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GI > The liver > Flashcards

The liver Flashcards

1
Q

Describe the blood supply to the liver

A
  • Double blood supply
  • Hepatic artery (rich in oxygen, 30% of hepatic blood)
  • Portal vein (from gut, 70% hepatic blood, rich in nutrients, poor in oxygen)
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2
Q

Where does the portal vein come from?

A
  • Intestine
  • Pancreas
  • Spleen
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3
Q

Describe the venous drainage of the liver

A
  • Vessels merge to form hepatic veins

- These merge to cauda vena cave to go back to heart

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4
Q

Name the lobes of the liver

A
  • Quadrate in the middle
  • Left and right each divided into lateral and medial
  • Caudate (very caudal)
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5
Q

Describe the histological layers of the liver

A
  • M esothelium on the outside (peritoneum) (single layer of cells)
  • Then hepatic (Glisson’s capsule)
  • Then hepatocytes
  • Hepatic stroma made up of thin fibres of connective tissue
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6
Q

Describe the portal triad in the liver

A
  • Made up of hepatic artery, portal vein and bile duct
  • Surrounded by connective tissue
  • If very large may also contain lymphatic vessels and autonomic nerves
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7
Q

What are hepatic sinusoids?

A
  • Fenestrated blood vessels running along the plates of hepatocytes
  • Portal and hepatic arterial blood mix in the sinusoids
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8
Q

What are the central veins?

A
  • Found at the centre of classic hepatic lobule

- Receive blood from siusoids, return to circulation via hepatic vein

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9
Q

What cells make up the walls of bile ducts?

A

Simple cuboidal epithelium

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10
Q

What cells make up the walls of the blood vessels?

A
  • Flat endothelial

- Thinner endothelium is vein, thicker is artery

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11
Q

Describe the arrangement of the hepatocytes

A
  • Arranged into plates
  • Have junctions
  • Plates arrange to form the sinusoids
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12
Q

What is the limiting plate?

A

The discontinuous border of hepatocytes that forms the outer boundary of the portal tract

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13
Q

Describe the classical hepatic lobule

A
  • Hexagonal shape

- Lines between portal triads with central vein in the centre

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14
Q

Describe the portal lobule

A
  • Portal triad in the centre
  • Triangular shape
  • Points at central veins
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15
Q

Describe the hepatic acinus

A
  • Oval shape
  • Each end is central vein
  • Sides at portal triads
  • Can be divided into zones 1, 2 and 3
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16
Q

Compare the flow of the blood and bile in the liver

A
  • Blood flows out of vessels and into sinusoids
  • Bile being produced by hepatocytes and flows in opposite direction in bile ducts
  • Blood and bile to not mix, are not within sma structure
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17
Q

Describe zone 1 of the portal acinus

A
  • Closest to portal tract
  • Receives most oxygenated blood
  • Susceptivble to direct acting toxicants
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18
Q

Describe zone 3 of the portal acinus

A
  • Furthest away
  • Receives least blood
  • Highest biotransformative/detoxification activity
  • More P450 cytochrome enzyme present (metabolises toxins)
  • More susceptive to hypoxic injury
  • Injury by toxic substances that are metabolically activated by P450
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19
Q

Name the 4 main cell types found in the liver

A
  • Hepatoytes
  • Endothelial cells
  • Kupffer cells (sinusoidal macrophages)
  • Ito cells (hepatic stellate cells
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20
Q

Where are Ito cells found?

A
  • Between endothelial cells adn hepatocytes may have space of Disse
  • Ito cells found in this space
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21
Q

Describe the morphology of hepatocytes

A
  • Polyhedral
  • Round nucleus
  • Prominent nucleolus
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22
Q

Describe the functions of the hepatocytes

A
  • Most hepatic functions
  • Metabolise and store minerals absorbed from small intestine
  • Secrete bile
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23
Q

Desribe the morphology of Kupffer cells

A

Macrophage like

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24
Q

Describe the functions of Kupffer cells

A

Defend against vascular-carried pathogens and remove debris

25
Q

Describe the morphology of Ito cells

A
  • Contain big intracytoplasmatic vacuoles (lipid)

- Nucleus at periphery

26
Q

Describe the functions of Ito cells

A
  • Involved in tissue fibrosis

- Involved in retinol metabolism (store vit A)

27
Q

Describe the biliary tree in the liver

A
  • Bile canaliculi are intercellular channels formed between adjacent hepatocytes, isolated by occluding junctions
  • Canals of Hering between the bile canaliculi and bile ducts
  • Drainage is from bile ducts of portal tracts
28
Q

Describe the function of smooth endoplasmic reticulum in hepatocytes

A
  • Contains main enzyme of detoxification (cytochrome P450)

- Involved in lipid and glycogen metabolism

29
Q

Desribe the function of peroxisomes in hepatocytes

A

Contain enzymes involved in detoxification (catalase)

30
Q

Describe the function of the rough endoplasmic reticulum in hepatocytes

A
  • Binds ribosomes engaged in translating mRNA to proteins

- Protein and lipid modifications

31
Q

Describe the function of the golgi apparatus

A
  • Associated with protein secretion (important for bile secretion)
  • Involved in protein and lipid modifications
32
Q

Describe the function of mitochondria

A

Aerobic energy supply (ATP production)

33
Q

Describe the function of lysosomes in hepatocutes

A

Digestion of macromolecules

34
Q

Describe the function of glycogen

A

Short term storage of glucose

35
Q

Describe the function of lipid droplets in hepatocytes

A

Storage of esterified fatty acids

36
Q

What is the function of the gall bladder?

A

Storage, concentration and release of bile

37
Q

What is the function of bile?

A
  • Fat digestion

- Hepatic excretion

38
Q

What are the histological layers of the gall bladder?

A
  • Mucosa (epithelium, lamina propria)
  • Muscular layer
  • Adventitia/serosa
  • NO MUSCULARIS MUCOSAE OR SUBMUCOSA
39
Q

Describe the structure of the gall bladder

A
  • Fibromuscular sac lined by simple columnar epithelium

- Folds if not distended

40
Q

Describe the role of the liver in detoxification of foreign chemicals

A
  • Exogenous matter
  • Dose makes poison (anything toxic in right amount)
  • Liver can identify and detoxify chemicals that are in excess of normal
  • Turn over of drugs in body controlled by cytochrome P450
  • Hydrophilic drugs excreteed easily
  • Hydrophobic go to liver, CYPs add reactive handle so can be acted on (phase 1)
  • In phase 2 conjugated handle worked on to make it polar and be excreted
41
Q

Describe the removal of endogenous waste in the liver

A
  • Haem breakdown in macrophages
  • Damaged RBCs taken up by macrophages, haem portion and globin portion
  • From globin portion derive amino acids
  • High quantitiy of bilirubin produced, goes to bile, excreted by liver
  • Iron stored as ferritin and can be reused
  • Albumin transports things in blood, conjugates with bilirubin and takes it to liver
  • Secreted via bile
  • Small amount of urobilinogen reabsorbed from SI, most excreted
42
Q

Describe the role of the liver in nitrogen excretion

A
  • In absortpive state and post-absorptive state ammonia needs to be dealt with
  • AA produced, excreted as urea
  • Ammonia toxic, excreted a urea
  • Shuttled back to liver by hepatic portal vein
43
Q

Describe the role of the liver in energy metabolism and homeostasis

A
  • Central control of metabolism
  • Without cannot maintain homeostasis
  • Glycolysis, gluconeogenesis, glycogenolysis etc all take place in liver
  • Maintain blood glucose levels
44
Q

Describe the clinically important liver enzymes

A
  • Aspartate aminotransferase (AST)
  • Alanine amio transferase (ALT)
  • Compare ratios of these to asses liver function
45
Q

List the important plasma proteins

A
  • Serum albumin
  • VLDL, HDL
  • Fibrinogen and prothrombin
  • Transferrin
  • Complement proteins
46
Q

What is the role of serum albumin?

A
  • Highly abundant
  • Carrier protein for anything that needs to travel in blood stream but is too small to do so itself
  • Maintains osmotic pressure
  • Synthesised exclusively by hepatocytes
  • Hypoalbuminemia not specieif for liver disease
47
Q

What is the role of fibrinogen and prothrombin

A

Needed in coagulation cascade

48
Q

Describe the role of transferrin

A
  • Iron transport

- Produced in liver to an extent but mostly elsewhere

49
Q

Describe apolipoproteins

A
  • Each lipoprotein has own set of apolipoproteins
  • Are functional proteins
  • Activate enzymes
  • Bind receptors
  • Stabilise lipoprotein
50
Q

Describe amino acid metabolism in the liver

A
  • Used in urea cycle
  • Ornithine takes up ammonia molecule, form scitrulline via carbomoyl phosphate, conversion back through arginine = ornithine and molecule of urea
  • Not used in fish or birds
51
Q

Describe the role of the liver in lipid metabolism

A
  • Bile sats needed to produce smaller fat droplets
  • Produced in liver
  • Form amphipillic micelles with lipidcore, water soluble exterior
  • Once larger made smaller have action of pancreatic lipase
  • Degradationof products and produce micelles
  • Pores on these micelles allow monoglycerides and FFAs to be released into enterocyte to be absorbed by gut
  • TAGs resynthesised and form chylomicrons within enterocytes
52
Q

Desribe the role of the liver in cholesterol production

A
  • 3 carbon molecule ACA converted to 6 carbon mevalonate via HMG-CoA (enzymatic process)
  • Mevaloate loses a carbon by decarboxylation => 5 carbon isoprene
  • 30 carbon squalene produed by joining these
  • Goes on to form cholesterol via lanosterol
  • Once C6 produced commited to cholesterol production
53
Q

How do statins prevent cholesterol production?

A
  • Prevent reduction from C3 to C6 molecule

- Once C6 produced, commited to cholesterol production

54
Q

Where on the cholesterol structure are steroid hormones modified?

A

Carbon 17

55
Q

List substances synthesised by the liver

A
  • Cholesterol
  • Glycogen
  • Bile acids
  • TAGs
56
Q

Describe the role of the liver in immune regulation

A
  • Kupffer cells
  • Complement synthesis and metabolism
  • Line walls of sinusoids
  • Mostly for breakdown of RBCs
  • Also pick up bacteria and otehr particles absorbed from gut
  • Screen and stop bacteria entering systemic circulation
57
Q

What molecules are stored in the liver

A
  • Glycogen
  • Water soluble vitamins
  • Fat soluble vitamins
  • Iron
58
Q

Desribe the role of the liver in the production of clotting factors

A
  • Liver synthesises all coagulation factors except VIII (Von Willebrand’s)
  • Among these are vitamin K-dependent factors (2, 7, 9, 10)
  • Also synthesises inhibitors of coagulation and fibrinolysis and fibrinolytic proteins
  • Clears and catabolises activated coagulation factors, plasminogen activators adn breakdown of products of fibrinolysis such as fibrin degradation products

GI (31 decks)

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