Hepatic System Flashcards by Holly Grey

What is the hepatic system?

Liver + gall bladder

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What is the structure of the liver?

Highly vascularised 
4 lobes = 2 major + 2 minor
Well defined thin capsule of connective tissue
Rich in nerve endings 
Covered by single layer of mesothelium

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What are the 2 major lobes?

Left & right

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What are 2 minor lobes?

Caudate & quadrate

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What is the function of gall bladder?

Bile storage + secretion

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Where is gall bladder?

Under right lobe of liver

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What is the liver lobule?

Functional unit of the liver

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What is liver lobule structure?

Specialised epithelial cells + hepatocytes

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What is the liver lobule composed of?

Central terminal hepatic venule
Interconnecting places of hepatocytes
Peripherally arranged portal triad

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What are the hepatocyte zones in liver lobule?

Centrilobular, periportal + mid zone

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What are the 2 vessels the liver receives blood form?

Hepatic portal vein

Hepatic artery

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What does the portal vein do?

Conducts blood to liver + NOT directly to heart
Nutrient rich blood from digestive tract + spleen
Filters toxins from digestive tract

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What percentage of blood does portal vein supply to the liver?

75%

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What does the hepatic artery do?

Oxygenated blood supply from aorta

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What percentage of blood does hepatic artery supply to the liver?

25%

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Does the liver lobule have capillaries?

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What does the portal vein + hepatic artery discharge into?

Liver sinusoids

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What are the liver sinusoids lined with and why?

Phagocytes (Kupffer cells)

= destroy bacteria

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Where are pericytes found in sinusoids?

Disse (perisinusoidal space)

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What is stored in sinusoids?

Retinoid

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What does damage of sinusoids lead to?

Transdifferentiation into proliferative fibrogenic myofibroblasts + liver fibrosis

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What does bile canaliculi coalesce into?

Bile ductiles, running alongside portal veins

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Does blood + bile flow in opposite directions?

YES

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What are functions of the liver?

Detoxification + metabolism 
Decomposition of erythrocytes + excretion of bilirubin 
Cholesterol synthesis + lipogenesis 
Carbohydrate metabolism 
Protein synthesis 
Hormone production

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What does the liver store?

Glycogen Vitamin A, D, E, K + B12 Fe Cu

What is glycogenesis?

Synthesis of glycogen from excess glucose-6-phosphate

What happens in glycogenesis?

``` Glucose converted to G6P using 1x ATP G6P converted to G1P Activated by UTP=UTP-glucose UTP-glucose attaches to end of glucose chain UDP released (converted to UTP using ATP) ```

What happens in glycogenolysis?

Glucose phosphorylated when cleaved from glycogen to form G1P G1P ----> G6P, which enters glycolysis Phosphorylated glucose can't enter cells G6P hydrolysed to glucose

What is glycogenolysis activated by?

Glucagon in liver

What is glycogenolysis inhibited by?

Insulin

What is gluconeogenesis?

Glucose from non-carbohydrates

What molecules are considered glucogenic?

Any that can be converted to pyruvate | eg. lactate, alanine, glycerol

What is is the process of gluconeogenesis?

Reversible reactions of glycolysis

What 3 reactions are not reversible?

Hexokinase Phosphofructokinase Pyruvate kinase

What pathway is gluconeogenesis?

Red enzyme gluconeogenic pathway

What do red enzymes do?

Overcome high negative free energy of irreversible reactions of glycolysis

What is the Cori cycle?

Flow of lactate + glucose between muscles + liver

What happens in Cori cycle?

Lactate oxidised back t pyruvate in liver Gluconeogenesis converts pyruvate to glucose Transferred to muscles

What happens in liver metabolism?

Liver converts glucose via acetyl-CoA into fatty acids Retrieves FAs from lipids supplied with chylomicrons from intestine Converted into neutral fats + phospholipids VLDL formed

What is cholesterol used for?

Synthesis of bile acids, cell membranes + hormones

What happens to excess cholesterol?

Converted into bile acids or excreted with the bile

What are bile acids?

Steroids synthesised in liver from cholesterol

What is bile produced by?

Hepatocytes and passes into bile canaliculi

Where does bile canaliculi carry bile back to?

Portal triad

What is lipid digestion?

Bile facilitate solubilisation of dietary lipids during digestion by micelle formation

How is bilirubin formed?

Phagocytised + haemoglobin released

Describe process of bilirubin formation

Globin metabolised + amino acid recycled Fe bound to transferrin + returned to liver & BM Haem converted to bilirubin, bound to albumin

How is bilirubin metabolised in the liver?

Uptake of bilirubin by hepatocytes Bilirubin conjugated with 2 glucuronic acids by UDP -glucuronyl transferase Conjugate bilirubin transported into bile canaliculi + bile Intestinal bacteria degrade bilirubin + urobilinogen

What happens to bilirubin after it has been degraded?

80% oxidised to stercobilin + excreted in faeces | 20% enters extrahepatic circulation + excreted in urine

What is the first pass effect?

Substance absorbed from GI tract passes through liver

What are phase I reactions?

Metabolism

Describe what happens in phase I reactions

Convert parent compound into more polar molecule By adding or unmasking functional group Often metabolites inactive

Describe what happens in phase II reactions

Conjugation with endogenous substrate to increase aq solubility Conjugation with glucoronide, sulfate, acetate + amino acid

When do transaminases enzymes increase?

When liver is inflamed + damaged

When do cholestatic enzymes increase?

When biliary tract damaged + inflamed

Describe liver at foetal + newborn

1st trimester, liver main site of RBC production | By 32 weeks BM takes over

Describe liver at childhood

Liver produces insulin-like growth factor | Hormones plays role in childhood growth

Describe geriatric liver

Oxidative capacity of liver decreases with age | Reduced metabolism = longer drug exposure + reduced toxin clearance

What is hepatitis?

Inflammation of liver

What is cirrhosis?

Formation of fibrous tissue in liver replacing dead cells

What is haemochromatosis?

Excessive iron accumulation + liver damage

What is hepatic system cancer?

Hepatocellular carcinoma, cholangiocarcinoma

What is Wilson's disease?

Hereditary disease causing copper retention

What is biliary syndrome?

Genetic disorder of bilirubin metabolism

What is jaundice?

Yellow coloured skin, nail beds & sclera caused by deposition of bilirubin due to hyperbilirubinemia

What are the three types of jaundice?

Haemolytic Obstructive Hepatocellular

What is haemolytic jaundice?

Excessive RBC lysis

What is obstructive jaundice?

Conjugated bilirubin prevented from entering intestine

What is hepatocellular jaundice?

Liver damage causes low conjugation efficiency