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GI Lectures > The Liver As A Storage Organ > Flashcards

The Liver As A Storage Organ Flashcards

1
Q

What function does the liver have?

A

What functions does the liver perform?
Carbohydrate metabolism
Fat metabolism
Protein metabolism
Hormone metabolism
Toxin/Drug metabolism and excretion
Storage
Bilirubin metabolism and excret

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2
Q

How is iron transported?

A

Through transferrin

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3
Q

How is iron used in the body?

A
  • Bone marrow: circulating erythrocytes (heamoglobin)
  • Muscle (myoglobin)
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4
Q

Where is iron stored?

A
  • In the liver parenchyma
  • In the reticuloendothelial macrophages
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5
Q

How is Iron lost?

A
  • Sloughed mucosal cells (loss of tissue cells)
  • Desquamation (skin sheds)
  • Mestruation
  • Other blood loss
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6
Q

What is the structure of ferritin?

A
  • Large spherical protein consisting of 24 no-covalently linked subunits
  • Core contains up to 5000 atoms of iron (high conc)
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7
Q

Where is ferritin found?

A
  • In the cytoplasm of cells but can also be found in the serum (blood)
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8
Q

What does the concentration of ferritin tell us?

A

Directly proportional to the total iron stores in the body
- therefore we can use it if we think a patient has an iron deficiency

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9
Q

What are some excess iron storage disorders due to ferritin excess?

A
  • Hereditary haemochromatosis
  • Haemolytic anaemia
  • Sideroblastic anaemia
  • Multiple blood transfusions
  • Iron replacement therapy
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10
Q

What are some non-iron overload conditions that cause ferritin excess?

A
  • Liver disease
  • Some malignancies
  • Significant tissue destruction
  • Acute phase response:
    Inflammation
    Infection
    Autoimmune disorders
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11
Q

What causes low ferritin deficiency?

A

Iron deficiency
- This can result in anaemia
- Ferritin less than 20 ug/L indicates depletion
- Ferritin less than 12 ug/L suggests a complete absence of stored iron

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12
Q

What is the RDA and AI?

A

RDA - Recommended daily allowance
AI - Adequate intake

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13
Q

How do vitamins benefit the body?

A
  • Gene activators
  • Free-radical scavengers
  • Coenzymes or cofactors in metabolic reactions
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14
Q

What can excessive vitamin ingestion lead to?

A

Can result in toxicity

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15
Q

What is the difference between water and fat soluble vitamins in terms of movement?

A

Water soluble vitamins pass more readily through the body, therefore, require more regular intake than fat soluble vitamins
- So fat soluble vitamins are much better at storage

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16
Q

Is vitamin A a fat soluble or water soluble vitamin?

A

Fat soluble

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17
Q

What can we eat to gain Vitamin A?

A

Vertebrates ingest retinal directly from meat or produce retinal from carotenes (found in fruit and veg)

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18
Q

What are the functions of vitamin A?

A
  • It is important for sight and vision: Used to form rhodopsin in the rod cells in the retina
  • Reproduction: Spermatogenesis in male
    Prevention of foetal resorption of female
  • Growth
  • Stabilisation of cellular membranes
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19
Q

How much vitamin A do we need to intake each day?

A

0.6 mg/day in men, 0.7 mg/day in women

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20
Q

What happens when we have a vitamin A deficiency?

A
  • Rare in affluent countries as vitamin A levels drop only when liver stores are severely depleted.
  • Deficiency may occur due to fat malabsorption
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21
Q

What are the clinical features to look out for with a Vitamin A deficiency?

A

Clinical Features:
Night blindness
Xeropthalmia
Blindness

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22
Q

What are the symptoms of vitamin A in excess in acute cases?

A

Abdominal pain, nausea and vomiting
Severe headaches, dizziness, sluggishness and irritability
Desquamation of the skin (skin peeling)

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23
Q

What are the symptoms of vitamin A in excess in chronic cases?

A

Joint and bone pain
Hair loss, dryness of the lips
Anorexia
Weight loss and hepatomegaly (enlarged liver)

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24
Q

What is carotenemia and what causes it?

A

Reversible yellowing of the skin
Does not cause toxicity
Caused by Vitamin A excess

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25
Q

What are the functions of Vitamin D?

A
  • Increased intestinal absorption of calcium
  • Resorption and formation of bone
  • Reduced renal excretion of calcium
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26
Q

What happens when there is a vitamin D deficiency?

A

Demineralisation of bone:
- Rickets in children
- Osteomalacia in adults

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27
Q

Where can we get vitamin D from?

A

Sunlight, fish, meat, supplements

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28
Q

Where is vitamin E stored?

A
  • Non-adipose cells such as liver and plasma: labile and fixed pool
  • Adipose cells: fixed pool
29
Q

What is the function of vitamin E?

A

Important antioxidant

30
Q

What are the vitamin E requirements?

A

4 mg/day in men
3 mg/day in women

31
Q

Where can you get vitamin E from?

A

almonds, hazelnuts, oil, spinach, carrots, avocado

32
Q

What is a vitamin E deficiency caused by?

A
  • Fat malabsorption (e.g. cystic fibrosis)
  • Premature infants
  • Rare congenital defects in fat metabolism e.g. abetalipoproteinaemia.
33
Q

What are the clinical manifestations of a vitamin E deficiency?

A

Haemolytic anaemia
Myopathy
Retinopathy
Ataxia
Neuropathy

34
Q

What happens when we have vitamin E in excess?

A

relatively safe

35
Q

How is vitamin K taken up?

A

Vitamin K is rapidly taken up by the liver but then is transferred to very low-density lipoproteins and low density lipoproteins which carry it into the plasma.

36
Q

What are some sources of vitamin K?

A
  • Vitamin K1 (phylloquinone)
    Synthesized by plants and present in food
  • Vitamin K2 (menaquinone)
    Synthesized in humans by intestinal bacteria
  • Synthetic vitamin K’s:
    K3 (menadione)
    K4 (menadiol)
37
Q

What are the functions of vitamin K?

A
  • Vitamin K is responsible for the activation of some blood clotting factors.
  • Necessary for liver synthesis of plasma clotting factors II, VII, IX and X.
  • Can be assessed by measuring prothrombin time.
38
Q

What happens when we have a deficiency of vitamin K?

A
  • Haemorrhagic disease of the newborn:
    Vitamin K injection given to newborn babies
  • Rare in adults, unless on warfarin.
39
Q

What happens when we have an excess of vitamin K?

A
  • K1 is relatively safe
  • Synthetic forms are more toxic
  • Can result in oxidative damage, red cell fragility and formation of methaemoglobin.
40
Q

Is vitamin K a fat soluble or water soluble vitamin?

A

fat soluble

41
Q

Is vitamin E a fat soluble or water soluble vitamin?

A

fat soluble

42
Q

Is vitamin D a fat soluble or water soluble vitamin?

A

fat soluble

43
Q

Is vitamin C a fat soluble or water soluble vitamin?

A

water soluble

44
Q

Is vitamin B12 a fat soluble or water soluble vitamin?

A

water soluble

45
Q

Is folate a fat soluble or water soluble vitamin?

A

water soluble

46
Q

Where is vitamin C found?

A

fresh fruit and veg

47
Q

How much vitamin C does an adult need?

A

40mg/day (a lot more than fat soluble vitamins)

48
Q

What are the functions of vitamin C?

A
  • Collagen synthesis
  • Antioxidant
  • Iron absorption
49
Q

What happens when there is a vitamin C deficiency?

A

Deficiency – Scurvy
- Easy bruising and bleeding
- Teeth and gum disease
- Hair loss

50
Q

What happens to improve vitamin C deficiency?

A
  • Treatment with vitamin C improves symptoms quickly
  • Joint pain gone within 48 hours
  • Full recovery within two weeks
51
Q

What happens when there is an excess of vitamin C?

A
  • Doses > 1g/day can cause GI side effects
  • No evidence that increased vitamin C reduces the incidence or duration of colds.
52
Q

What are the two forms of Vitamin B12?

A
  • Methylcobalamin
  • 5-deoxyadenosylcobalamin
53
Q

How is vitamin B12 absorbed by the body?

A
  • Released from food by acid and enzymes in the stomach
  • Binds to R protein to protect it from stomach acid
  • Released from R proteins by pancreatic polypeptide.
  • Intrinsic factor (IF) produced by the stomach needed for absorption.
54
Q

Where is vitamin B12 absorbed and stored?

A

IF-B12 complex absorbed in the terminal ileum.
B12 is stored in the liver.

55
Q

What are the causes of a B12 deficiency?

A
  • Pernicious anaemia: autoimmune destruction of IF-producing cells in stomach so can’t absorb B12
  • Malabsorption: lack of stomach acid, pancreatic disease, small bowel disease.
  • Veganism
56
Q

What are the symptoms of a B12 deficiency?

A
  • Macrocytic anaemia
  • Peripheral neuropathy in prolonged deficiency
57
Q

What foods have vitamin B12 in them?

A

meat, fish, eggs, dairy

58
Q

Where is folate found?

A

Many foods are fortified with folic acid

59
Q

Why would someone need higher levels of folic acid?

A

if they were pregnant

60
Q

What are the functions of folate?

A

Functions as a coenzyme in methylation reactions, DNA synthesis, synthesis of methionine from homocysteine

61
Q

What are the causes of a folate deficiency?

A
  • Malabsorption
  • Drugs that interfere with folic acid metabolism (anticonvulsants, methotrexate)
  • Disease states that increase cell turnover (e.g. leukaemia, haemolytic anaemia, psoriasis)
62
Q

What are the symptoms of a folate deficiency?

A
  • High homocysteine levels
  • Macrocytic anaemia
  • Foetal development abnormalities (neural tube defects)
63
Q

What are the 2 coagulation cascades for clotting?

A

Intrinsic pathway and extrinsic pathway

64
Q

What number clotting factors are needed for the intrinsic pathway?

A

XII, XI, IX, VIII

65
Q

What number clotting factors are needed for the extrinsic pathway?

A

VII activates it by coming in to contact with tissue factor which initiates a cascade which ultimately results in fibrin clot formation

66
Q

Where are clotting factors I (Fibrinogen), II (Prothrombin), IV ,V, VI, VII produced?

A

In the liver

67
Q

How do we measure how well clotting pathways are working?

A

See how long it takes for someones blood to clot

68
Q

What are the two ways to measure how well clotting pathways are working?

A
  • Prothrombin time (PT) (extrinsic pathway) also called…
    International normalised ratio (INR) - Normally done on ppl who take warfarin as a regular check
  • Activated partial thromboplastin time (aPTT) (intrinsic pathway)
69
Q

What would a prolonged PT test indicate?

A
  • A prolonged PT may indicate a deficiency in the synthetic capacity of the liver.
  • Prolonged PT is not specific for liver disease can be due to:
    DIC
    Severe GI bleeding
    Some drugs
    Vitamin K deficiency

GI Lectures (14 decks)

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