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GI Final > Hepatobiliary Function > Flashcards

Hepatobiliary Function Flashcards

1
Q

Main Function of Liver

A
  • absorbed nutrients and detoxify ingested and/or toxins
  • detoxification of substances
  • metabolism of CHO, proteins, lipids, and many hormones
  • bile production and secretion
  • bilirubin production, conjugation, & excretion
  • filtration of storage of blood
  • storage of vitamin A and iron
  • formation of coagulation factors
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2
Q

Metabolic Functions of the Liver

  • carbohydrate (3)
  • protein (4)
  • lipid (2)
A

Carbohydrate

1) Storage of glucose as glycogen
2) Gluconeogenesis and release of glucose
3) convert fructose and galactose to glucose

Protein

1) synthesis of nonessential AA
2) modification of AA for use in biosynthetic pathways for carbohydrates (deamination)
3) Synthesis of plasma proteins (albumin & clotting factors)
4) Conversion of ammonia to urea

Lipid

1) Synthesis of lipoproteins, cholesterol, and phospholipids
2) Fatty acid oxidation & de novo lipogenesis

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3
Q

Liver Failure

A

result in hypoalbuminemia

lead to edema

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4
Q

Hepatic portal system : two capillary beds

A

1) abdominal and pelvic parts of the gut from the abdominal part of the esophagus to lower anal canal ( together with pancreas, gallbladder, and spleen)
2) hepatic sinusoidal “capillary” bed

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5
Q

Cirrhosis

  • describe
  • cause
A

chronic liver disease in which normal liver cells are damaged and replaced by scar tissue (fibrosis)

  • due to excessive alcohol intake/ alcohol abuse
  • > accumulation of fat within hepatocytes -> steatohepatitis ( fatty liver accompanied by inflammation-> scarring of liver and cirrhosis)
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6
Q

Portal Hypertension

  • describe
  • location
  • causes
  • relationships
A

increased resistance to portal blood flow

occurs in liver

cirrhosis can cause portal HTN

More parallel=lower resistance
more series= greater resistance

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7
Q

Primary biliary Cirhosis

A

chronic disease that causes the bile ducts in the liver to become inflamed, damaged, and are eventually lost

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8
Q

Circulation of Liver

  • inputs
  • outputs
A

lots of blood 27% of Q

Inputs:

  1. hepatic portal vein- nutrient rich blood from GI, low O2
  2. hepatic artery- O2 rich from systemic circulation

Outputs:

  1. hepatic ducts for bile excretion
  2. hepatic vein- low O2 to vena cava
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9
Q

Consequences of Portal Hypertension (6)

A

increased hydrostatic pressure OR decreased oncotic pressure is culprit

1) ascites
2) esophageal varices
3) hepatic encephalopathy
4) malnutrition
5) skin spider angiomata, periumbilical caput medusa
6) Hemorrhoids

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10
Q

Esophageal varices

A

swollen connection betwen systemic and portal systems at inferior end of esophagus

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11
Q

Caput medusae

A

swollen connections between systemic and portal systems around umbilicus

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12
Q

how liver dysfunction can lead to hepatic encephalopathy?

A

decreased hepatic urea cycle metabolism in the context of liver cirrhosis or portosystemic shunting leads to accumulation of ammonia in the systemic circulation
- ammonia readily crosses the blood-brain barrier and alters brain function

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13
Q

Bile

  • where it is produced and secreted
  • composition (6)
  • function
A

Liver

Composition

  1. Bile Salts (50%)
  2. Bile pigment (2%)
    - bilirubin
  3. cholesterol (4%)
  4. Phospholipids, such as lecithin (40%)
  5. Ions
  6. Water

Function

  1. Vehicle for elimination of substances from body
  2. Solubilizes lipids that are naturally insoluble
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14
Q

Bile Canaliculi (canalicular bile )

A

secreted by ductule cells in response to osmotic effects of anion transport

where newly synthesized and returning bile acids

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15
Q

Formation of bile salt

  • pathway
  • types of bile acid
A

cholic acid-> chenodeoxycholic acid-> deoxycholic acid-> lithocholic acid

primary bile acids synthesized in hepatocytes

secondary bile acids synthesized in lumen small intestine

Bile salts conjugated in liver

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16
Q

what do bile salts form?

A

micelles with products of lipid digestion

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17
Q

Biliary System’s Organs (5)

-function of overall organs

A
  1. Liver
  2. Gallbladder & bile duct
  3. Duodenum
  4. Ileum
  5. Portal Circulation
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18
Q

Mechanism of bile secretion & absorption of bile salts

- 5 steps

A

1) Synthesis and secretion of bile salts
2) Bile salts are stored & concentrated in gallbladder (absorption of ions & H2O)
3) CCK- induced gallbladder contraction & sphincter of Oddi relaxation
4) Absorption of bile salts into portal circulation
5) Delivery of bile salts to liver

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19
Q

Enterohepatic Circulation:

-steps

A

recycles bile acid/salts by returning bile salts to liver to be reused

1) Bile salts use portal circulation via transport in terminal ileum
2) Bile salts back to liver
3) some bile salts are lost in feces and replaced by synthesis of new bile

20
Q

Where are bile salts secreted? are they secreted actively or passively?

A

Secreted actively across canalicular membrane

21
Q

Bile salt + newly synthesized bile acid=>

A

returning bile acids are secreted into bile canaliculi

22
Q

when are canalicular bile secreted?

A

by ductule cell in response to osmotic effects of anion transport

23
Q

Bile Salt Transporters

  • Uptake into hepatocytes (2)
  • Uptake into caniculi (2)
  • into enterocytes
  • exit enterocytes
A

Uptake into heptaocytes

  1. NTCP- Na dependent transport protein
    - sodium taurocholate cotransporting polypeptide
  2. OATPS *- organic anion transport protein

Uptake into caniculi

  1. BSEP- bile salt excretory pump
  2. MRP2- multidrug resistance protein 2

Into Enterocytes
- ASBT- apical sodium dependent bile acid transporter

Exit Enterocytes
- OST alpha/beta : organic solute tranporter alpha beta

24
Q

Where is bile salt recycling mostly in?

A
  • Ileal transport process (90%)
    • bile acids to portal blood
  • feces (5-10%)
25
Q

Effects of increased bile secretion

- which hormone

A

increase rate of return

negative feedback on synthesis

Cholesterol 7a- hydroxylase is inhibited by bile salts

26
Q

Bile formation is driven by..?

A

bile acids

27
Q

Secretin on bile

- effects

A

secretin stimulates HCO3 & H2O secretion from ductile cell

  • increase bile volume, HCO3 conc, pH
  • decrease bile salt con
28
Q

Bile flow during period of digestion:

1) interdigestive period
2) On eating

A

Interdigestive period

  • gallbladder fills with bile
  • gallbladder is relax
  • sphincter of Oddi is closed

On eating
CCK mediated
- contraction of bladder
- relaxation of sphincter of Oddi

29
Q

Bilirubin Production & Excretion

  • very important!
  • pathway
A

in RBC
Hemoglobin-> Biliverdin -> Bilirubin-> Bilirubin-albumin (transport to liver)

Liver
uncojugated Bilirubin (UDP glucuronyl transferase)-> conjugated bilirubin -> conjugated bilirubin+ bile

SI/ Colon
Conjugated bilirubin -> Urobilinogen-> Urobilin , stercobilin-> excreted feces

30
Q

If bilirubin is not excreted in feces, what happens?

A

will return to liver via enterohepatic circulation

31
Q

Liver Function Test

A

NOT AN ACTUAL TEST OF FUNCTIONALITY

  • biochemical and function test
  • pretty imprecise bc it does not reflect health of liver
32
Q

Liver Enzymes measured in serum

- if enzymes are elevated, what do they suggest?

A
  1. Aminotransferases:
    - alanine aminotransferase (ALT)
    - aspartate aminotransferase (AST)
    - – if elevated=> hepatocyte injury
  2. Alkaline phosphatase (Alk Phos)
    - – if elevated => cholestasis (gallstones)
33
Q

Jaundice

  • nickname
  • causes (5)
  • hereditary defects (5)
A

aka Icterus

Hyperbilirubenemia

  1. excess bilirubin (hemolytic anemia
    - unconjugated
  2. decreased bilirubin uptake bilirubin into hepatocytes
    - uncojugated
  3. disturbed intracellular protein binding or conjugation
    - uncojugated or conjugated
  4. disturbed secretion of conjugated bilirubin into bile canaliculi
    - conjugated
  5. intrahepatic or extrahepatitic bile duct obstruction
    - conjugated
Defects
1. Gilbert's Syndrome
2. Dubin-Johnson Syndrome
3. Rotor Syndrom
4. Crigler- Najjar syndrome Type 1
5. Crigler- Najjar syndrome 
Type 2
34
Q

Bilirubin pathway

A
  1. RBC breakdown-> 2. unconjugated bilirubin delivery to liver-> 3. uptake to liver-> 4. conjugated bilirubin -> 5. secretion into bile -> 6. passage of bile
35
Q

Hemolytic Anemia

  • which pathways is defected
  • effects on bilirubin
A
  1. RBC breakdown

form of anemia due to hemolysis ( too much RBC)

increased unconjugated bilirubin

no change in conjugated bilirubin

36
Q

Neonatal Jaundice

  • which pathways is defected
  • effects on bilirubin
  • causes
  • treatment
A
  1. RBC breakdown
  2. uptake to liver

increased unconjugated bilirubin in blood suring 1st week

Infants are tired and feed poorly

Causes:

1) increased bilirubin production due to breakdown of fetal erythrocytes (unconjugated bilirubin)
2) low activity of UDP glucuronyl transferase

Treatment

  • Phototherapy
    • if bilirubin >21 mg/dl
    • works to change trans-bilirubin into water-soluble cis-bilirubin isomer
37
Q

Gilbert’s Syndrome

  • which pathways is defected
  • effects on bilirubin
A
  1. Conjugated bilirubin

30% of ppl asymptomatic
-seen during adolescence

mutation in gene that encodes UDP-glucoronyl transferase

  • hyperbilirubinemia

INCREASE unconjugated bilirubin
- no change in conjugated bilirubin

38
Q

Crigler- Najjar Syndrome

  • which pathways is defected
  • effects on bilirubin
A
  1. Conjugated bilirubin

mutation in gene that encodes for UDP-glucuronyl transferase

-nonhemolytic jaundice

  • increased levels of unconjugated bilirubin
  • no changes in conjugated bilirubin

Type 1- more severe
Type 2- less severe

39
Q

Criggler Najjar Syndrome Type 1

  • which pathways is defected
  • effects on bilirubin
  • treatment
A
  1. Conjugated bilirubin

starts earlier in life
- Jaundice apparent at birth or in infancy

KERNICTERUS- form of brain damage caused by accumulation of unconjugated bilirubin in regions of brain

Treatment:

  • Phototherapy- can be up to 12 hr/d
  • heme oxygenase inhibitors, oral calcium phosphate anda carbonate, liver transplantation
40
Q

Criggler Najjar Syndrome Type 2

  • which pathways is defected
  • effects on bilirubin
  • treatment
A
  1. conjugated bilirubine

later in life-> survival into adult hood

less than 20% function of UDP- glucoronyl transferase

less likely to develop kernicterus

Therapy

  • PHENOBARBITOL
    • treat type 2 to aid in conjugation of bilirubin ( no response in patients with Type 1)
41
Q

Kernicterus

  • describe
  • clinical features
A

permanent neurologic sequelae of bilirubin induced neurologic dysfunction

develops during 1st year PN

Clinical PResentation

  • cerebral palsy
  • sensory neural hearing loss
  • gaze abnormalities
42
Q

Dubin-Johnson Syndrome

  • which pathways is defected
  • causes
A
  1. secretion into bile

mild jaundice throughout life

  • may not appear until puberty or adulthood
  • may be worsened with alcohol, birth control pills, infection, pregnancy

defect in ability of hepatocytes to secrete conjugated bilirubin into bile
- MUTATIONS in MRP2

liver has black pigmentation - result of an intracellular melanin-like substance

43
Q

Rotor Syndrome

  • which pathways is defected
  • causes
  • bilirubin effect
A
  1. liver uptake
  2. conjugated bilirubin
  3. secretion into bile

similar to Dubin-Johnson syndrome

liver cells not pigmented

increased conjugated bilirubin in blood
- can have increase in BOTH conjugated and unconjugated bilirubin

Gene mutation OATP1B1 and OATP1B3

Enterohepatic recycling of bilirubin is compromised

44
Q

Gallstones

  • nickname
  • causes (4)
  • storage of gallstone
A

aka cholelithiasis

Causes:

  1. too much absorption of water from bile
  2. too much absorption of bile acids from bile
  3. too much cholesterol in bile
  4. inflammation f epithelium

Storage:
75%- gallstones stay in gallbladder
20%- cystic duct ( biliary pain)

45
Q

LFT: abnormal bilirubin

A

tests liver’s ability to detoxify metabolites and transport organic anions into bile

exm. hyperbilirubinemia
- figure out whether predominantly conjugated or unconjugated

46
Q

LFT: abnormal albumin

A

severe impairment in liver function reduces albumin

  • can occur in heart failrue, nephrotic syndrome, protein losing enteropathy, and/or malnutrition
47
Q

LFT: abnormal prothrombin time

A

reflects degree of liver failure
- PT increase as ability of liver failure/hepatic dysfunction diminishes

  • correlates with liver failure/hepatic dysfunction

INR- international normalized ratio

GI Final (15 decks)

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