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Gastroenterology > Hepatobiliary System > Flashcards

Hepatobiliary System Flashcards

1
Q

What are the upper and lower limits of the liver

A

Nipple and subcostal margin

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2
Q

What are the inflows and outflows of the liver

A

Inflow - Hepatic artery (25%), portal vein (75%)

Outflow - Bile, 3x hepatic veins

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3
Q

What is the purpose of blood delivered to liver by:

portal vein?

hepatic artery?

A
  1. From digestive system
  2. Supply oxygen and nutrients
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4
Q

Where is the 1st segment of the liver

A

Behind portal vein in front of vena cava

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5
Q

What is the micro-function of the liver

A

Acinus

Blood flow

Bile flow

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6
Q

What is the micro-morphology of the hepatic lobule

A

Hexagonal structural unit of liver tissue

Each corner consists of a portal triad - links with 3x adjacent lobules

Centre of liver lobule is a central vein - collects blood from hepatic sinusoids

Within lobule there are rows of hepatocytes - sinusoid facing side and bile canliculi facing side

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7
Q

What is the micro-morphology of portal triad

A

Branch of hepatic artery - O2 rich blood to support hepatocytes

Branch of portal vein - mixed venous blood from GIT (nutrients, abcteria nad toxins) and spleen (waste products), Bile duct - bile produced by liver drain into bile canliculi, coalesce with colangiocyte-lined bile ducts are lobule perimeter

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8
Q

What is the hepatic acinus

A

FUnctional unit of the liver

Consists of two adjacent 1/6th hepatic lobules

  • Share 2 portal triads
  • Extend into hepatic lobules as far as central vein
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9
Q

What is the three zone model of hepatic acinus

A

Blood into hepatic acinus via point A

Blood drains out of hepatic acinus via point B

Hepatocytes near outer hepatic lobule receive early exposure to blood contents - o2 but also toxins

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10
Q

What are the sinusoidal endothelial cells

A

No basement membrane

Fenestrated (discontinuous endothelium)

Allow lipid and large molecule movement to and from hepatocytes

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11
Q

What are kuppfer cells

A

Sinusoidal macrophage cells

Attatched to endothelial cells

Phgocytosis (eliminate substances arriving from portal circulation)

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12
Q

What are hepatic stellate cells

A

Exist in dormant state

Store VIt A in liver cytosolic droplets

Activated (fibroblasts) in response to liver damage

Proliferate, chemotactic and deposit collagen in ECM

Collagen cause damage cirrhosis

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13
Q

What are hepatocyte cells

A

Synthesis e.g. albymin, clotting factors and bile salts

Drug metabolism

Receive nutrients and building blocks from sinusoids

80% of liver mass

Cubical

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14
Q

What are cholangiocyte

A

Secrete HCO3 and H2O

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15
Q

What are the hepatocyte functions

A

Metabolic and catabolic functions: synthesis carbs, lipids and proteins

Secretory and excretory functions: syntehsis of proteins, bile and waste products

Detoxification and immunological functions: breakdown of ingested pathogens and processing of drugs

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16
Q

Where does anaerobic conversion of glucose happen

A

RBCs, renal medulla and skeletal muscle

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17
Q

Where does aerobic oxidation of glucose

A

CNS, heart, skeletal muscle, most organs

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18
Q

What is the cori cycle

A

Lactate to pyruvate using lactate dehydrogenase

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19
Q

Diagram of hepatocyte function - protein synthesis

A
20
Q

Synthesis of non-essnetial amino acids

A
21
Q

Different keto-acids being converted into multiple amino acids

A

alpha-keto glutarate - glutamate, proline, arginine

Pyruvate - alanine, valine, leucine

Oxaloacetate - aspartate, methionine, lysine

22
Q

How do you resolve the issue that muscle can potentially utilise amino acids to produce glucose for energy

A

Convert pyruvate to glucose requires energy

Removing nitrogen as urea requires energy

Solution: transfer problem to the liver (glucose-alanine cycle)

23
Q

What can alanine be converted to in the liver

A

Glutamate 0 can be converted to urea or combined with alpha ketogutarate to use in kreb cycle

Alpha ketoglutarate

Pyruvate

24
Q

Diagram of triglyceride metabolism in liver

A
25
Q

What can acetyl CoA produce in the liver

A

Fatty acids

Cholesterol

26
Q

How do you make lipoproteins in teh liver

A

Glycerol, tri-acyl glycerol, apoproteins, phospholipids, cholesterol, fatty acids

27
Q

What is one of the major roles for cholesterol in the cells

A

Maintain cell membrane, make hormones

28
Q

How are the liporoteins in the liver used

A
29
Q

What deos the liver store

A

Fat soluble vitamins (A,D,E,K) - sufficient for 6 months except for vit K essential for blood clotting

Storage of iron as ferritin (available for erythropoeisis)

30
Q

How does the liver detoxify

A

Phase 1 (modification_ - P450 enzymes - makes molecules more hydrophilic

Phase 2 (conjugation) - attach water soluble side chain to make less reactive

31
Q

What is the composition of bile

A
32
Q

What are the uses of bile

A

Cholesterol homeostasis

Absorption of lipids and lipid soluble vitamins (A,D,E and K)

Excretion of

  • drugs
  • xenobiotics
  • cholesterol metabolites
  • adrenocortical and otehr steroid hormones
  • alkaline phosphatase
33
Q

What is the primary secretion of bile

A

Hepatocytes (60%)

  • Bile secretions reflect serum concentrations

Secretion of bile salts, lipids and organic ions

34
Q

What is the secondary modifaction of bile

A

Cholangiocytes (40%)

  • Alteration of pH
  • H20 drawn into bile by osmosis via paracellular junctions
  • Luminal glucose and organic acids reabsorbed
  • HCO3 and Cl actively secreted into bile by CFTR (cystic fibrosis transmembrane regulator)
  • IgA exocytosed
35
Q

What are the facts about production of bile

A

500mls produced each day

Bile is yellow/green due to pigments such as billirubin and biliverdin

36
Q

What are the main transporters of biliary system

A

Bile Salt Excretory Pump

MDR related proteins (MRP1 nad MRP3)

Products of familial intrahepatic cholestasis gene (FIC1)

Products of mulitdrug resistance genes (MDR1(xenobiotics and cytotoxins) and MDR3(phospatidylcholine))

37
Q

How does bile salts perform its function

A

Form micelles

Hydrophilic domain - faces out, dissolves in water

Hydrophobic domain - nucleus and methyl - faces in and dissolves fat

38
Q

What enzymes convert triglyceride to fatty acids

A

Lipase and colipase

39
Q

How does the regulation of bile flow happen

A

Between meals Sphincter of Oddi is closed - bile diverted into gall bladder

Eating - sphincter of oddi relaxes

Gastric contents enter duodenum causing release of cholecystokinin (CCK)

CCK causes gall bladder to contract

40
Q

What happens during bile salts after entering the GIT

A

95% reabsorbed by terminal ileum by Na+/bile salt cotransport Na+K+ ATPase system

5% coverted to secondary bile acids in colon - deoxycholic acid is absorbed wheras 99% lithocolic acid excreted

absobred B salts back to liver

41
Q

What are the fucntions of gallbladder

A

Stores bile - concentrates bile/ acidifies bile

GB contraction triggered by CCK, CCKa receptors and neuronal plexus of GB wall (innervated by parasympathetic fibres of vagus nerve)

42
Q

Where is bilirubin derived from

A

75% from Hb breakdown

22 from catabolism of otehr haemoproteins

3% from ineffective BM erythropoiesis

Free BR - H20 insoluble, yellow pigment

43
Q

How is bilirubin excreted

A

85% excreted in faeces - (BR-urobilinogen-stercobilinogen-stercobilin (brown compound))

15% enters enterohepatic circulation - deconjugated into lipophilic form of stercobilinogen, urobilinogen

1% enters systemic circulation and excreted by kidneys

44
Q

What are some causes of jaudice

A

Hemolysis

Decrease uptake, conjugation and secretion of bilirubin

Extrahepatic outflow

45
Q

What is a endoscopic retrograde cholangiopancreatography

A

It is used to diagnose biliary and pancreatic duct systems using endoscopy and fluoroscopy

46
Q

What is a percutaneous transhepatic cholangiography

A

Radiology to visualise anatomy of the biliary tract

Gastroenterology (9 decks)

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