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Alimentary System > Liver > Flashcards

Liver Flashcards

1
Q

3 functions of the liver.

A
  1. Metabolic and catabolic functions
  2. Secretory and excretory functions
  3. Detoxification and immunological functions
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2
Q

Bile is secreted by hepatocytes. Functions of bile?

A
  1. Fat emulsification
  2. Cholesterol homeostasis
  3. Toxin excretion (endogenous) and exogenous
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3
Q

What ligament separates the 2 lobes of the liver?

A

Falciform ligament

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4
Q

What is a hepatic lobule?

BLOOD FLOWS TOWARDS CENTRE OF LOBULE, BILE FLOWS TOWARDS THE PERIMETER

A

Structural unit of liver tissue. Each corner of its hexagon contains a portal triad, linked with 3 adjacent lobules.

Rows of hepatocytes present within lobules. Each hepatocyte has a sinusoid facing side and a bile canaliculi facing side.

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5
Q

What is located at the centre of a liver lobule?

A

A central vein.

Vein collects blood from hepatic sinusoids - returns blood to systemic venous system via hepatic veins.

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6
Q

What are the components of the hepatic portal triad?

A
  1. Branch of hepatic portal vein - drains venous blood from gut containing toxins, bacteria, nutrients etc. It processes nutrients, detoxifies blood and excretes waste products.
  2. Hepatic artery - brings in oxygen rich blood into liver tissue. Helps support high energy demands of hepatocytes.
  3. Bile duct - bile produced by hepatocytes drains into bile canaliculi. These canaliculi coalesce with bile ducts in lobule perimeter (lined in cholagiocytes).
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7
Q

What is a hepatic acinus?

A

Functional unit of liver tissue.

Consists of 2 adjacent 1/6th lobules sharing 2 portal triads, extending as far as the central veins.

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8
Q

3 zone model of hepatic acinus

A

Eye of Agamotto. In to out.

Zone 1 - high O2, high toxin
Zone 2 - mid O2, mid toxin
Zone 3 - low O2, low toxin

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9
Q

Describe endothelial cells in the liver.

A

Discontinous - they are leaky. No basement membrane

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10
Q

Describe Kupfer cells

A

Sinusoidal macrophage - common. Only in liver. Phagocytose toxins and other bacteria in the blood. Also release cytokines to activate hepatic stellate cells in the space of Disse.

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11
Q

Describe hepatic stellate cells

A
  1. Quiescent
  2. Store Vitamin A in liver cytosolic droplets
  3. Activated in response to liver damage, were they proliferate and deposit collagen - can lead to fibrosis and cirrhosis.
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12
Q

Describe hepatocytes.

A
  1. 80% of liver mass.
  2. Cubical, synthesise things like Albumin, clotting products/factors, bile salts.
  3. Drug metabolism
  4. Receive nutrients, etc from sinusoid
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13
Q

Describe cholangiocytes.

A

Secrete bicarbonate and water - forming bile.

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14
Q

Aside from classic cell structures, what else do hepatocytes have?

A
  1. Glycogen

2. Peroxizomes (waste management, cholesterol/bile synthesis)

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15
Q

Explain how the biliary tree progresses.

A

Bile canaliculi - small ductules - larger bile ducts - Rt/Lt hepatic duct - common hepatic duct - cystic duct (connects gall bladder to biliary tree).

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16
Q

What forms the common bile duct?

A

Common hepatic duct and cystic duct.

Common bile duct goes to duodenum and is joined by the pancreatic duct - the vessel is called the ampulla of Vater.

The ampulla of Vater goes to medial wall of duodenum at duodenal papilla.

17
Q

What are the functions of bile? CAT

A
  1. Cholesterol homeostasis
  2. Absorption and digestion (ADEK)
  3. Toxin excretion
18
Q

How much bile is produced a day? Where from?

A

500ml bile everyday.

From hepatocytes (60% - primary) and cholangiocytes (40% - secondary modification).

19
Q

How do cholagniocytes modify bile?

A

Alter pH, reabsorb sugars/acids, secrete HCO3- and Cl-, exocytose IgA

20
Q

Which 2 bile acids does the liver secrete?

A

Cholic acid (becomes deoxycholic acid from gut bacteria)

Chenodeoxycholic acid (becomes lithocholic acid from gut bacteria)

21
Q

What is in bile?

A

Cholesterol
Bile Salts
Bilirubin and drug metabolites

22
Q

What does bile do?

A
  1. Reduce surface tension of fats

2. Aids in micelle formation

23
Q

When is bile released?

A

CCK stimulation

24
Q

Usually bile cannot enter the duodenum straight away. Why?

A

The sphincter of Oddy is contracted

25
Q

What does the GB do?

A
  1. Stores bile (50ml)
  2. Acidifies bile by absorbing HCO3-
  3. Concentrates bile - reabsorbs ions and therefore water. Removes 90% of volume).
26
Q

Give an example of beneficial enterohepatic circulation

A
  1. Recycling of bile salts
27
Q

How might the half life of some drugs be increased?

A

If liver excretes the drug through bile and then faeces. But sometimes bile salts reabsorbed and reenter portal circulation. So half life increased.

28
Q

Describe the concept of the Cori cycle

A
  1. Lactate produced in muscle
  2. Taken to liver
  3. Lactate dehydrogenase converts lactate to pyruvate.
  4. Liver uses 6ATP in gluconeogenesis to form glucose which can then be used by the muscle cell again.
29
Q

Liver needs to make non-essential amino acids. How?

A

It uses transamination reactions. a-ketoglutarate and alanine —> glutamate and pyruvate.

30
Q

Which 3 amino acids can you use to make almost everything else?

A
  1. a-ketoglutarate
  2. pyruvate
  3. oxaloacetate
31
Q

What else does the liver do in terms of protein metabolism?

A

Deamination - urea produced (requires 4 ATP)

32
Q

How does liver contribute to fat metabolism?

A
  1. Liver processes fatty acids into acetyl-CoA which goes into TCA cycle
  2. Lipoprotein synthesis. Can then be used for glycerol, cholesterol, fatty acids
33
Q

If the liver wants a transferable energy source, what does it produce?

A

Acetoacetate (ketone body)

34
Q

What are the components of lipoproteins?

A

TAG + Apoprotein + Phospholipid + Cholesterol

35
Q

What can lipoproteins be made into?

A

HDL - picks up excess cholesterol

VLDL - transports fatty acids to tissues

36
Q

How is detoxification achieved?

A

Phase 1 - make substance more hydrophilic (p450 enzymes)

Phase 2 - attach water soluble side chain makes them less reactive

Alimentary System (15 decks)

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