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vet 405: gi > Liver Physiology > Flashcards

Liver Physiology Flashcards

1
Q

what are the 5 main functions of the liver

A
  1. metabolism
  2. detoxification
  3. excretion
  4. storage
  5. synthesis
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2
Q

metabolism function of the liver

A
  • process nutrients, drugs, and bacteria
  • site of first pass metabolism
  • site of gluconeogenesis, fatty acid oxidation, deamination of amino acids
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3
Q

detoxification function of the liver

A
  • limits entry of toxic substances into the bloodstream
  • extracts toxins from elsewhere in the body and converts them into excrete-able forms
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4
Q

what is the main blood supply to the liver

A

venous (portal vein)

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5
Q

what does the liver store

A

glycogen
vitamins (B12, D, A)
copper
iron

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6
Q

lobes of the liver

A
  1. caudate
  2. right lateral
  3. right medial
  4. quadrate
  5. left medial
  6. left lateral
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7
Q

where is the gallbladder located

A

in between the right medial and quadrate lobes

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8
Q

liver lobules

A

hexagonally shaped functional units of the liver

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9
Q

hepatic triad

A

hepatic artery
portal vein
bile duct

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10
Q

where is the central vein located

A

in the center of the lobule

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11
Q

what direction do sinusoids run

A

from hepatic triad to central vein (outside –> inside of lobule)

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12
Q

what direction do bile canaliculi run

A

from center of lobule –> bile ductules (inside –> outside of lobule)

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13
Q

hepatocytes

A

polarized epithelial cells with a strong ability to regenerate

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14
Q

polarization of hepatocytes

A

apical: (sides) forms the bile canaliuli

basal: (top/bottom) contacts the sinusoids to detoxify blood as it passes through

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15
Q

zone 1

A

periportal zone
located around the hepatic triad (outside of lobule)

receives the highest concentration of oxygen, insulin, glucagon, and amino acids

function: gluconeogenesis, protein synthesis, lipid metabolism, urea cycle

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16
Q

zone 3

A

centrilobular zone
located around the central vein (inside of lobule)

receives the lowest concentration of oxygen and nutrients

function: CYP450 metabolism, glycolysis, lipogenesis, detoxification

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17
Q

what two mechanisms does the liver use to detoxify

A
  1. kupffer cells
  2. hepatocytes
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18
Q

kupffer cells

A

resident macrophages; phagocytic cells that line the sinusoids of the liver and are involved in RBC breakdown

  • detect foreign material in sinusoids
  • sample for immune responses (presents to T cells w/ MHC II)
  • clear gut-derived toxins
  • secrete pro-inflammatory cytokines
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19
Q

hepatocyte detox function

A

contain metabolic enzymes that solubilize toxins

site of phase 1 and 2 reactions

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20
Q

hepatocyte detox function

A

contain metabolic enzymes that solubilize toxins

site of phase 1 and 2 reactions

products get excreted into:
- bile –> feces
- bloodstream –> kidneys –> urine

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21
Q

phase 1 reaction

A

CYP450 reactions

oxidation, hydroxylation, etc

22
Q

phase 2 reactions

A

conjugation with another molecule

23
Q

bile

A

fluid produced by hepatocytes and stored in the gallbladder

24
Q

how do hepatocytes produce bile

A

hepatocytes break down cholesterol –> bile acids

secrete conjugated bilirubin, bile salts, cholesterol, phospholipids, proteins, ions, and water into canaliculi

25
Q

functions of bile

A
  1. emulsifies ingested fats
  2. neutralizes pH of duodenum
  3. forms micelles around fat
26
Q

micelles

A

bile acids (which have 1 hydrophilic and 1 hydrophobic side) that aggregate around droplets of fat

function: increases the surface area for the action of pancreatic lipase to allow fat to diffuse through epithelial cells in jejunum

27
Q

what is the flow of bile

A

canaliculi –> biliary ductule –> bile duct –> left/right hepatic duct –> common hepatic duct

28
Q

cholangiocytes

A

columnar epithelial cells that line biliary ductules and modify bile composition as it flows through
- contains mucous glands
- secretes IgA and IgM

29
Q

bile acids

A

produced by hepatocytes from cholesterol and modified by colonic bacteria

function: emulsifies fats for digestion

30
Q

primary bile acids

A

produced by hepatocytes

31
Q

secondary bile acids

A

modified by colonic bacteria

32
Q

enterohepatic circulation

A

unconjugated bile acids get reabsorbed from the intestines via the portal vein –> travels back to the liver –> recycled

conjugated bile acids can be deconjugated by microbiota and reabsorbed OR absorbed in ileum by ABST (apical sodium dependent bile acid transporter)

exception: 5% of conjugated bile acids (gets excreted in feces)

33
Q

bile stim tests

A

measures serum bile acids

supply 1 sample fasted and 1 sample fed to measure how well bile is produced and freely moving through biliary system

34
Q

bilirubin

A

metabolite of heme breakdown; provides color to bile, feces, and urine
- can be toxic in excess –> must be excreted
- insoluble - circulates bound to albumin and taken up by hepatocytes in sinusoids

35
Q

how is bilirubin excreted

A

hepatocytes take up bilirubin as it passes through sinusoids and conjugates it with glucaronic acid –> gets secreted in bile –> unable to undergo enterohepatic circulation –> excreted in feces

36
Q

gallbladder

A

muscular sac (diverticulum of the liver) used to concentrate and store bile

37
Q

what prevents the gallbladder from leaking

A

extremely resistance tight junctions between epithelial cells

38
Q

how does the gallbladder concentrate bile

A

absorbs Na+ from bile and exchanges for H+ –> draws water out of bile and into gallbladder cells –> concentrates bile –> empties into lumen of small intestine

39
Q

what controls bile release into small intestine

A
  1. CCK
  2. neural stimulation
40
Q

cholecystokinin

A

CCK; released by the SI in response to food entering; causes contraction of the gallbladder to release bile into common bile duct –> enters the intestines

41
Q

neural stimulation of the gallbladder

A

parasympathetic vagal afferents stimulate release of bile from gallbladder via vagal efferents

42
Q

cholestasis

A

obstruction of the biliary system:
1. choleliths
2. mucocele
3. cholecystitis

43
Q

choleliths

A

gallstones; concentrations of bile that form in the biliary system and prevent outflow of bile from the gallbladder

44
Q

mucocele

A

overproduction or dehydration of mucous from mucous glands in the gallbladder; causes a buildup of mucus that forms a mucus plus –> gallbladder inflammation

45
Q

cholecystitis

A

inflammation of the gallbladder; often results from obstruction

46
Q

jaundice/icterus

A

yellow discoloration of tissues by excess bile pigments (bilirubin)
- hyperbilirubinemia

47
Q

causes of jaundice/icterus

A
  1. pre-hepatic: overproduction of bilirubin from hemolysis
  2. hepatic: liver disease (cirrhosis, hepatitis) –> failure of hepatocytes to take up/conjugate bilirubin; impaired bilirubin transport
  3. post-hepatic: cholestasis, gallstones, tumors –> impaired uptake of transport, obstruction of bile flow
48
Q

causes of copper accumulation

A
  1. chronic copper poisoning
  2. hereditary copper toxicosis
  3. chronic hepatitis
49
Q

chronic copper poisoning

A

occurs in ruminants
- unable to regulate copper storage well
- too much Cu –> hepatocytes leak –> sudden release of Cu –> massive hemolysis

causes pigmentary nephropathy from hemoglobin

50
Q

hereditary copper toxicosis

A

mutation causing disruptions to normal excretion of Cu in bile leads to ongoing hepatocyte destruction
- certain breeds predisposed

51
Q

chronic hepatitis

A

chronic inflammation in liver affects normal excretion of bile leading to accumulation of copper

vet 405: gi (19 decks)

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