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physiology 2 > liver physiology > Flashcards

liver physiology Flashcards

1
Q

functions of the liver

A
  • filtration/storage of blood
  • metabolism pf CHO/fats/hormones/foreign chemicals/ammonia
  • bile formation and disposal of lipid soluble things
  • storage of vitamins and Fe
  • formation pf blood proteins
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2
Q

hepatic circulation

A

uses venous blood to metabolise products of digestion that come from the portal vein
blood is mostly deoxygenated

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3
Q

how does the liver get oxygen

A

also has an arterial supply
most - 80% - is nutrient rich blood
other 20% Is oxygen rich arterial blood

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4
Q

where does the blood from the liver go

A

to the vena cava

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5
Q

liver blood resistance

A

needs to be low pressure to allow diffusion
los resistance
liver provides limited resistance to blood flow

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6
Q

mixing arterial and venous blood

A

very different pressures

lots of fluid is produced - lots of lymph

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7
Q

resident macrophages of the liver

A

kupffer cells
modified resident macrophages
removal of >99% of GIt bacteria
involved in iron metabolism 0 accumulation of ferritin

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8
Q

flow control in the liver

A
  • NA vasoconstriction contracts venous and hepatic artery - fight or flight response, diverts blood away from the liver
  • no known vasodilator fibres
  • when the metabolism is high, liver produces adenosine which binds to receptors and vasodilator to increase flow
  • sinusoids can be isolated
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9
Q

NA vasoconstriction in the liver

A

contracts venous and hepatic artery

fight or flight response

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10
Q

countercurrent flow

A

of bile

goes in the opposite direction to blood flow

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11
Q

lymph

A

removes volume without moving nutrient

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12
Q

when there is too much plasma glucose

A

liver absorbs some through glucose channels

stored as glycogen - glycogenesis

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13
Q

when there is not enough plasma glucose

A

liver liberates some and puts it into the blood stream

break down glycogen by glycogenolysis

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14
Q

glucose-6-phosphatase

A

enables glycogen to go back too glucose

only present in the liver

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15
Q

without glucose-6-phosphatase

A

muscles can break down glycogen but only to glucose-6-phosphatase, not all the way to glucose

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16
Q

glucose-6-phosphate

A

doesn’t go through glucose transporters, trapped inside the cell and must be used in situ

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17
Q

gluconeogenesis

A

when glucose is made from fat (glycerol), some amino acids, lactate - via pyruvate

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18
Q

formation/interconversion of CHO intermediates

A

liver can convert between different types of monosaccharides
can be converted to glucose because it is he principle monosaccharide used throughout the body

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19
Q

beta oxidation

A

breakdown of FAs to acetyl CoA

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20
Q

acetyl CoA used to synthesis

A

fats and cholesterol

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21
Q

breakdown of cholesterol

A

not possible in the human body

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22
Q

uses of cholesterol

A

made into bile salts and excreted directly into bile and steroid hormones

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23
Q

cholesterol stored as

A

cholesterol esters

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24
Q

protein metabolism

A

deaminated

remove carbon skeleton and use as fuel

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25
transamination
conversion between non-essential amino acids
26
removal of ammonia
converted into urea which is dumped into plasma and excreted into the kidneys
27
use of amino acids
used to make new proteins | all plasma proteins are synthesised in the liver eg. transferrin, albumin, angiotensin
28
ammonia-urea metabolism
NH3 is neurotoxic and is very permeable and can pass the BBB | converted to urea - only occurs in the liver
29
sources of ammonia
liver, colon, kidney etc | mainly liver
30
where is ammonia converted into urea
only in the liver
31
what happens to urea
excreted into plasma most of it is excreted in the kidneys some of it enters the GI and diffuses across the plasma membrane where it is broken down by bugs or is reabsorbed
32
kupffer cells
macrophages | kill bugs
33
drug metabolism
gets rid of lipid soluble drugs
34
liver metabolising blood borne hormones
Vit D and A when acting as hormones all steroids insulin and glucagon
35
cytochrome P450
enzymes | metabolise steroids
36
storage of vits and mins
``` stores vit A 5-10 months supply vit B12 - 1 year supply vitamins D - 2-4 months vitamin K stores iron ```
37
iron is bound to _ in the liver
ferritin - globular protein
38
ferroxidase
Fe2+ > Fe3+ (safe storage)
39
ferroductase
Fe3+ > Fe2+ (soluble release)
40
ferric iron
oxidised form completely insoluble storage form
41
ferrous iron
reduced form | water soluble - useful for transport
42
liver iron sensing
stores/releases iron is a controlled fashion liver sense elevated plasma and releases hepcidin which switches off iron channels in the gut and in the liver (ferroportin)
43
bile
for emulsification and absorption emulsifies fats in chyme increases access to lipase facilitates uptake of digested fat products by intestinal epithelial cells
44
excretion of waste products from blood
bilirubin - Hb breakdown product | excess hydrophobic stuff - cholesterol, drugs, xenobiotics, toxins
45
HDL uptake by
SR-B1
46
BSEP
exports bile salts
47
once bile is exported
can be stores in the gallbladder or released
48
production of bile salts
expensive too produce - mostly reabsorbed
49
ASBT
apical sodium dependant bile salt transporter in the ileum scavenger - secondary active transport puts bile salt into the blood stream where it goes to the liver via the portal vein
50
haem disposal
Hb phagocytosed, split into global and haem ferrous reused by being picked up with ferritin and sent to the liver the rest of the Hb is toxic enzymes converted it to bilirubin haem-oxigenase and biliverdin reductase both located in the spleen
51
haem-oxygenase
ring cleavage and Fe-release
52
biliverdin reductase
reduces biliverdin to bilirubin
53
bilirubin is bound to _ in the plasma
albumin
54
once albumin-bound bilirubin enters the liver
transport proteins for the bilirubin - organic anion transport protein bilirubin enters the cell add glnucaronic acid to make bilirubin di-gluconeride and/or bilirubin gluconeride
55
why cant you dump bilirubin into bile
is will be reabsorbed into plasma
56
why conjugate the bilirubin
so it can't cross plasma membranes and be reabsorbed into plasma
57
how do you conjugate the bilirubin
by using glucuronyl transferase on smooth endoplasmic reticulum
58
multidrug-resistance protein -2
pumps conjugated bilirubin into canaliculus in order to secrete into bile
59
how is conjugated bilirubin secreted into bile
via multi-drug resistance-protein 2
60
what do bacteria do to the conjugated bilirubin
deconjufate and and metabolise it to form urobilinogen which can be reabsorbed and sent back to the liver again
61
bacteria turn conjugated bilirubin into
urobilinogen
62
what happens to absorbed urobilinogen
sent back to the liver to attempt to remove again, some also lost via kidneys
63
jaundice
yellow tinted issues from excess bilirubin which causes a yellow pigment which dissolves into fatty tissues and eyes and skin
64
jaundice cause by either
1. haemolytic - excessive RBC destruction/myolysis 2. hepatic - impaired uptake, disturbed processes - disturbed secretion, obstruction, obstructive jaundice
65
assay of plasma of someone with haemolytic jaundice
excess free bilirubin
66
assay plasma of someone with hepatic jaundice caused by impaired uptake
excess free bilirubin
67
assay of plasma of someone with hepatic jaundice caused by disturbed secretion, obstruction - Obstructive Jaundice
excess free conjugated bilirubin
68
jaundice of the neonate
newborn infants have poorly developed bilirubin conjugation enzymes and jaundice is common - premature infants more affected
69
infants more commonly affected by jaundice
premature infants
70
problems with infants with jaundice
unconjugated bilirubin in the brain causes permanent damage
71
what is it called when there is unconjugated bilirubin in the brain causing damage
kernicterus - eten fatal
72
how to prevent brain damage in neonates
phototherapy | blue light converts the bilirubin to a photo isomer which is water soluble and can be excreted in the kidneys

physiology 2 (21 decks)

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