Briefly outline the production and fate of Red Blood Cells (RBC) (40% of marks).
Describe the breakdown of haemoglobin (Hb) (60% of marks).
The production and fate of red blood cells was well known to most candidates. Marrow
production and its change with development, the sequence of haematogeny and RBC
lifespan were well known. Some candidates failed to mention the role of erythropoietin and
its stimulus by oxygen tension. The breakdown of haemoglobin caused much confusion.
Globin (protein), Fe and haem (porphyrin ring) were all expected to be considered
separately – many candidates omitted one or all. The steps were often confused as was the
nature of transfer in blood, conjugation and release into bile. Conversion to stercobilinogen
or urobilinogen (with reabsorption from the gut and excretion in urine) caused similar confusion. No marks were awarded for discussion of bile salt metabolism from cholesterol
(not haem) or the differences between direct and indirect acting bilirubin.
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