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LSS Alimentary System > 4 Liver > Flashcards

4 Liver Flashcards

1
Q

Q: Where does the liver lie? protection? What is it connected to? function?

A

A: upper right quadrant of the abdomen (protected by ribcage)

gall bladder (stores bile from liver) and (when stimulated) squirts it into the duodenum

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2
Q

Q: What are the 3 overarching functions of the liver?

A

A: Metabolic and catabolic functions: synthesis and utilization of carbohydrates, lipids and proteins.

Secretory and excretory functions: synthesis and secretion of bile and waste products

Detoxification and immunological functions: breakdown of ingested pathogens and processing of drugs

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3
Q

Q: What are the 3 roles of bile? Produced by? Flow?

A

A: Emulsification and absorption of fat: to increase surface area for lipase activity

Cholesterol homeostasis: excreting excess as needed

Toxin excretion: endogenous (e.g. bilirubin) and exogenous (e.g. drugs)

  • produced by hepatocytes
  • flow along caniculus to bile duct (opposite direction to blood flow)
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4
Q

Q: How can the liver be separated in terms of lobes? Anterior. Posterior. Diagram.

A

A: -2 lobes (shape is a right angled triangle with right angle top left and long side at top)

  • right lobe (large part) | left lobe
  • separated by falciform ligament- connects it to diaphragm

left lobe | caudate lobe | left hepatic vein | hepatic artery proper | Quadrate lobe (IVA + HPV + common bile duct = hilus) | gall bladder | right lobe

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5
Q

Q: What is the liver blood supply in terms of richness? Dual? Drainage?

A

A: rich blood supply: 25% of resting cardiac output

dual blood supply: 20% arterial blood from hepatic artery (L and R branches)- from heart
80% venous blood draining from the gut through the hepatic portal vein

blood from the liver drains into the inferior vena cava via the hepatic vein

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6
Q

Q: How can the liver be separated in terms of segments Central? Peripheral? Drainage? Damage? Which segment is usually slip into subsegments?

A

A: discrete segments (8), with their own anatomical borders

  • centrally: portal vein, hepatic artery and bile duct
  • peripherally: hepatic vein (drainage)

subsequently hepatic veins drain into the left, middle and right hepatic veins before joining the vena cava

Because of this, it is quite possible to have severe damage in one part of the liver without affecting other parts

IV is usually split into upper (a) and lower (b) subsegments

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7
Q

Q: Draw a diagram showing how the liver segments are numbered? Include 4 veins.

A

A: numbered clockwise (from front view where right lobe is on left)

right hepatic vein, portal vein, middle hepatic vein, left hepatic vein

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8
Q

Q: What is a structural unit of liver tissue? shape? Diagram.

A

A: hepatic lobule- roughly hexagonal

each corner consists of a portal triad that links with 3 adjacent lobules

at the centre of each lobule is a central vein which collects blood draining from the hepatic sinusoids to return it to the systemic venous system via the hepatic veins

within the lobule are rows of hepatocytes with each hepatocyte having a sinusoid- facing side and a canaliculi- facing side

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9
Q

Q: What does the portal triad consist of?

A

A: 3 vessels/conduits

  • branch of hepatic portal vein: coming in with mixed venous blood directly from gastrointestinal organs and spleen
  • branch of hepatic artery: brings oxygen rich blood to help support hepatocyte activity (high energy demand)
  • bile duct: bile that is produced by hepatocytes drains into tiny canals called bile canlculi which eventually coalesce with the bile ducts located around the lobule perimeter
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10
Q

Q: What is the role of hepatocytes? (4) What supports activity? What do they synthesise?

A

A: -process nutrients

  • detoxify blood
  • excrete waste substances before the blood returns to circulation
  • drug metabolism

oxygen rich blood to help support hepatocyte activity (high energy demand)

  • albumin
  • clotting products/factors
  • bile salts
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11
Q

Q: Which cells are in the liver? (5) Diagram for arrangement.

A

A: -hepatocytes (80%)= large with pale and rounded nuclei

  • kupffer= fixed phagocytes=liver macrophages
  • cholangiocytes= bile duct epithelial cells
  • endothelial cells= line blood vessels and sinusoids
  • hepatic stellate cells= vitamin A storage-> can be activated to a fribrogenic myofibroblastic phenotype
bile canaliculi (no cilia on this side of hepatocytes)
hepatocytes
space of dissie
quiescent stellate cell (between hep and endo)
endothelial cells
kupffer
sinusoid 
endothelial again
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12
Q

Q: What’s the arrangement of hepatocytes? blood movement? Shape? What percentage of liver mass?

A

A: in lots of cords (sheets) radiating from central vein

diffuses down through sheets towards central vein

cuboidal

80%

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13
Q

Q: What is an hepatic acinus?

A

A: functional unit of liver tissue that is harder to define anatomically than a hepatic lobule
consists of 2 adjacent 1/6 lobules that share 2 portal triads and extend as far as central veins

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14
Q

Q: What is the 3 zone model? Refers to?

A

A: refers to hepatic acinus

due to the arrangement and the way blood is received from the hepatic portal vein and artery (the 2 1/6th lobules have in common) and drains into the outer parts of each 1/6th lobule being the hepatic vein

hepatocytes towards to the outside of the lobules receive ‘early exposure’ to blood contents which includes good components eg O2 and bad eg toxins

3 | 2 | 1 | 1 | 2 | 3

where 1 receives high oxygen and high toxins

3 receives low oxygen and low toxin risk

2 is medium for both

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15
Q

Q: What are hepatic sinusoids? Key features? (3) What occurs to blood as it passes through?

A

A: specialised capillaries different from systemic ones

  • wider than normal allowing slower blood flow
  • no basement membrane
  • have fenestrations- gaps between endothelial cells in wall= makes them leaky

-> leakage of plasma and plasma borne substances eg lipids from the vessel to enter extravascular space between sinusoids and liver cells-> this gap is the space of disse

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16
Q

Q: What are kupffer cells? Where? Shape? What percentage of liver cell population? Function? (3)

A

A: -sinusoidal macrophages (internal wall of sinusoids)

  • attached to endothelial cells
  • stellate shaped
  • 15% of liver cell population
  • eliminate and detoxify substances arriving into liver from portal circulation (inc phagocytosing)
  • these immunological cells also release cytokines that are able to activate hepatic stellate cells in the space of disse
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17
Q

Q: In what state do hepatic stellate cells exist? (2) Acts as? What can change this? New name? Characteristics following this? (3) Downside?

A

A: -dormant/quiescent and perisinusoidal

  • vitamin A storage in liver cytosolic droplets
  • become activated (now called fibroblasts) in response to liver damage/ activation by kupffer cells
  • proliferate, chemotactic and deposit collagen in extracellular matrix = fibrogenesis

can lead to cirrhosis since produced when under duress

18
Q

Q: What’s the role of cholangiocytes? where?

A

A: -secrete bicarbonate and water to form bile

-line bile duct

19
Q

Q: What are the 3 non parenchymal cells of the liver?

A

A: -kupffer

  • endothelial
  • hepatocytes
20
Q

Q: What are 6 metabolic functions of hepatocytes?

A

A: -carbohydrate metabolism

  • (glucose storage as glycogen)/ other storage
  • protein synthesis
  • protein metabolism
  • triglyceride metabolism
  • detoxification
21
Q

Q: What happens after a meal? Location? (2) How is it obtained again? 24hr fast?

A

A: after meal, blood glucose increases and is taken up by tissues

  • stored as glycogen mainly in muscle and liver
  • breakdown liver glycogen maintains blood glucose concentration between meals (muscle can’t release glucose back into blood)
  • 24hr fast will exhaust liver glycogen (80g)
22
Q

Q: Explain the process of carbohydrate metabolism in the liver. When does this process occur?

A

A: Cori cycle

  • muscle starts undergoing anaerobic respiration (fermentation)=> lactate/lactic acid= can be used to regenerate glucose
  • enter liver as pyruvate via lactate dehydrogenase
  • uses ATP to undergo gluconeogenesis=> get glucose
  • enters muscle cell-> used in glycolysis etc

when muscle runs out of its own energy stores

23
Q

Q: What do hepatocytes contain? (8)

A

A: -glycogen

  • lysozomes:
  • nucleus
  • GA
  • rER in abundance
  • mitochondria: lots of energy dependent processes
  • sER for carbohydrate and phospholipid synthesis
  • cytoplasmic enzymes
24
Q

Q: What’s the role of cytoplasmic enzymes in hepatocytes? (3)

A

A: support processes eg

  • deamination
  • glycogenolysis
  • gluconeogenesis
25
Q

Q: What do lysozomes do in hepatocytes? (4)

A

A: acidic organelle with roles in cell management and protein,lipid,carbo,nuclei acid breakdown

26
Q

Q: Outline how hepatocytes synthesise proteins? (3) 3 examples. By which process do you get different aa? for which aa?

A

A: 1. take aa from diet (when in fed state) and from muscle cells (in fasted state)

  1. aa enter liver
  2. turned into proteins

plasma proteins, clotting factors, lipoproteins

transamination- take aa and produce another (how non essential aa are made)

27
Q

Q: What can alpha ketoglutate be converted into? (2) pyruvate? oxaloacetate?

A

A: glutamate, proline, (arginine)
alanine, (valine, leucine)
asparate, (methionine, lysine)

28
Q

Q: What’s the problem with deamination in muscle? (2) Solution?

A

A: muscle can potentially utilise aa to produce glucose for energy BUT

  1. to convert pyruvate into glucose requires energy
  2. to remove nitrogen as urea requires energy

transfer problem to liver (glucose-alanine cycle)

29
Q

Q: Describe the glucose-alanine cycle? (4)

A

A: muscle cell: pyruvate (from glycolysis) + glutamate (from aa breakdown) -> alanine
liver cell: alanine undergoes transamination with alpha ketoglutarate -> glutamate + pyruvate

glutamate uses 4ATP (and is broken down) and makes urea which enters blood= excreted

pyruvate uses 6ATP to make glucose and that enters liver cell to undergo glycolysis

30
Q

Q: Describe tryglyceride metabolism. (4) Alternative?

A

A: 1. adipose tissue cell contains triglyceride-> metabolised -> FAs

  1. enter liver
  2. beta oxidation-> acetyl CoA= made as energy resource for itself
  3. TCA cycle

or

  1. 2 Acetyl CoA make acetoacetate (ketone body)-> used as energy source for other tissues eg brain and muscle-> can be excreted into blood
31
Q

Q: Describe lipoprotein synthesis in hepatocytes. (7)

A

A: 1. glucose enters liver

  1. glucose-> converted-> pyruvate and GLYCEROL
  2. pyruvate-> acetyl CoA
  3. acetyl CoA-> by malonyl CoA-> FATTY ACIDS
  4. acetyl CoA-> CHOLESTEROL

GLYCEROL and FA and CHOLESTEROL= major lipoprotein components

  1. GLYCEROL + FA -> triacyl glycerol
  2. triacyl glycerol + apoprotein phospholipids + cholesterol => lipoproteins
32
Q

Q: What happens to lipoproteins that hepatocytes synthesise? (4)

A

A: become

  • HDL= empty and go round picking up excess cholesterol
  • VLDL= transport FA to tissues
    • > become LDL= transport cholesterol to tissue
    • > become triacylglycerodes in adipose tissue
33
Q

Q: What do hepatocytes store? (5) Sufficient for?

A

A: -iron as ferritin available for erythropoesis

  • fat soluble vitamins eg A D E K
  • sufficient for 6-12 months but not K
  • K is essential to blood clotting
34
Q

Q: What do hepatocytes detoxify? Using? Process? Result? (2) Another method? downside?

A

A: chemicals and drugs

-P450 enzymes= 2 stage process
phase 1= makes them more hydrophilic
phase 2= attach to water soluble side chain to make them less reactive

-> makes them easy to excrete and less likely to cause damage to body

excrete them via bile (to avoid them going into circulation), and eventually the faeces. However they may get reabsorbed in the small intestine and re-enter the portal circulation cyclically, significantly increasing their half-life (enterohepatic circulation)

35
Q

Q: What does the biliary tree describe? Starts as? Then? (5) What’s this connected to? connects? Result? extends to? What else attaches? Now called? Where does to go?

A

A: describes the anatomical structures responsible for the transit and storage of bile

starts in millions of bile canaliculi adjacent to the hepatocytes (bile producing cells)
->canaliculi then drain into small ductules -> drain into small bile ducts -> coalesce into larger bile ducts for each liver segment

-> merge together to form the right and left hepatic ducts -> converge to form the common hepatic duct

Connected to this duct is the cystic duct, which connects the gall bladder (a small muscular storage organ) to the biliary tree

The merging of the common hepatic duct and the cystic duct forms the common bile duct, which extends towards the duodenum

pancreatic duct joins vessel -> now called ampulla of Vater
-> opens up into the medial wall of the duodenum at the duodenal papilla

36
Q

Q: What does bile contain? (5) Colour? why?

A

A: bile salts, bilirubin, drug metabolites, cholesterol + water = aq solution

yellow/green due to bilirubin (endogenous product)

37
Q

Q: Where is bile produced? (2- 3,6) When is it released? (2)

A

A: hepatocytes

  • 60% of total
  • primary secretion
  • reflects serum concentration of bile acids, lipids and organic ions

cholangiocytes

  • 40%: secondary modification
  • alters pH
  • water movement by osmosis
  • reabsorption of sugars and acids
  • secretion of HCO3- and Cl-
  • IgA exocytosed
  • constantly being synthesised and stored in gall bladder
  • CCK stimulates gall bladder contraction for a ‘big dose’
38
Q

Q: What are the functions of the gall bladder? (3)

A

A: -stores bile

  • acidifies bile (by absorbing HCO3-)
  • concentrates bile (by reabsorbing ions, creating osmotic gradient)
39
Q

Q: What is enterohepatic circulation? (7)

A

A: -cholesterol=> BS in liver

  • enter gal bladder and exit same way
  • BS enter common bile duct
  • bile salts enter end of duodenum via common bile duct
  • BS travel through ileum
  • exit at end of ileum and enter hepatic portal vein
  • BS enter liver (reabsorbed)
40
Q

Q: How can the enterohepatic circulation be a beneficial process? Result? (2)

A

A: for example in the recycling of bile salts (sometimes so efficiently that the same salts can be used twice to digest the same meal).

This improves the digestion and absorption of fats.

LSS Alimentary System (17 decks)

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