Haemopoiesis+Iron Flashcards
Where are red blood cells produced?
- in bone marrow
- active bone marrow is predominant in infant skeleton but there is more limited distribution in the adult skeleton (pelvis, sternum, ribs, skull, vertebrae).
- bone marrow biopsy is investigation to undertake if there is concern of blood cell count
What factors stimulate megakaryocyte/platelet production/
- thrombopoietin
- GMCSF
What factors stimulate erythroid cell production?
- erythropoietin
- GM-CSF
What factors stimulate granulocyte production?
- G-CSF
- GM-CSF
What factors stimulate lymphocyte production?
- ILs
- TNFs
Which chemical causes a stem cell to become a myeloid progenitor rather than a lymphoid progenitor?
IL-3
What is the RES?
a network in blood and tissues which is part of the immune system containing phagocytic cells:
monocytes macrophages kupffer cells tissue histiocytes microglial cells (in cns)
They perform phagocytosis of damaged dysfunctional cells in spleen and liver mainly.
What is the function of the globin chains in haemoglobin?
protect haem from oxidation, confer solubility, permit variation in oxygen affinity by changing shape
Describe the feedback loop controlling erythropoiesis
- reduced p02 detected in interstitial peritubular kidney cells
- increased erythropoiesis (more EPO produced)
- increased maturation and release of red cells from marrow
- increased haemoglobin in blood
- kidney detects increased p02
- EPO production falls
How is iron excreted from the body?
can’t control excretion but only absorption (lost in nails, hair, skin etc)
How is iron stored in the body?
-ferritin (soluble form)
-haemosiderin (Macrophage iron. Insoluble.
Can stain for this with pearl stain-Blue deposition)
How is jaundice caused?
Body recycles as much haemoglobin as possible from broken down red cells. They are broken down into globin and haem. Globin is a protein, and is converted into constituent amino acids. Haem contains iron which is converted to biliverdin, green. Then, bilirubin in liver. Conjugated in liver by binding to sugar. Excreted into gall duct, bile duct. Changed into stercobillin. Excreted into faeces.
So an excess of red cell destruction causes an excess of bilirubin formation which in turn leads to jaundice
How is iron stored in the liver?
Mainly splenic macrophages and Kupfer cells of the liver
- 95% of the stored iron in liver tissue is found in hepatocytes as ferritin
- Hemosiderin constitutes the remaining 5% and is found predominately in Kupffer cell
What is the difference between haem and non-haem iron?
haem=meat=better (as its in ferrous form)
non-ahem= nuts and grain= fe3+ (ferric form, has to be reduced before absorption)
10-15mg/day iron is needed in the diet
How is iron absorbed?
Stomach acid reduces ferric form to ferrous. Transferrin binds Fe2+ in apical duodenum and upper jejunum. It can be stored as ferritin once inside the enterocyte or transported to the bloodstream. ferrous form can be absorbed across gut lining.
Iron is exported out of the cell by ferropoietin. iron is taken into cells by binding of iron-transferrin complex to transferrin receptor. erythroid cells have highest number of these receptors.
note: fetal enterocytes have lactoferrin receptors as primary source of iron in their diet is maternal breast milk
