GI Flashcards
(54 cards)
Which enzyme converts unconjugated bilirubin to conjugated bilirubin in the liver?
UDP-glucuronyl transferase
where is conjugated bilirubin converted to urobilinogen? (and by what?)
Intestines (GI bacteria)
What are the 6 main functions of the liver?
- Amino acid, carbohydrate and lipid metabolism
- Plasma protein and enzyme synthesis
- Production of bile
- Detoxification
- Storage of proteins, glycogen, vitamin and metals
- Immune functions
+Coagulation
+breaks down RBCs
+Makes hormones
How are bile pigments generated?
from the breakdown of harm group from haemoglobin in macrophages of the RES in the spleen/bone marrow/liver
what are some characteristics of unconjugated bilirubin?
Hydrophobic (water-insoluble)
cannot be excreted or transported in blood unless bound to albumin
What does stercobilin do?
give faeces its brown colour
What is the function of bile salts?
To promote emulsification
What are the lipid soluble vitamins?
Vitamins D,A,K,E
What is the function of secretin?
Stimulates duct cells in the liver to release bicarbonate into the bile and stimulates bile production
What causes PRE-hepatic jaundice?
elevated haemolysis- liver cannot cope with increased levels of unconjugated bilirubin
What causes Gilbert’s Disease?
reduced glucuronyl transferase activity (conjugating enzyme)
Describe achalasia
Failure to relax of the lower oesophageal sphincter leading to a back up of food in the oesophagus
=> regurgitation, malnutrition, eat in secret
Haem iron (red meat) is absorbed straight into the enterocyte in duodenum. How is non-haem iron (white meat, veg etc.) absorbed?
Must first be reduced from ferric (Fe3+) to ferrous (Fe2+) to be absorbed.
Requirs duodenal cytochrome B1, a brush border enzyme, influenced by vitamin C. Then taken into enterocytes via a protein transporter known as divalent metal transporter 1 (DMT1)
What is the fate of iron once absorbed in the enterocyte?
Either storied in the enterocyte (binds to ferritin), RES or RBC or exported into the circulating plasma (through a transporter called ferroportin).
How is iron transported around the body?
Bound to transferrin (plasma protein, synthesised in the liver) which can bind TWO iron atoms. This delivers iron to all tissues (as there are transferrin receptors on all tissue cell surfaces).
What is iron used for in the body?
Bone marrow RBCs RES muscle (in myoglobin) Formation of enzymes
What is ferritin?
protein for storing iron - can be used as marker of iron levels
Acute phase protein (increases in tissue inflammation)
What is the role of hepcidin?
Reduces the levels of iron in the plasma through binding with and degrading ferroportin
=> reducing GI iron absorption (enterocyte)
=>reducing macrophage iron release from RES.
Describe the pathophysiology of haemochromatosis
Homozygous C282Y mutation of HFE gene => reduces synthesis of hepcidin => iron overload in other tissues
=> cirrhosis, diabetes, bronzing, arthritis, restrictive cardiomyopathy…
(bronze diabetes)
What are the true indicators of liver function?
(-)Albumin, (+)prothrombin time + (abnormal)bilirubin
Which is more sensitive for liver disease, AST or ALT?
ALT - L for Liver!
What can you confirm if the ALT/AST ratio is normal?
hepatocellular problem unlikely
When is ALP likely to be raised?
cases of Bile Duct Obstruction (ONLY IF GGT IS RAISED TOO- can show chronic alcohol consumption)
(AND BONE PROBLEMS)
When would bilirubin likely be high?
As a result of hepatocellular or cholestatic disease
