. drug
. pollutants
. insecticides and pesticides
what are the two primary classes of chemical compound ( toxin)
- hydrophilic ( dissolves in water ) polar : can be excretes in bile or urine
- lipophilic ( dissolves in lipids ) non-polar : must be converted to hydrophilic to be excreted
what are the two phases of converting lipophilic into hydrophilic ?
phase 1 : functionalisation
phase 2 : conjugation
what happens in phase 1 functionalisation ?
enzymes : oxidoreductases e.g. cytochrome P450 and hydrolases introduce reactive/polar groups into toxins chemical structure
some become polar positive and are excreted through the kidney
what happens in phase 2 conjugation ?
. more reactive molecules undergo conjugation reactions
. this makes the stable ( non-reactive ) but water soluble ( hydrophilic ) can be excreted via urine , bile and stool
what does bile contain ?
. water . cholesterol . bile salts . buffering ions ( bicarbonate ) . bile pigment ( bilirubin and biliverdin )
what is the PH of bile ?
PH 8
greeny yellow in colour
what is the main function of bile ?
. secreted into duodenum
. aids in digestion of fats
how is bile secreted ?
. bile is secreted by hepatocytes
where does bile flow through when made by hepatocytes ?
. flows through bile canaliculi between cells
. flows into common bile duct
. stored in gall bladder
what is secretion of bile into duodenum controlled by ?
. hormones : secretin , gastrin and somatostatin
. vagus nerve
where are kupffer cells found ?
. adherent to sinusoidal epithelial cells inside the sinusoid
what kupffer cells ?
resident liver macrophages
