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GastroIntestinal > Liver As A Storage Organ > Flashcards

Liver As A Storage Organ Flashcards

1
Q

What functions does the liver perform?

A

Carbohydrate metabolism
Fat metabolism
Protein metabolism
Hormone metabolism
Toxin/Drug metabolism and excretion
Storage
Bilirubin metabolism and excretion

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2
Q

What is ferritin?

A

Stored complex of iron

Large spherical protein consisting of 24 non-covalently linked subunits

Subunits form a shell surrounding a central core
Core contains up to 5000 atoms of iron

Ferritin found in the cytoplasm of cells but can also be found in the serum

Concentration of ferritin is directly proportional to the total iron stores in the body

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3
Q

Give examples of excess iron storage disorders

A

Hereditary haemochromatosis
Haemolytic anaemia
Sideroblastic anaemia
Multiple blood transfusions
Iron replacement therapy

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4
Q

What can non-iron overload lead to?

A

Liver disease
Some malignancies
Significant tissue destruction
Acute phase response:
- Inflammation
- Infection
- Autoimmune disorders

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5
Q

What is the cause of low ferritin?

A

Iron deficiency
This can lead to anaemia

Ferritin less than 20 µg/L indicates depletion
Ferritin less than 12 µg/L suggests a complete absence of stored iron

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6
Q

What can vitamins act as?

A

Gene activators
Free-radical scavengers
Coenzymes or cofactors in metabolic reactions

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7
Q

What can excessive ingestion of vitamins result in?

A

Toxicity

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8
Q

Why do water soluble vitamins require more regular intake than fat soluble vitamins?

A

Water soluble vitamins pass more readily through the body

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9
Q

Where can we get Vitamin A (retinal) from?

A

Vertebrates ingest retinal directly from meat or produce retinal from carotenes

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10
Q

What are functions of Vitamin A?

A

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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11
Q

What can Vitamin A deficiency lead to?

A

Rare in affluent countries as vitamin A levels drop only when liver stores are severely depleted

Deficiency may occur due to fat malabsorption

Clinical Features:
Night blindness
Xeropthalmia
Blindness

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12
Q

What can a Vitamin A excess lead to?

A

Acute:
- Abdominal pain, nausea and vomiting
- Severe headaches, dizziness, sluggishness and irritability
- Desquamation of the skin

Chronic:
- Joint and bone pain
- Hair loss, dryness of the lips
- Anorexia
- Weight loss and hepatomegaly

Carotenemia:
- Reversible yellowing of the skin
- Does not cause toxicity

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12
Q

What can a Vitamin A excess lead to?

A

Acute:
- Abdominal pain, nausea and vomiting
- Severe headaches, dizziness, sluggishness and irritability
- Desquamation of the skin

Chronic:
- Joint and bone pain
- Hair loss, dryness of the lips
- Anorexia
- Weight loss and hepatomegaly

Carotenemia:
- Reversible yellowing of the skin
- Does not cause toxicity

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13
Q

What are functions of Vitamin D?

A

Functions:
- Increased intestinal absorption of calcium
- Resorption and formation of bone
- Reduced renal excretion of calcium

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14
Q

What can a deficiency of Vitamin D lead to?

A

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

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15
Q

Where can we get Vitamin D from?

A

Sunlight
Dietary intake (fish and meat)
Supplements

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16
Q

What is Vitamin E stored in?

A

Stored in:
Non-adipose cells such as liver and plasma – labile and fixed pool
Adipose cells – fixed pool

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17
Q

What are the Vitamin E requirement in males?

A

4 mg/day in men

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18
Q

What are the Vitamin E requirements in females?

A

3 mg/day in women

19
Q

What can deficiency in Vitamin E be caused by?

A

Caused by:
- Fat malabsorption (e.g. cystic fibrosis)
- Premature infants
- Rare congenital defects in fat metabolism e.g. abetalipoproteinaemia

Vitamin E excess is relatively safe in excess

20
Q

What are clinical manifestations of Vitamin E?

A

Clinical manifestations:
- Haemolytic anaemia
- Myopathy
- Retinopathy
- Ataxia
- Neuropathy

21
Q

What happens to Vitamin K in the body?

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.

22
Q

What are some sources of Vitamin K?

A

Sources:
- 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)
23
Q

What is the function 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
24
Q

What can a deficiency in Vitamin K lead to?

A
  • Haemorrhagic disease of the newborn:
    Vitamin K injection given to newborn babies
  • Rare in adults, unless on warfarin
25
Q

What can excess of Vitamin K lead to?

A
  • K1 is relatively safe
  • Synthetic forms are more toxic
  • Can result in oxidative damage, red cell fragility and formation of methaemoglobin
26
Q

Where can Vitamin C be found?

A

Fresh fruit and vegetables

27
Q

How much Vitamin C is required in adults a day?

A

Adults need 40 mg/day

28
Q

What are function of Vitamin C?

A

Collagen synthesis
Antioxidant
Iron absorption

29
Q

What can a deficiency in Vitamin C lead to?

A

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

Treatment with vitamin C improves symptoms quickly
- Joint pain gone within 48 hours
- Full recovery within two weeks

30
Q

What can an excess in Vitamin C lead to?

A
  • Doses > 1g/day can cause GI side effects
  • No evidence that increased vitamin C reduces the incidence or duration of colds
31
Q

What are the two active forms of Vitamin B12?

A

Methylcobalamin
5-deoxyadenosylcobalamin

32
Q

What happens to Vitamin B12 in 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.
  • IF-B12 complex absorbed in the terminal ileum.
  • B12 is stored in the liver.
33
Q

What are causes of Vitamin B12 deficiency?

A
  • Pernicious anaemia – autoimmune destruction of IF-producing cells in stomach.
  • Malabsorption – lack of stomach acid, pancreatic disease, small bowel disease.
  • Veganism
34
Q

What are symptoms of Vitamin B12 deficiency?

A

Macrocytic anaemia
Peripheral neuropathy in prolonged deficiency

34
Q

What are symptoms of Vitamin B12 deficiency?

A

Macrocytic anaemia
Peripheral neuropathy in prolonged deficiency

35
Q

What is folate?

A
  • Folate is found in may foods fortified with folic acid.
  • Individuals have higher requirements in pregnancy.
  • Functions as a coenzyme in methylation reactions, DNA synthesis, synthesis of methionine from homocysteine.
36
Q

What are causes of 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)
37
Q

What are symptoms of folate deficiency?

A
  • High homocysteine levels
  • Macrocytic anaemia
  • Foetal development abnormalities (neural tube defects)
38
Q

What is the intrinsic pathway of clotting factors activated by?

A

Contact

38
Q

What is the extrinsic pathway of clotting factors activated by?

A

By FVII coming in contact with tissue factor

39
Q

What do clotting factors initiate?

A

Initiates a cascade which ultimately results in fibrin clot formation

40
Q

Where are clotting factors produced?

A

Produced in the liver
- I (Fibrinogen)
- II (Prothrombin)
- IV
- V
- VI
- VII

41
Q

What can the performance of clotting pathways be measured using?

A
  • Prothrombin time (PT) (extrinsic pathway)
  • International normalised ratio (INR)
  • Activated partial thromboplastin time (aPTT) (intrinsic pathway)

A prolonged PT may indicate a deficiency in the synthetic capacity of the liver

42
Q

What can a prolonged PT also indicate?

A

DIC
Severe GI bleeding
Some drugs
Vitamin K deficiency

GastroIntestinal (19 decks)

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