Liver as a storage organ Flashcards
What are the functions of the liver?
Metabolism of fat, protein, carbohydrate, hormones
Toxin/drug metabolism and excretion
storage
bilirubin metabolism and excretion
Where is iron absorbed?
Where in the body is iron used?
duodenum
bone marrow - used to make red blood cells
muscles - used to make myoglobin
stored in the liver
How is iron lost from the body?
sloughed mucosal cells
desquamation
menstruation
blood loss
very little is lost overall
What is ferritin?
large spherical protein found in cytoplasm of cells, can be in serum.
subunits form a shell surrounding a central core
core contains up to 5000 atoms of iron
How does the body store iron?
ferritin protein
What causes ferritin to rise in the blood?
Excess iron storage disorders - iron overload
or
non-iron overload - unrealated things that cause a rise in the blood
e.g. liver disease or acute phase response
What causes ferritin deficiency? What shows it?
Iron deficiency - only significant known cause
Low concentration in the blood
What do vitamins act as?
gene activators
- free-radical scavengers
- coenzymes or cofactors in metabolic reactions
Difference between fat and water soluble vitamins?
Water soluble pass more readily through the body so require more regular intake than fat soluble
Vitamin A
Fat soluble
Retinoids
Meat and dairy products -
Converted from carotenes - carrots, sweet potatoes, tomatoes, spinach
Requirements for Vitamin A?
0.6 mg/day men
0.7 women
Functions of Vitamin A?
Vision
- forms rhodopsin in rod cells
Reproduction
-spermatogenesis
- prevent reabsorption of fetus
Growth
Stabilisation of cellular membranes
Vitamin A deficiency?
Vitamin A excess?
Rare in more developed countries
May occur due to fat
ELEPHANT
Vitamin D functions?
Increase intestinal absorption of calcium
Reabsorption and formation of bone
Reduced renal excretion of calcium
What happens in a vitamin D deficiency?
demineralisation of bone
- rickets in children
- osteomalacia in adults
WHerre is vitamin D found?
sunlight and fish/meat or supplements
stored in liver, when needed goes to the kidneys
Converted to form that performs these functions
Where is vitamin E stored?
Fat soluble
Adipose cells - fixed pool
Non-adopose cells - liver and plasma - labile and fixed pool
Where is vitamin E absorbed from?
almonds
avocadoes
spinach
carrots
oils
etc
Role of vitamin E?
important antioxidant
4mg/day men
3 women
Vitamin E deficiency
caused by?
clinical manifestation?
Vitamin E excess?
- fat malabsorption, premature infants, rare congenital defects
- haemolytic anaemia, myopathy, retinopathy, ataxia, neuropathy
- relatively safe in excess
Where Vitamin K stored?
rapid take up by the liver
transferred to very low density lipoproteins
and low density lipoproteins that carry it to the plasma
Sources of Vitamin K
Functions of Vitamin K?
Activation of blood clotting factors
necessary for liver synthesis of plasma clotting factors II, VII, IX and X
Can be…
Deficiency and excess of Vitamin K?
What are the fat soluble vitamins?
A, E, D, K
Where is vitmin C found?
Requirements per day?
Fresh fruit and veg
40 mg/day
Functions of vitamin C?
collagen synthesis
antioxidant
iron absorption
Vitamin C deficiency?
Scurvy
-easy bruising and bleeding
- teeth and gum disease
- hair loss
treatment with vitamin C improves symptoms quickly
Vitamin C excess?
doses >1g/day - GI side effects
no evidence it helps colds
Is vitamin C water or fat soluble?
water soluble
What are the 2 active forms of VB12?
methylcobalamin
5-deoxyadenosylcobalamin
Absorption of vitamin B12?
released from food
binds to R protein to protect it from stomach acid
released from proteins by pancreatic polypeptide
Intrinsic factor needed for absorption
IF-B12 complex absorbed in terminal ileum
stored in liver
What contains vitamin B12?
meat
fish
eggs
dairy
Vitamin b12 excess and deficiency
-
-
Folate
Foods with folic acid
higher requirement in pregnancy
is a coenzyme in methylation reaction
DNA synthesis
synthesis of methionine and homocysteine
s
How are the two clotting factor pathways activated?
intrinsic pathway - contact
extrinsic pathway - FVII coming into contact with tissue factor
initiate cascade results in fibrin clot formation
Which clotting factors are produced in the liver?
I fibrinogen, II prothrombin, IV, V, VI, VII
How can the performance of clotting pathways be measured?
prothrombin time/PT (extrinsic pathway)
international normalised ratio/INR
activated partial thromboplastin time/aPPT (intrinsic pathway)
What might a prolonged PT indicate in the liver? What can cause it outside of the liver?
In liver - deficiency in the synthetic capacity of the liver
Other - DIC, severe GI bleeding, some drugs, Vitamin K deficiency
What are the water soluble vitamins?
Folate
Vitamin C
Vitamin B12
