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Clinical Biochem > Anatomy & Function of the Liver > Flashcards

Anatomy & Function of the Liver Flashcards

1
Q

Where is the liver located ?

A

upper right-hand portion of the abdominal cavity
- beneath the diaphragm
- ontop of the stomach

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2
Q

What is the overall structure of the liver?

A
  • 2 lobes
  • each lobe is made up of 8 segments that consist of 1000 lobules
  • lobules are connected to small ducts connected to larger ducts to form the common hepatic duct
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3
Q

What is the function of the common hepatic duct ?

A
  • transports bile made by the liver cells to the gallbladder & duodenum
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4
Q

Describe why the liver is a vascular organ ?

A
  • hepatic artery = supplies 02 rich blood from heart to liver
  • portal vein = supplies nutrient rich blood from digestive tract
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5
Q

What is present in every liver lobule ?

A
  • serval portal triads
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6
Q

What 5 structures make up a portal triad ?

A
  1. proper hepatic artery
  2. hepatic portal vein
  3. 1/2 small bile ducts
  4. lymphatic vessels
  5. branch of the vagus nerve
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7
Q

Describe the proper hepatic artery

A
  • an arteriole branch of the hepatic artery that supplies oxygen
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8
Q

Describe the hepatic portal vein

A
  • a venue branch of the portal vein, with blood rich in nutrients but low in oxygen
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9
Q

What are the functions of the liver ?

A
  • manufactures bile
  • controlling levels of fats, amino acids & glucose
  • cholesterol synthesis
  • clears blood of infections
  • stores iron & vitamins
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9
Q

Where is bile produced ?

A

the liver

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10
Q

Where is bile stored ?

A

in the gallbladder

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11
Q

What is the function of bile ?

A
  • required for digestion & fat absorption
  • endogenous synthesis of bile salts
  • absorption of fat soluble vitamins
  • major route for loss of cholesterol
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12
Q

What is the composition of bile ?

A
  • bile salts
  • phospholipids
  • cholesterol
  • bilirubin
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13
Q

What synthesises bile salts ?

A
  • hepatocytes
  • bile piglets are picked up from blood sinusoids
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14
Q

What is the daily secretion of bile ?

A

500 mls

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15
Q

What are bile acids formed from ?

A
  • cholesterol in the liver
  • conjugated with glycine & taurine
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16
Q

What is the process of metabolism of bile salts in the liver ?

A
  1. biosynthesis of bile acids from cholesterol
  2. conjugation with amino acids
  3. conc. in gallbladder by removal of water
    4/5. intestinal bacteria in colon produce enzyme that can attack/alter bile salts
  4. most bile acids are reabsorbed from intestine, transported to liver and reverted to bile
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17
Q

Define enterohepatic circulation

A

the process by which substances are metabolised by the liver, secreted into liver and then reabsorbed into the body

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18
Q

Describe the metabolism of bilirubin

A
  • 120 days RBCs are phagocytised & haemoglobin is released
  • haemoglobin is broken down into Haem, globin & iron
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19
Q

What happens to haem in the blood ?

A

its converted to bilirubin

20
Q

What happens to globin in the blood ?

A

it’s broken down into amino acids & recycled

21
Q

What happens to iron in the blood ?

A
  • bound by transferrin & returned to iron stored in the liver or bone marrow
22
Q

Where is bilirubin degraded ?

A

-intestines
- intestinal bacteria degrade conjugated bilirubin to form urobilinogen

22
Q

What happens to bilirubin at the liver ?

A
  • unconjugated bilirubin flows into sinusoidal tissue, albumin releases it
  • ligandin binds to unconjugated bilirubin presents it to glucuronic acid
  • in the liver it becomes conjugated by UDP-glucuronyl transferase
23
Q

What happens to 80% of urobilinogen ?

A
  • its oxidised to stercobilin & excreted in faeces, giving stool brown colour
24
Q

What happens to 20% of urobilinogen ?

A
  • absorbed by extra hepatic circulation to be recycled through liver & re-excreted
  • enters systemic circulation to be filtered by kidneys & excreted via urine
25
Q

What are the main 2 functions of the liver in iron homeostasis ?

A
  1. major site of iron storage, regulates iron traffic into/around body via production of peptide hepcidin
  2. site of synthesis of major proteins in iron metabolism
26
Q

What does hecidin do?

A
  • binds to ferroportin, inhibiting iron absorption/efflux
27
Q

Where are coagulation factors mainly synthesised ?

A
  • in the liver
28
Q

What is the function of Liver Function Tests (LFTs) ?

A
  1. Detect presence of disease
  2. distinguish different types of liver disorders
  3. extent of liver damage
  4. follow response to treatment
29
Q

How is the sample for an LFT taken?

A
  • test is done on serum of patient
  • random sample can be taken
  • serum is stable for 3 days a 1-6 degrees
30
Q

What are some precautions that should be taken with an LFT ?

A
  • Avoid haemolytic
  • for bilirubin fasting sample is preferred
  • protect serum/plasma from light
31
Q

What are the 2 subdivisions of LFTs?

A
  1. true tests of liver function 2. tests indication liver injury or biliary tract disease
32
Q

How are different LFTs classified ?

A
  • based on major functions
    1. excretion
    2. serum enzymes
    3. synthetic function
33
Q

Describe an Excretion LFT

A
  • serum bilirubin
  • true test of liver function as it reflects livers ability to take up, process & secrete bilirubin into the bile
  • conjugated = direct - excreted by kidney
  • unconjugated = indirect - bound to albumin
34
Q

What enzymes reflect damage to hepatocytes ?

A
  • aspartate aminotransferase (AST)
  • alanine aminotransferase (ALT)

These are sensitive indicators of liver cell injury

35
Q

Where are aspartate aminotransferase found ?

A

liver, cardiac muscle, kidneys, brain & erythrocytes

36
Q

Describe Aminotransferase

A
  • normal = 10-40 U/L
  • <300 U/L nonspecific may be found in any liver disorder
  • > 1000 U/L = extensive hepatocellular injury = viral hepatitis, ischaemic liver injury or acute heart failure
37
Q

Describe the pattern of aminotransferase in different diseases ?

A
  • acute hepatocellular disorders = ALT > AST
  • chronic viral hepatitis = ALT > AST
  • Cirrhosis = AST > ALT
38
Q

What does enzymes reflect cholestasis ?

A
  • alkaline phosphatase
  • gamma glutamyl transpeptidase
39
Q

Describe Alkaline Phosphatase

A
  • not specific for cholestasis
  • < 3 fold in any type of liver disease
  • > 4 fold in cholestatic liver disorders & infiltrative disease such as cancer
40
Q

What are some examples of why non pathological elevation of alkaline phosphatase can occur ?

A
  • Age over 60
  • rapid bone growth
  • late pregnancy
41
Q

What can hypoalbuminaemia reflect ?

A
  • common in chronic liver disorders = cirrhosis
  • reflects severe liver damage & decreased albumin synthesis
  • not specific for liver disease
42
Q

Describe LFT measuring Prothrombin time (PT)

A
  • prothrombin = plasma protein converted into thrombin during blood clotting
  • formed in liver from inactive preprothrombin in the presence of Vit K
  • Used to assess activity of extrinsic blood clotting pathway
43
Q

What is the PT test expressed as ?

A

International Normalised Ration I(NR)
- Based on ratio of patients prothrombin time & normal mean prothrombin time

44
Q

Which lobe of the liver is the largest ?

A
  • the right lobe
45
Q

Which cells in the liver are responsible for phagocytosis ?

A
  • Kupffer cells
46
Q

Which vitamin is stored in significant amounts in the liver ?

A
  • Vitamin A
47
Q

Which substances does the liver detoxify ?

A
  • drugs, alcohol & ammonia

Clinical Biochem (11 decks)

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