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Alimentary system > 2. Liver > Flashcards

2. Liver Flashcards

1
Q

Location of the liver

A

Liver is very large

Mainly occupies upper right quadrant

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2
Q

Name the 4 lobes of the liver

A

Left
Right
Caudate
Quadrate

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3
Q

Which ligament attaches the liver to the diaphragm?

A

Falciform ligament

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4
Q

Which ligament connects the umbilicus of the anterior abdominal wall with the left branch of the hepatic portal vein?

A

Ligamentum teres

Round ligament

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5
Q

Which lobe of the liver is biggest?

A

Right lobe

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6
Q

Relative to the left and right lobes of the liver, where are the caudate and quadrate lobes found?

A

Caudate: Inbetween left and right
Quadrate: At the bottom between left and right

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7
Q

What is Calot’s triangle?

A

Triangular space that is dissected in a cholecystectomy to identify a window to safely expose the gallbladder.
Bound by: cystic duct, bile duct and the cystic artery

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8
Q

How is blood supply to the liver unique?

A

Has 2 supplies
Hepatic artery
Hepatic portal vein

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9
Q

Where does blood leave the liver?

A

Via the hepatic vein into IVC

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10
Q

Describe the Couinaud classification of the liver segments.

A

8 functionally independent segments: starting with 1 centrally and then going clockwise.
Each segment contains its own blood supply and drainage system.
Each segment can be resected without damaging the remaining segments.

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11
Q

How much of the resting cardiac output is required by the liver?

A

25%

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12
Q

Describe the proportions constituting the dual blood supply entering the liver

A

20% arterial blood from the hepatic artery (left and right branches)
80% venous blood draining from the gut through the hepatic portal vein

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13
Q

What is the purpose of blood delivered to the liver by the hepatic portal vein?

A

Takes absorbed breakdown products from the gut to the liver
Liver has huge metabolic role
Nothing absorbed from gut enters systemic circulation until its passes through the liver

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14
Q

What is the purpose of blood delivered to the liver by the hepatic artery?

A

Oxygenated, nutrient rich blood

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15
Q

What happens to the blood when it mixes from the hepatic portal vein and hepatic artery?

A

Combine into sinusoid

Blood becomes poorly oxygenated as so much (80%) is from hepatic venous supply

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16
Q

Describe the morphological divisions of the liver.

A

Divided into lobules and portal tracts/triads

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17
Q

Describe the functional divisions of the liver.

A

Acini
Blood flow
Bile flow

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18
Q

What is a lobule?

A

An area of the liver at a HISTOLOGICAL scale.
Hexagonal, with a portal triad at each corner
Divided in concentric centrilobular, midzonal and periportal parts

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19
Q

What does the portal triad consist of?

A

Branch of the hepatic portal vein
Branch of the hepatic artery
Bile duct

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20
Q

Describe the path of the blood flow through a lobule.

A

Blood flows towards the central vein

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21
Q

What is that shape of an acinus and what are its three regions?

A

Diamond
Periportal
Transition zone
Pericentral

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22
Q

Describe the direction of flow of bile in a liver lobule

A

Towards periphery

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23
Q

What are the 6 main roles of the liver?

A 
Metabolism
Digestion
Biosynthesis
Degradation
Detoxification
Storage
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24
Q

Name 5 cell types in the liver

A

Hepatocytes: 80% liver mass
Endothelial cells: lining blood vessels and sinusoids
Cholangiocytes: bile duct epithelial cells
Kupffer cells: Liver macrophages
Hepatic stellate cells: Vitamin A storage, may be activated to a fibrogenic myofibroblastic phenotype

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25
Q

What may flattened, dense cell nuclei that appear to be in the sinusoids be?

A

Kupffer cells

Hepatic stellate cells

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26
Q

Appearance of hepatocytes

A

Large cells

Pale and rounded nucleus

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27
Q

Where is the space of disse? What is found here?

A

Between endothelial cell and hepatocyte

Stellate cells present here, quiescent, monitoring

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28
Q

Which is the most abundant cell in the liver?

A

Hepatocytes

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29
Q

Describe the organisation of hepatocytes

A

Coordinated in sheets, radiating from central vein to the corners of the hexagons
Spaces in-between them are sinusoids

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30
Q

Acinus

A

Functional unit of hepatocytes divided into zones dependent on proximity to arterial blood supply

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31
Q

What are the 3 zones in an acini?

A

Periportal
Transition zone
Pericentral

32
Q

Which zone in the acinus receives the most oxygenated blood and what are the consequences of this?

A

Periportal zone 1
It is least susceptible to ischaemic injury
It is most susceptible to viral hepatitis or hemosiderin deposition in hemachromatosis

33
Q

What is the periportal zone involved in?

A

Gluconeogenesis
Oxidation of fatty acids
Cholesterol synthesis.

34
Q

What is the pericentral zone involved in?

A

Glycolysis
Lipogenesis
P450 based drug detoxification

35
Q

Which zone is most susceptible to ischaemia?

A

Pericentral: Zone 3

As furthest from well oxygenated blood

36
Q

What is bile produced by? Where does it flow?

A

Bile produced by hepatocytes

Flows along canaliculus to bile duct

37
Q

What is the canaliculus?

A

Thin tubular space between hepatocytes

Allows transport of bile secreted by hepatocytes

38
Q

What is found in bile?

A

Breakdown products of RBCs

Breakdown products of cholesterol

39
Q

Describe the histological appearance of hepatocytes, kupffer and endothelial cells

A

Kupfer cells: mucous blue
Endothelal cells: flat
Hepatocytes: red, round nuclei

40
Q

Describe the role of hepatic stellate cells

A

Vitamin A storage

Activation = ECM production (fibrogenesis)

41
Q

Describe the pathological role of hepatic stellate cells

A

Respond to pro-inflammatory environments: may lay down excessive ECM and can promote fibrosis
Important in liver cirrhosis: lose healthy liver tissue, replacing it with non functional fibrotic tissue: liver cant function

42
Q

What specialised feature characterises sinusoidal endothelial cells? What does this allow?

A

Fenestrated

Allows lipid and other large molecule movement to and from hepatocytes

43
Q

Describe the role of kupffer cells

A

Phagocytosis (inc. RBC breakdown)

Secretion of cytokines that promote Hepatic Stellate Cell activation: proliferation, contraction and fibrogenesis

44
Q

What do kupffer cells do in a pro-inflammatory environment?

A

Secrete cytokines, cause change so stellate cells more likely to cause fibrosis

45
Q

When blood glucose increases after a meal what occurs?

A

Taken up by muscle and liver, stored as glycogen

46
Q

What maintains blood glucose between meals and how long does this last?

A

Breakdown of glycogen stores in the liver

Liver stores enough glycogen for 24 hours

47
Q

What happens when there is not enough oxygen to supply the demands for ATP?

A

Can take pyruvate from glycolysis to re-liberate glucose via lactate
Problem: Energy dependent reaction, so muscle passes this role to the liver
Lactate produced by muscle
Lactate sent to liver
Liver converts lactate to pyruvate (using LDH)
Gluconeogenesis generates glucose from pyruvate (6 ATP required)
Glucose sent to muscle

48
Q

What is associated with hitting the wall when running a marathon?

A

Loss of glycogen store

Need to switch metabolism to other substrates which is more complex and slower

49
Q

2 sources of amino acids

A 
Diet
Muscle breakdown (in fasted state)
50
Q

What does the liver do with amino acids?

A

Generates proteins e.g.plasma proteins, clotting factors

51
Q

Essential amino acids

A

From diet

52
Q

Non-essential amino acids

A

Must be generated by body

53
Q

How are non-essential amino acids generated?

A

Transamination reactions between AAs and Keto acids

54
Q

Give an example of formation of a non essential amino acid e.g. glutamate

A

Alanine can be delivered by diet
Enters liver, reacts with alpha ketoglutarate
Transamination allows formation of glutamate (AA) + pyruvate which can be shuttled into other metabolic processes

55
Q

What determines the amino acid produced in a transamination reaction?

A

The transaminase enzyme

56
Q

Muscle can potentially utilise AAs to produce glucose for energy but to convert pyruvate to glucose requires energy and to remove nitrogen as urea requires energy. What is the solution to this?

A

Transfer problem to the liver for deamination (glucose-alanine cycle)

57
Q

Describe the glucose alanine cycle

A

Pyruvate from glycolysis and glutamate from AA breakdown combine to form alanine (in muscle cells)
Alanine travels to the liver
Deamination of alanine using alpha-ketoglutarate produces pyruvate and glutamate

58
Q

How does the glucose alanine cycle produce glucose?

A

Remove amino group from glutamate (generates urea and alpha-ketoglutarate)
Pyruvate can be fed into TCA to generate glucose
Glucose can be cycled back to muscle cell to be used in glycolysis

59
Q

What and where is the main energy store in the body?

A

Fat (100X glycogen)

Stored in adipose tissue and liver

60
Q

What happens when glycogen stores are full?

A

Liver can convert excess glucose and amino acids to fat for storage

61
Q

How are fats used as an energy source?

A

Breakdown triglycerides to liberate fatty acids
Fatty acids sent to liver
B-oxidation uses fatty acids to generate Acetyl CoA
Acetyl CoA can enter TCA

62
Q

Describe the formation of ketones in the liver

A

Fatty aids converted via B oxidation to Acetyl CoA
2 Acetyl CoA combined to form acetoacetate
Ketones secreted into blood
Tissues can utilise ketones to liberate Acetyl CoA

63
Q

What do ketones act as?

A

Method of delivering acetyl CoA to tissues so it can be used in TCA

64
Q

Which components of lipoproteins can be produced by glucose entering the liver?

A

Glycerol
Fatty acids
Cholesterol

65
Q

What happens to glucose when it enters the liver? (in reference to lipoprotein synthesis)

A

Glucose directly converted to glycerol

Glucose via TCA, converted to acetyl CoA via pyruvate

66
Q

What can acetyl CoA produced from glucose in the liver be converted to? (in reference to lipoprotein synthesis)

A 
Cholesterol (via HMG CoA reductase) 
Fatty acids (via the intermediate malonyl CoA).
67
Q

What are the components of triglycerides?

A

Glycerol + Fatty acids

68
Q

What are the components of lipoproteins?

A

Apoproteins + cholesterol + TAGs

69
Q

Which 2 lipoproteins are produced by the liver?

A

VLDL: high TAG content
HDL: high protein, low fat content

70
Q

What is the role of VLDL?

A

Transport fatty acids to tissues

Can be used as an energy source or stored in adipose tissue as TAGs

71
Q

What is the role of HDL?

A

Pick up excess cholesterol in the circulation and return to the liver

72
Q

What happens when VLDL have delivered fatty acids to tissues?

A

They are converted to LDL which are very high in cholesterol.
LDL deliver cholesterol to tissues

73
Q

2 major roles of cholesterol

A

Hormone production

Maintain cell membrane integrity

74
Q

What happens to excess cholesterol?

A

Returned to liver

Excreted as bile

75
Q

Describe the storage function of the liver

A

Storage of fat soluble vitamins (A,D,E,K).
Stores sufficient 6-12 month except Vit K where store is small.
Vit K essential blood clotting
Storage of iron as ferritin. Available for erythropoeisis

76
Q

Describe detoxification (drug metabolism) in the liver

A

Toxic compound enters liver
Phase 1: P450 enzymes try to make it more hydrophilic so it is easier to excrete
Phase 2: Attach water soluble side chain to make it less reactive

Alimentary system (15 decks)

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