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Liver physiology Flashcards

1
Q

What are the main types of cells in the liver?

A

Hepatocytes, Kupffer cells, endothelial cells, stellate (Ito) cells

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2
Q

What is the function of the stellate cells and where are they located?

A

Perisinusoidal cells, located specifically in the Space of Disse.
Functions: store vitamin A, fat and collagen

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3
Q

What is the functional unit of the liver?

A

The hepatic lobule: hexagonal plates around a central hepatic portal vein

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4
Q

What does a portal triad contain?

A

Portal vein, hepatic artery, bile duct

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5
Q

What are Kupffer cells?

A

fixed tissue macrophages, which filter blood coming from the small intestine via the hepatic portal vein

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6
Q

In which direction does bile flow in the liver? In what?

A

Bile flows in canniculae (sit between hepatocytes). Flows in a retrograde manner from the common vein to the portal triad.

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7
Q

What are the main components of bile?

A

cholesterol, phospholipids, bilirubin, bile acids, water, electrolytes

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8
Q

What do hepatocytes do in bile secretion?

A

secrete bile acids, cholesterol and other organic components into the cannaliculae

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9
Q

What is the second stage of bile acid secretion facilitated by endothelial cells in bile ducts?

A

Addition of water to the bile salts etc, plus electrolytes (inc: Na+ and HCO3-)

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10
Q

What is the hormonal control of bile acid synthesis and release from the liver?

A

Secretin is released from S cells in response to gastric acid in the duodenum

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11
Q

How much bile does the gall bladder store on average?

A

30-50ml

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12
Q

What is the hormonal control for release of bile from the gall bladder?

A

Release of cholecystokinin (CCK) from I cells in response to fat in the duodenum.

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13
Q

Cholesterol is immediately broken into which 2 acids?

A

cholic acid + chenodeoxycholic acid

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14
Q

Why are bile salts conjugated with amino acids (e.g. taurine or glycine)?

A

AA-conjugation makes the bile salts water-soluble

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15
Q

What are primary bile salts?

A

Refers to the species occurring as Na+-salts, secreted from the liver

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16
Q

What are secondary bile salts?

A

Formation of deoxycholic acid and Lithocholic acid following bacterial fermentation in the small intestine

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17
Q

How are secondary bile salts transported back to the liver?

A

Transported from the terminal ileum via enterohepatic circulation back to the liver

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18
Q

What are 2 main types of gall stones?

A

Cholesterol (80%), pigment (20%)

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19
Q

What are the main risk factors for gall stones?

A

HFD, gall bladder mucosal inflammation, F>M, excess oestrogen

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20
Q

What is the function of bile?

A

To emulsify fats, enabling lipase-mediated digestion and aiding absorption

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21
Q

What is bilirubin?

A

Breakdown product of RBC degradation, yellow pigment

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22
Q

What helps to neutralise the HCL in gastric acid?

A

Bile + pancreatic juices

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23
Q

What reaction is bilirubin generated from?

A

Haem -> (iron +) porphyrin -> bilirubin

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24
Q

What is the intermediate formed before bilirubin that can cause a greenish jaundice

A

biliverdin

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25
Which cell type catalyses the breakdown of haem into bilirubin? Where does this occur?
Kupffer cells (macrophages) in the sinusoids of lobules
26
How is unconjugated bilirubin carried in the blood (during physiology)?
It is conjugated to albumin, thus making it water-soluble?
27
What are the 3 methods of paracetamol conjugation in the liver?
Sulfonation, n-hydroxylation, glucoronidation
28
What is free bilirubin conjugated to in the liver?
Glucuronic acid
29
How is conjugated bilirubin then excreted?
It leaves the liver with bile, and is then either excreted renally (as urobilin) or in faeces (as stercobilin)
30
What is jaundice? Why does it happen?
yellowish tinge to skin, mucosa or sclera (eyes). | Caused by accumulation of unconjugated/free bilirubin in the plasma
31
At what [bilirubin] is jaundice likely to be present?
>1.5mg/dL
32
How does conjugated bilirubin in the bile get excreted in faeces?
conjugated bilirubin is metabolised by intestinal microbiota, redox reactions promote the formation of stercobilin. This colours and is excreted in faeces
33
A mutation in what causes the rare green jaundice (biliverdin)? What can exacerbate this?
mutation in biliverdin reductase prevents conversion of biliverdin to bilirubin Can be aggravated by EtOH cirrhosis
34
What can be used to treat jaundice in low-income countries, particularly in infants? How do they work?
Sunlight canopies Filters so that only blue light gets through Therefore reduced UV-mediated damage
35
What are the 2 main processes by which glucose is generated in the liver?
gluconeogenesis | glycogenolysis
36
Through which process is Glucose-6-phosphate converted to pyruvate?
Glycolysis
37
Which enzyme catalyses the breakdown of glycogen to glu-1-P? | What is the name of this reaction?
Glycogen phosphorylase | Glycogenolysis
38
Which transporter is used for uptake of Glu into the hepatocyte?
Glut2
39
Which hormones stimulate glycogenolysis?
Glucagon (GCG) | Adrenaline
40
Which hormones stimulate glycogenesis?
insulin
41
What are the 4 methods of fat metabolism in the liver?
Adipose storage Oxidation of TGs to ATP (OXPHOS) Lipoprotein synthesis cholesterol and phospholipid synthesis
42
What are the 4 methods of protein metabolism in the liver?
transamination/deamination of AAs synthesis of non-essential AAs synthesis of plasma proteins (e.g. albumin) urea synthesis (excretion of ammonia)
43
How is glutamine (AA) removed by the liver?
Conversion to NH3 and then excretion via the urea cycle
44
Why is glutamine (accumulation) toxic?
Glutamine interferes with GABA and dopamine receptors and can cause hepatic encephalopathy
45
What clinical feature is indicative of excess/toxic oestrogen? How many is considered to be concerning?
Spider angiomas | >5
46
What are the broad phases of liver metabolism/detoxification? What do they involve?
``` Phase 1 (redox) Phase 2 (conjugation) Phase 3 (excretion) ```
47
Why is an OD more likely with paracetamol?
It has a narrow therapeutic window
48
What is the toxic metabolite generated through breakdown of paracetamol? Through which phase I reaction does it occur?
NAPQI | Generated through n-hydroxylation and dehydration of paracetetamol
49
What are the toxic effects of NAPQI?
Liver necrosis and renal failure
50
Why is there an accumulation of NAPQI in paracetamol during OD?
NAPQI should be conjugated to GSH, but this gets depleted and it is then left to circulate a free species in the plasma
51
What is the antidote for paracetamol OD? How does it work?
N-acetyl cysteine (NAC), IV infusion NAC is the precursor to GSH, it enables restoration of the GSH stores and therefore allows conjugation and excretion of NAPQI
52
How is EtOH metabolised?
EtOH -> acetaldehyde -> conjugate acid
53
Which enzymes catalyse the metabolism of EtoH?
``` alcohol dehydrogenase (EtOH -> acetylaldehyde) acetylaldehyde dehydrogenase (-> conjugate acid) ```
54
Consequences of chronic EtOH abuse (>10yr)
fatty liver disease cirrhosis alcoholic hepatitis
55
What kind of cells are hepatocytes?
stable cells: will only regenerate in response to injury or trauma. Otherwise cells are quiescent (G0)
56
What is an example of a labile cell?
Skin
57
What are the 2 main pathways of liver generation?
growth factor mediated | cytokine dependent
58
How does chronic EtOH dependence affect liver regeneration?
reduced ability for liver to regenerate
59
Activation of liver regeneration can occur via non-parenchymal cells. Which cells are these?
stellate (Ito) | Kupffer
60
Which LFT is an indicator of bile flow obstruction? Which other marker may be indicated?
elevated ALP | elevated GGT
61
Hypoalbuminaemia indicates:
malnutrition or chronic liver disease

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