Liver Physiology and Function Flashcards

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1
Q

What are the main aspects of structure which can affect the function of the live?

A
  • Vascular System
  • Biliary Tree
  • 3D arrangement of liver cells.
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2
Q

In terms of blood supply, where is 75% of the blood supply coming in from?

A

The portal vein = this is ALL venous blood and is the blood which is returning from the GI tract.
GI TRACT = (spleen / pancreas / small intestine.)

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3
Q

In terms of blood supply, where is 25% of the blood supply coming in from?

A

The hepatic artery = this is ALL oxygenated blood.

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4
Q

Where does the portal vein feed into?

A

Portal vein feeds into the liver.

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5
Q

Where does the hepatic vein take blood to?

A

Takes blood back to the vena cava.

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6
Q

Where does blood from the central vein in the liver lobules drain into and what is the following step from this?

A

Drains into the hepatic vein and then, travels straight into the vena cava.

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7
Q

Where does the portal vein bring blood from?

A

Carries blood returning from the gastrointestinal tract.

NUTRIENT RICH BLOOD.

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8
Q

What does the gastrointestinal tract consist of?

A

Passes the gallbladder -> pancreas -> spleen -> liver.

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9
Q

What illness is associated with the portal vein?

A

Portal Hypertension = Increase in blood pressure.

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10
Q

In terms of histological organisation of the liver, what are the 4 main parts?

A

Parenchyma
Stroma
Bile Duct
Hepatic Artery

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11
Q

What is the parenchyma?

A

It is represented by the hepatocytes.

It is functional tissue of an organ.

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12
Q

What is the stroma?

A

Connective tissue of the stroma forms a MESHWORK.

This provides integrity for the hepatocytes and the sinusoids.

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13
Q

What is the bile duct?

A

This is where the bile duct is made in the cells and thus, allows the bile to be transported.

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14
Q

What is the hepatic artery?

A

This is the artery in which ALL the blood is oxygenated.

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15
Q

What. makes up the portal triad?

A

Bile duct
Portal vein
Hepatic Artery

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16
Q

Which two veins are found at the centre of the hepatic lobules?

A

Central Vein

Hepatic Vein

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17
Q

What is the difference between the blood entering the lobule and the blood leaving the lobule?

A

The blood entering the lobule is OXYGEN RICH but the blood leaving the lobule is OXYGEN POOR.

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18
Q

What is the main process which occurs in the hepatic lobule?

A

The blood enters the lobules via the branches of the portal vein and the hepatic artery.
Flows through the sinusoids.
Once the hepatocytes have cleared the blood, they exit the lobule via the central vein.

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19
Q

What is the purpose of the hepatocytes?

A

These remove toxic substances.

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20
Q

What are the 4 basic cells found in the liver?

A

Kupffer Cell
Liver Endothelial Cell
Stellate Fat Storing Cell
Hepatocytes Cell

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21
Q

What is the purpose of the Kupffer cells?

A

These cells line the sinusoids.

They have phagocytic activity which REMOVE aged / damaged RBC’s / viruses / immune complexes.

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22
Q

What is the purpose of the Stellate fat storing cells?

A

These store the majority of vitamin A.

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23
Q

What is the purpose of the liver endothelial cells?

A

These form a FENESTRA which allows efficient flow.

These can absorb solutes from the plasma and secrete material into it.

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24
Q

What is the purpose of the hepatocytes?

A

These perform MOST metabolic functions.

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25
Q

What is the percentage of hepatocytes compared to Kupffer cells?

A

Hepatocytes = 60%

Kupffer Cells = 30%

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26
Q

Due to whose function does less than 1% of macrophages enter the systemic circulation?

A

Kupffer Cells.

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27
Q

What is the purpose of sinusoids?

A

These have LARGE openings which allows the passage of solutes.

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28
Q

What is the biliary system?

A

These are organs and ducts which make / store bile.

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29
Q

What is bile?

A

Fluids made in the liver which help DIGEST fat.

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30
Q

Name the key parts of the biliary system.

A
Bile secreted by hepatocytes. 
Travels through: 
- Cananlinculi
- Ductules
- Hepatic Ducts 
- Common Bile Duct
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31
Q

How does the surface area of the biliary system aid the function?

A

There is a massive surface area which allows for the exchange of molecules.

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32
Q

What are the two main components of bile?

A

Cholic Acid

Chenodeoxycholic Acid

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33
Q

Where is bile secreted from and into where?

A

Secreted by the hepatocytes and secreted into the duodenum.

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34
Q

Where is bile usually stored in?

A

Stored in the gallbladder.

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35
Q

How are bile salts formed?

A

This is when cholic acid and chenodeoxycholic acid are conjugated with GLYCINE and TAURINE.

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36
Q

What is the purpose of the spinchter of odii?

A

Entry of bile into the duodenum is controlled by the sphincter.
It is a smooth muscle.

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37
Q

What are the 2 main functions of bile?

A

Digests fat and absorbs fat too.

Eliminates waste products.

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38
Q

What are the 2 waste products produced by bile?

A

Bilirubin

Cholesterol

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39
Q

What is bilirubin?

A

It is a yellow pigment which has been formed from the breakdown of haemoglobin.

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40
Q

How is bilirubin excreted and eliminated from the body?

A

It is excreted from the body by secretion into bile and then, is eliminated into the faeces.

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41
Q

What is Cholecystokinin?

It is also known as CCK.

A

This is a peptide hormone which causes the contraction of the gallbladder.
This contraction leads to the ejection of bile into the duodenum.

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42
Q

What does CCK aid with?

A

It facilitates digestion within the small intestine.

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43
Q

Where is CCK secreted from?

A

It is secreted from the mucosal epithelial cells.

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44
Q

What is enterohepatic circulation of bile?

A

This is the circulation of biliary acids / bilirubin / drugs from LIVER TO BILE.
This enters the small intestine and is absorbed by the enterocyte.
From the enterocyte, it’s transported back to the liver.

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45
Q

Which part of the small intestine does it enter?

A

It enters the interstitial lumen.

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46
Q

What is another name for enterohepatic circulation of bile?

A

This is also known as ‘Portal Circulation’.

47
Q

What is a short summary of what enterohepatic circulation entails?

A

Blood flows from abdominal organs that passes through the portal vein / sinusoids / hepatic vein / vena cava.

48
Q

What is plasma protein synthesis?

A

Hepatocytes synthesis and release MOST of the plasma proteins.

49
Q

What are the 3 blood clotting factors?

A

Fibrinogn
Prothrombin
Nearly ALL other factors ( eg: V / VI / IX / X /XII )

50
Q

What is vitamin K essential for?

A

It is essential for the formation of prothrombin and clotting factors: II / VII / IX / X

51
Q

What happens if the vitamin K levels are lacking?

A

If lacking in levels, it can lead to MAJOR homeostasis.

52
Q

What can a lack of clotting factors lead to?

A

This can lead to excessive bleeding.

53
Q

What is the vitamin K enzyme associated with the production of coagulation factors?

A

Vitamin K Epoxide Reductase.

54
Q

How does warfarin contribute to the vitamin K scenario?

A

Warfarin INHIBITS this enzyme and thus reduces the synthesis of coagulation factors.

55
Q

What can issues with the liver lead to regarding vitamins?

A

It can lead to vitamin and iron deficiency.

56
Q

Which vitamins are fat - soluble?

A

Vitamins A / D / E / K

57
Q

Where are fat - soluble vitamins stored?

A

These can be stored in the liver or fat tissues.

58
Q

In terms of carbohydrates, what is it metabolised into?

A

Glucagon

Insulin

59
Q

What happens to the lipids, when the lipid level is TOO HIGH?

A

These lipids are put into storage.

60
Q

What happens to the lipids when the lipid level is TOO low?

A

The liver cells break down fats and thus produce energy.

61
Q

In terms of proteins, what are the 2 processes which occur?

A

Gluconeogenesis

Deamination

62
Q

What does gluconeogenesis involve?

A

The liver removes EXCESS amino acids from the bloodstream and thus it can be converted into glucose.

63
Q

What does deamination involve?

A

Process by which amino acids are broken down in order to produce energy.
This forms ammonia.

64
Q

How is the ammonia produced in deamination removed?

A

This is neutralised by the liver and then converted into urea.
This is excreted by the kidneys.

65
Q

Name the 3 sources of cholesterol.

A

Dietary Cholesterol
De Novo Synthesis in the liver
Cholesterol from extra hepatic tissue

66
Q

What does de novo mean?

A

Made in the liver.

67
Q

What is the purpose of HDL’s?

A

These transport cholesterol to the liver and thus his REMOVED from the bloodstream.

68
Q

How much of the cholesterol is made in the liver?

A

Around 50% of cholesterol is made in the body by the liver.

69
Q

Explain how glucose metabolism occurs?

A

Acetyl Co-A is converted into cholesterol.
Enzyme which works on this is HMG co - A reductase.
This is the target for Statins (which are cholesterol lowering drugs).

70
Q

What are lipoproteins?

A

These transport ALL hydrophobic fat molecules.

71
Q

Name some examples of lipoproteins.

A
Chylomicrons 
vLDL
LDL
IDL
HDL
72
Q

What are chylomicrons?

A

These are fat globules which are composed of protein and fat.
These are found in the blood and lymphatic fluids.

73
Q

How can you describe chylomicrons in terms of size?

A

These are the LARGEST yet the LEAST DENSE lipoproteins.

74
Q

In terms of cholesterol trafficking, list the procedure.

A

Cholesterol LEAVES the liver in vLDL’s.
These circulate around the body in the bloodstream.
Lipoproteins are broken off via the usage of the enzyme lipoprotein lipase.
Therefore, LDL’s are created.

75
Q

What does chylomicrons transport?

A

These transport dietary cholesterol.

76
Q

What are vLDL’s?

A

This is the way fatty acids are transported.

77
Q

What are LDL’s?

A

These transport cholesterol to the tissues.

This leads to FAT ACCUMULATION.

78
Q

What are HDL’s?

A

Liver is empty and therefore picks up EXCESS cholesterol in order to bring it back to the liver.

79
Q

Where is excess cholesterol excreted in?

A

Bile.

80
Q

Why is detoxification important?

A

The liver is vital for metabolism and excretion of various substances that could be toxic to the body.

81
Q

Name some substances which the liver detoxifies.

A

Bilirubin
Ammonia
Hormones
Drugs and Exogenous Toxins

82
Q

What are exogenous toxins?

A

These are present in the outside environment.

These are absorbed via eating // breathing.

83
Q

What are the 2 stages of detoxification?

A

Phase 1 = Oxidation / Reduction

Phase 2 = Conjugation

84
Q

Explain what occurs in Phase 1 in greater detail.

A

Oxidation occurs = Usage of cytochrome P - 450 enzymes.

This results in the substrate being MORE polar as it can sometimes be very TOXIC.

85
Q

Explain what occurs in Phase 1 in greater detail.

A

Oxidation occurs = Usage of cytochrome P - 450 enzymes.

This results in the substrate being MORE polar as it can sometimes be very TOXIC.

86
Q

Explain what occurs in Phase 2 in greater detail.

A

Conjugation Pathway occurs = This makes the drug MORE water soluble.
Therefore, it can be eliminated out of the body.

87
Q

What kinds of groups are present within the conjugation pathway?

A

Acetyl / Methyl / Glycl

88
Q

What is cytochrome P450?

A

This is a group of enzymes which are used in order to digest fats and bile acids.

89
Q

What are the 2 most important cytochrome p450 enzymes?

A

CYP1A

CYP2E

90
Q

Where are cytochrome p450 enzymes found?

A

These heme - containing group of enzymes are usually embedded in the lipid bilayer of the endoplasmic reticulum.

91
Q

What is another name for paracetamol?

A

Acetaminophen

92
Q

What kind of therapeutic index does paracetamol have?

A

A very narrow index.

93
Q

What is the maximum dosage for paracetamol?

A

4 grams per day or 1 gram per dose.

94
Q

What is the number of pathways paracetamol can take?

A

It can take 3 routes.

95
Q

What are the 3 routes paracetamol can take?

A

1) Gluthaione Conjugation (45 - 55%)
2) Sulfation (20 - 30%)
3) Hydroxylation by Cytochrome (15%)

96
Q

What happens when there is a paracetamol overdose?

A

Liver enzymes become SATURATED.

This leads to liver necrosis and then damage to the kidney by toxic metabolites.

97
Q

What is the substance whereby 90% of it is metabolised and oxidised in the liver?

A

Ethanol.

98
Q

What are the 2 main steps which occurs whereby ethanol is eliminated by the body?

A

1) Oxidation of ethanal to acetaldehyde = CATALYSED BY ALCOHOL DEHYDROGENASE.
2) Acetaldehyde is converted into acetate = CATALYSED BY ACETALDEHYDE DEHYDROGENASE.

99
Q

What occurs if the conversion to acetate DOES NOT occur?

A

Flushing of the skin.
Increase in heart rate.
There is severe hyperventilation.

100
Q

What are people prescribed in order to deal with the effects of no conversion to acetate?

A

Disulfiram.

101
Q

What is a condition which occurs in alcoholics where they have TOO many lipids?

A

Hyperlipemia : Increase in fatty acids which increases the fatty deposits in the arteries and also increases the risk of blockages.

102
Q

What are the 3 stages of alcohol induced liver damage?

A

Fatty Liver = Liver enlarges due to fatty deposits.
Liver Fibrosis = Scar tissue forms.
Cirrhosis = Growth of connective tissues leads to destruction of liver cells.

103
Q

What are the 3 conditions people can develop from liver problems?

A

Jaundice
Hepatitis
Cirrhosis

104
Q

Explain what jaundice is in greater detail.

A

This is when there are excessive amounts of bilirubin in extracellular fluid.

105
Q

What can cause jaundice?

A

Inflamed liver to obstructed bile duct.

106
Q

What are the 3 main ‘types’ of jaundice?

A

Pre - Hepatic
Hepatic
Post - Hepatic (Obstructive)

107
Q

What is pre - hepatic jaundice?

A

Excessive breakdown of RBC = this is known as neonatal jaundice.

108
Q

What is hepatic jaundice?

A

Hepatocyte damage.
This condition arises in cirrhosis / drugs / hepatitis A / B / C / E.
This is known as Gilberts Syndrome.

109
Q

What is post - hepatic jaundice?

A

This is obstruction to passage in duodenum.
This can enter the blood circulation and also into the urine.
This turns the urine VERY DARK.
This arises in gallstones / carcinoma of pancreas / bile ducts.

110
Q

What is hepatitis?

A

This is an inflammatory condition of the liver.

Stimulates from viral infection / alcohol / toxins / autoimmune diseases.

111
Q

What is the primary and secondary cause of hepatitis?

A
Primary = Viral Infection. 
Secondary = Alcohol / Toxins / Autoimmune.
112
Q

What is cirrhosis of the liver?

A

Scarring of the liver.

113
Q

What are the 3 main stages of cirrhosis?

A

Stage 1 = Fatty Liver.
Stage 2 = Alcoholic hepatitis = cells DIE due to inflammation.
Stage 3 = Cirrhosis : fibrosis / scarring / cell death.

114
Q

What are the 2 main complications which arise with cirrhosis?

A

GI bleeding / Encephalopathy.