Red cells Flashcards
where do all blood cells originate from
bone marrow derived from a cell → multipotent haemopoietic stem cell (HSCs)
recall which cells are then derived from multipotent haemopoetic stem cells
- lymphoid stem cells
- myeloid stem cells (→ RBCs, platelets, granulocytes + monocytes)
define “haemopoisis”
- production of blood cells
- occurs in the bone marrow
haemopoisis of erythrocytes
multipotent lymphoid-myeloid stem cell (HSC) → myeloid stem cell → erythrocyte
-same with granulocytes, monocytes -> macrophages, megakaryocyte
haemopoisis of B cells, T cells + NK cells
multipotent lymphoid-myeloid stem cell (HSC) → lymphoid stem cell → B, T, NK cells
two characteristics of HSCs
1) they can self renew (HSCs not depleted)
2) differentiate to mature progeny (not undifferentiated but can differentiate further?)
define “erythropoiesis”
development of erythrocytes
stages of erythropoiesis
myeloid stem cell → precursor cell (erythroblasts) → erythrocytes
-gradually loses its ribosome so loses its blue colour (Stain)
which growth factor is needed for erythropoiesis?
- erythropoietin (GP synthesised in the kidney)
- stimulated by hypoxia/anaemia → stimulates BM to produce more RBCs (haemostasis)
where is erythropoietin synthesised?
1) 90% in juxatubular interstitial cell (kidney)
2) 10% hepatocytes + interstitial cells
how do RBCs structure help it transport oxygen?
- haemoglobin → 2-alpha + 2-beta chains
- each chain has a haem group held in a chain porphyrin → Fe2+ can bind to 1 O2
- 300 million Hb in each RBC
why is it important to have these two different chains
-interactions between the globing chains for the delivery of O2 to the tissues
what type of haemoglobin in feotuses?
fetal haemoglobin - 2alpha + 2 gamma chains
-facilitates transfer of O2 between mother and foetus
where is iron absorbed?
duodenum
what is non-haem iron?
Fe3+ needs action of reduction substances form absorption ie. vit C
why is iron homeostasis important?
1) excessive iron taxi to liver + heart
2) no mech to excrete iron must be kept 1-2 mg per day
which mechanisms reduce iron levels?
1) bone marrow → RBC recycled
2) liver storage
3) enzymes + myoglobin production
proteins that block release of iron for the stores?
hepcidin
how does hepcidin work?
1) released from liver (hep)
2) targets duodenum + macrophages (ferroportin degraded as hepcidin binds)
which two vitamins are key to produce DNA?
1) vitamin B12
2) folate (folic acid)
what does a deficiency of vitamins B12 and folate affect?
affects all rapidly dividing cells i.e. bone marrow, epithelial surfaces, gonads
-too large cells (can’t divide as not enough DNA + anaemia)
how is vitamin B12 absorbed?
1) combines with intrinsic factor (IF) in stomach
2) B12-IF binds to ileum receptors
reasons for B12 deficiency?
- intake
- IF recreation ie autoimmune disease
- malabsoption
how are RBCs destroyed?
- in reticuloendothelial system
- storage form of iron in macrophages
- transferrin transports Fe in the plasma
