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Physiology 1 : GI > Intro to functions of the liver > Flashcards

Intro to functions of the liver Flashcards

1
Q

What divides the liver into 2 lobes?

A

→ Falciform ligament

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2
Q

Where is the blood supply of the liver from?

A

→ Portal vein - Blood returning from the GI tract
- 75%
→ 25% - hepatic artery

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3
Q

Where do the central veins of the liver lobules drain?

A

→ Into the hepatic vein

→ Back into the vena cava

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4
Q

What do hepatocytes do?

A

→ 60% perform most metabolic functions

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5
Q

What do Kupffer cells do?

A

→ 30% types of tissue macrophages

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6
Q

What cells other than hepatocytes and kupffer cells does the liver have?

A

→ Stellate

→ Endothelial

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7
Q

What is the functional unit of the liver?

A

→ Hepatic lobule

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8
Q

What is around the central hepatic vein?

A

→ Hexagonal plates of hepatocytes

→ At each of the 6 corners is a triad of branches of the portal vein, hepatic artery and bile duct

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9
Q

Where does blood enter the lobules from and flow to?

A

→ Branches of the portal vein and hepatic artery
→Flows through small channels called sinusoids that are lined with hepatocytes
→ Hepatocytes remove toxic substances from the blood
→ Blood exits the lobule through the central vein

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10
Q

What is the oxygenation like at the hepatic artery?

A

→ Oxygen rich

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11
Q

Why does blood leaving the lobule have low levels of O2?

A

→ Hepatocytes near the sinusoids have used up the O2

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12
Q

Describe the flow of bile

A 
→ Bile is secreted by hepatocytes
→ Series of channels between cells (canaliculi) 
→Small ducts 
→ Large ducts
→ Anastomose onto common bile duct
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13
Q

How does the livers microstructure support its role?

A

→ Large SA - exchange of molecules
→ Sophisticated separation of blood from bile
→ Specific positioning of pumps to achieve localization of materials

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14
Q

How is portal blood filtered?

A

→ Through the sinusoid - removal of gut bacteria

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15
Q

What is bile?

A

→ Complex fluid : Water, electrolytes + mix of organic molecules
→ Organic molecules : bile acids, cholesterol, bilirubin + phospholipids

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16
Q

What are the functions of bile?

A

→ Essential for fat digestion + absorption via emulsification
→ Bile and pancreatic juice neutralize gastric acid as it enters the small intestine
→ Elimination of waste products from blood - bilirubin + cholesterol
→ 500mg of cholesterol converted to bile acids per day

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17
Q

Describe how bile gets to the gall bladder

A 
→ Bile from hepatic ducts 
→ Common bile duct 
→ Duodenum or diverted via cystic duct
→ Gall bladder 
→ Concentrated and stored (30-50ml)
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18
Q

How is entry of bile into the duodenum controlled?

A

→ Opening of the sphincter of Oddi

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19
Q

What is bilirubin?

A

→ Yellow pigment formed from the breakdown of Hb

→ Useless and toxic but made in large quantities so must be eliminated

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20
Q

How are aged RBCs destroyed?

A

→ Dead/ damaged RBCs are digested by macrophages throughout the body
→ Fe is recycled
→ Globin chains are catabolized
→ Hb cannot be recycled so it is eliminated into bilirubin

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21
Q

How is bilirubin formed?

A

→ Heme is converted into free bilirubin in a series of steps
→ Released into the plasma and it is carried around bound to albumin
→ Free bilirubin is absorbed by hepatocytes and conjugated with glucuronic acid
→ Conjugated bilirubin is secreted into bile and metabolized by bacteria in the intestinal lumen
→ Eliminated in feces + urine

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22
Q

What is the major metabolite in feces?

A

→ Stercobilin

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23
Q

What is the major metabolite in urine?

A

→ Urobilin and urobilinogen

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24
Q

How is jaundice caused?

A

→ Excessive quantities of free or conjugated bilirubin accumulate in ECF

25
Q

What are the symptoms of jaundice?

A

→ Yellow discolouration of the skin, sclera and mucous membranes

26
Q

What is green jaundice caused by?

A

→ mutation of biliverdin reductase

27
Q

What is pre hepatic jaundice?

A

→ excessive RBC breakdown

→ Excess unconjugated bilirubin is not excreted & remains in circulation

28
Q

What is hepatic jaundice?

A

→ Hepatocyte damage

→Excess conjugated &/ unconjugated bilirubin

29
Q

What is post hepatic jaundice?

A

→ excess conjugated bilirubin
→ Obstruction into passage of duodenum
→ Enters circulation & into urine
→ pruritus

30
Q

What is used for neonatal jaundice in low resource countries?

A

→ Sunlight canopies

31
Q

What toxic substances does the liver metabolize?

A

→ bilirubin
→ ammonia
→ hormones
→ Drugs & exogenous toxins

32
Q

How are steroid hormones inactivated?

A

→ By conjugation & excretion

33
Q

Describe phase 1 of the liver metabolizing drugs

A

Oxidation & Reduction
→ occurs in smooth ER
→ Catalyzed by cytochrome P450
→ Makes substrate into a polar compound

34
Q

Describe phase 2 of the liver metabolizing drugs

A

Conjugation
→ Makes the drug more water soluble
→ Glucuronyl is the most prevalent conjugation group
→ Not all drugs use both phases
→ Elimination via ATPase pumps into blood or bile

35
Q

Why is accidental overdose common with paracetamol?

A

→ Narrow therapeutic index

36
Q

When should paracetamol not be taken?

A

→ After alcohol consumption

37
Q

What are the 3 pathways that paracetamol is metabolized by?

A

→ Glucuronidation - 45-55%
→ Sulfation - 20-30%
→ N-hydroxylation & dehydration - < 15% (intermediate NAPQI is toxic)

38
Q

What happens to paracetamol metabolism if you overdose?

A

→ Liver enzymes become saturated and glutathione stores are depleted

39
Q

What is the treatment for paracetamol overdose?

A

→ N-acetyl cysteine is given which is a precursor to glutathione

40
Q

Why does the body have to oxidize alcohol?

A

→ To remove it

→ It cannot be stored

41
Q

What happens after alcohol is metabolized by liver enzymes?

A

→ It enters normal metabolic pathways and is metabolized as fat

42
Q

What are the steps to metabolize alcohol?

A

→Ethanol → Acetaldehyde by alcohol dehydrogenase

→Excess NADH produced by oxidation must be removed

→Pyruvic acid → Lactic acid - requires NADH

→ Pyruvic acid + NADH + H+ → Lactic acid + NAD+

43
Q

What can excess NADH be used as?

A

→ A reducing agent in pathways involved in lipogenesis
→ Synthesize glycerol
→ Synthesize fatty acids

44
Q

What can NADH directly be used in?

A

→ The electron transport chain to synthesize ATP

45
Q

What does NADH inhibit?

A

→ Normal oxidation of fats and fats may accumulate

46
Q

How can accumulation of fats in the liver be alleviated?

A

→ By secreting lipids into the blood

47
Q

What does excess acetaldehyde lead to and why?

A

→ Acetaldehyde is toxic

→ Hepatitis and cirrhosis occur

48
Q

What are three problems associated with drinking?

A

→ Fatty liver
→ Alcoholic hepatitis
→ Alcoholic cirrhosis

49
Q

How does fatty liver arise?

A

→ Alcohol abuse can lead to the accumulation of fat within liver cells

50
Q

What is cirrhosis?

A

→ A degenerative disease where liver cells are damaged and replaced by scar formation

51
Q

What can be an effect of impaired detoxification?

A

→ Gynecomastia

52
Q

What blood clotting factors are made in the liver?

A

→ Fibrinogen
→ Prothrombin
→ V, VI, IX, X, XII

53
Q

What is needed to make all the clotting factors?

A

→ Vitamin K

54
Q

What do stellate cells act as?

A

→ Important deports for storage of fat soluble vitamins (A,D,E,K)

55
Q

What does liver dysfunction lead to?

A

→ Fat malabsorption

→ Vitamin deficiency

56
Q

What vitamin does the liver store?

A

→ Vitamin B12

→ Folate

57
Q

What happens with a vitamin B12 deficiency?

A

→ Pernicious anaemia

58
Q

How is iron stored in the liver?

A

→ As ferritin

Physiology 1 : GI (15 decks)

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