PATH Y1 S1: Blood + Haematopoiesis Flashcards
(28 cards)
3 components of blood
liquid:
- plasma (55%): pale, thick, straw-coloured
cellular:
- Buffy coat (<1%): WBC and platelets
- erythrocytes (45%)
where does prenatal haematopoiesis occur?
- yolk sac
- liver
- spleen
- bone marrow
where does postnatal haematopoiesis occur?
- bone marrow in long and flat bones
- sternum, pelvis, ribs, tibia
- lymph nodes
3 nutrients required for haematopoiesis
- iron
- Vit B12
- folic acid (folate)
myeloid vs lymphoid lineage
- myeloid: platelets, RBC, mast cells, granulocytes, agranulocytes
- lymphoid: B + T lymphocytes, NK cells
structure and function of RBCs
- S = biconcave disk, no nucleus (lose it just b4 circulation), no organelles, 64 million Hb molecules
- F = oxygen transport
structure of haemoglobin
- 4 globin (polypeptide) chains - 2 alpha and 2 non-alpha
- each chain has a haem group (so 4 haem groups) which contains Fe > red colour of blood
- bonds are stronger between chains of the same type e.g. alpha-alpha > forms cleavage plate > allows chains to separate for O2 transport
3 types of haemoglobin
- HbA (adult - most common) - 2 alpha and 2 beta
- HbA2 - 2 alpha and 2 delta
- HbF (foetal) - 2 alpha, 2 gamma
iron metabolism
- absorbed > transferrin (transports iron) > most goes to haematopoiesis and some is stored as ferritin in liver + heart
haem iron vs non-haem iron
- haem iron: animal food sources e.g. meat, readily absorbed + bioavailable
- non-haem iron: plant sources > must be hydrolysed in stomach b4 it can be absorbed
why do we not need much iron in our diet?
- most iron is recycled thru plasma iron pool
energy supply of RBCs
- mostly through anaerobic glycolysis (Embden-meyerhof) b/c no organelles
- rest done through hexose monophosphate pathway
- both produce 2,3-DPG > offloading of O2 by Hb
what causes an increased affinity of Hb to O2
- (left shift in graph)
- decreased temp
- less 2,3-DPG
- less acidic
- more CO
- if there is already an oxygen bound to the Hb
what causes a decreased affinity of Hb to O2
- (right shift in graph - think use of oxygen by muscle)
- increased temp
- increased 2,3-DPG
- more acidic
- less CO
compare HbF oxygen dissociation to HbA dissociation
- HbF curve sits to the left of HbA
- Hb has a greater affinity to O2 = advantage for foetus
how is erythropoiesis controlled
- erythropoietin secreted by liver + kidneys, which stimulates differentiation of committed erythroid stem cells into RBC precursors
- mediated by tissue oxygen in kidneys (-ve feedback) so that RBC production can replace RBC loss
how do RBCs get phagocytosed?
- lifetime of 120 days
- then undergoes changes in plasma membrane which signal phagocytosis
- called extravascular haemolysis
- occurs in spleen, liver and bone marrow
how is haemoglobin broken down?
- haem > biliverdin > bilirubin > bile > stercobilin and urobilinogen
- globin > plasma proteins + amino acids
3 types of RBC abnormalities
- membrane: defect in concavity, antigen/antibody reactions > destroyed
- Hb: defect in chains or decreased production
- metabolism: enzyme deficiencies, metabolite abnormalities
anaemia
- low Hb due to:
- decreased production of RBCs/Hb: due to malabsorption, dietary deficiency
- increased destruction of RBCs/Hb: due to haemorrhage, GIT bleeding, drugs
polycythaemia
- increased Hb levels, due to:
- lung, heart, kidney disease
- dehydration (leads to low plasma)
- smoking
- taking anabolic steroids or erythropoietin
how is leucopoiesis controlled?
- cytokines e.g. interleukins (ILs) and colony stimulating factors (CSFs)
- immunological stimuli
leucopenia vs leucocytosis
- penia = deficiency of WBCs
- cytosis/philia = increase in WBCs
structure of platelets and what is the cytokine that stimulates production
- cell fragments of megakaryocyte cytoplasm
- stimulated by thrombopoietin (liver)
