liver

Question 1

what are the main facts about the liver ?

Answer 1

. 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

Question 2

what are the main functions of the liver ?

Answer 2

. 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 )

Question 3

how many lobes does the liver contain ?

Answer 3

2

Question 4

what are the 2 lobes in the liver separated by ?

Answer 4

falciform ligament- separates the lobes and holds liver in place suspended below diaphragm

Question 5

what does each lobe contain ?

Answer 5

lobules

Question 6

what are liver lobules ?

Answer 6

liver cells that have a hexagonal structure - they are composed of blood vessel , bile canaliculi , blood vessels come together to form sinusoid

Question 7

what are lobules comprised of ?

Answer 7

hepatocytes which are surrounded by reticular fibre

Question 8

what do hepatocytes secrete ?

Answer 8

connective tissue - which supports blood vessel and bile duct and contains collagen - which contains proteoglycan for flexibility

Question 9

how does blood flow into the liver ?

Answer 9

blood comes in through the portal vein and hepatic artery

Question 10

explain the dual blood supply to liver ?

Answer 10

1. oxygen rich blood flows from the hepatic artery from the aorta
2. nutrient rich blood from portal vein that has just been through gastrointestinal tract

Question 11

where does blood from portal vein and hepatic artery mix?

Answer 11

in the hepatic sinusoids and blood flow past hepatocytes so they have both nutrient and oxygen rich blood

Question 12

how does blood exit the liver ?

Answer 12

through central vein

Question 13

who secretes bile ?

Answer 13

hepatocytes

Question 14

how does bile exit the liver ?

Answer 14

through bile ducts

Question 15

explain the structure hepatocytes ?

Answer 15

. hepatocytes have microvilli to increase surface area
. adjacent hepatocyte cells have tight junctions to prevent fluid flowing between hepatocytes
. bile canaliculi run between hepatocytes

Question 16

explain the structure of hepatic sinusoid ?

Answer 16

.they are blood vessels made up of endothelial cells

.they are fenestrated - allow easy flow of plasma but not erythrocytes

Question 17

what separates hepatocytes and hepatic sinusoids ?

Answer 17

they are separated by vasculature Disse’s space

Question 18

what Disse’s space ?

Answer 18

separates hepatocytes and hepatic sinusoid and contain plasma and dendritic cells

Question 19

function of dendritic cell ?

Answer 19

immune cells in Disse’s space which activate immune system

Question 20

what is the function of kupffer cells ?

Answer 20

.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

Question 21

explain carbohydrate metabolism in the liver ?

Answer 21

. store excess glucose as glycogen ( glycogenesis )
. break down of glycogen to glucose ( glycogenolysis )
. convert galactose and fructose to useable glucose
. gluconeogenesis

Question 22

what is the glucose buffer ?

Answer 22

1. high blood glucose level - liver - glycogen formation - normal blood glucose
2. fall in blood glucose level - liver - glycogenolysis - normal blood glucose

Question 23

what is gluconeogensis ?

Answer 23

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

Question 24

why do we need glucose ?

Answer 24

. 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

Question 25

how does triglyceride broken down ?

Answer 25

triglyceride + water ----------> 3 fatty acid + glycerol fatty acid - beta-oxidationto produce ATP glycerol - gluconeogenesis to produce glucose

Question 26

how does lipid metabolism occur in the liver ?

Answer 26

. 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

Question 27

how does protein metabolism occur in the liver ?

Answer 27

. 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

Question 28

what vitamins does the liver store ?

Answer 28

``` . vitamin A ( 10 month store ) . vitamin D ( 4 month store ) . vitamin B12 ( 1 year store ) . vitamin E and K . Folate ```

Question 29

what is the main ion stored in the liver ?

Answer 29

iron

Question 30

how is iron stored in the liver ?

Answer 30

. iron stored as part of the molecule ferritin in the liver | . iron in blood bound transferrin . binds with apoferritin in liver to form ferritin .

Question 31

when blood iron levels fall ?

Answer 31

when blood iron levels fall . ferritin releases free iron to bind to transferrin in blood

Question 32

what coagulation factors does the liver produce ?

Answer 32

1. factor VII 2. factor IX 3. factor X first 3 are activation proteins that activate clotting 4. fibrinogen 5. prothrombin last 2 are essential in clotting process in wound heeling

Question 33

explain liver detoxification ?

Answer 33

hepatocytes convert toxins into non-toxic metabolites which can be excreted from the body

Question 34

what are examples of toxins our body deals with ?

Answer 34

. breakdown products from hormones and neurotransmitters . drug . pollutants . insecticides and pesticides

Question 35

what are the two primary classes of chemical compound ( toxin)

Answer 35

1. hydrophilic ( dissolves in water ) polar : can be excretes in bile or urine 2. lipophilic ( dissolves in lipids ) non-polar : must be converted to hydrophilic to be excreted

Question 36

what are the two phases of converting lipophilic into hydrophilic ?

Answer 36

phase 1 : functionalisation | phase 2 : conjugation

Question 37

what happens in phase 1 functionalisation ?

Answer 37

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

Question 38

what happens in phase 2 conjugation ?

Answer 38

. more reactive molecules undergo conjugation reactions | . this makes the stable ( non-reactive ) but water soluble ( hydrophilic ) can be excreted via urine , bile and stool

Question 39

what does bile contain ?

Answer 39

``` . water . cholesterol . bile salts . buffering ions ( bicarbonate ) . bile pigment ( bilirubin and biliverdin ) ```

Question 40

what is the PH of bile ?

Answer 40

PH 8 | greeny yellow in colour

Question 41

what is the main function of bile ?

Answer 41

. secreted into duodenum | . aids in digestion of fats

Question 42

how is bile secreted ?

Answer 42

. bile is secreted by hepatocytes

Question 43

where does bile flow through when made by hepatocytes ?

Answer 43

. flows through bile canaliculi between cells . flows into common bile duct . stored in gall bladder

Question 44

what is secretion of bile into duodenum controlled by ?

Answer 44

. hormones : secretin , gastrin and somatostatin | . vagus nerve

Question 45

where are kupffer cells found ?

Answer 45

. adherent to sinusoidal epithelial cells inside the sinusoid

Question 46

what kupffer cells ?

Answer 46

resident liver macrophages