Describe the composition, formation and functions of bile.
Bile is produced by hepatocytes, excretion via cannaliculus and biliary tree. It is stored and
concentrated in the gallbladder. Bile contains water, bile acids and bile salts, bile pigments and
electrolytes. Some detail was expected regarding each of these and comment on “Primary bile
acids”, conjugation with taurine and glycine and production of “bile salts”. It was often not
appreciated bacteria in gut produce “secondary” bile acids such as deoxycholate and
lithocholic acid. Additional credit was given for discussing “Unconjugated bilirubin” being
derived from “heme” component of haemoglobin (85%) is carried via albumin to liver for
conjugation via UDP-gluconuryl transferase to “conjugated bilirubin” and that gut bacteria
generate water soluble urobilinogen, enterohepatic recycling and excretion in urine.
The major role of bile is in lipid, cholesterol and lipid soluble vitamin absorption with a minor
role in excretion of bile pigments. It was expected candidates would describe the emulsification
of fat via bile salts and lipid micelle formation to facilitate absorption.