Path - Haem - Exam 2 Flashcards
Describe the structure of the bone marrow (bone anatomy)
- The spongy bone in which haematopoiesis occurs is a reticulin connective tissue network like spiderweb with Mesenchymal Stromal cells, macrophages and other supportive cells to assist haemopoietic cells
- Bone marrow is about 50% empty space and 50% cells
Describe the function of the bone marrow (cellular)
• Normal bone marrow function – production of • red cells • white cells • Platelets
– Requires
• nutrients including iron, B12, B6, folate, amino acids, energy
• supportive cells- stromal cells, cytokines
Normal bone marrow function – CYTOKINES- • Erythroid- includes ERYTHROPOIETIN • Granulocytes- includes G-CSF, GM-CSF • Lymphocytes- Interleukins • Platelets- THROMBOPOIETIN • OTHER – Stromal Cells, Nucleic acids, amino acids etc.
What are cytokine cells and what do they do in haematopoiesis?
Cytokines are small proteins that are involved cell signalling
They are released by macrophages, lymphocytes, endothelial cells, fibroblasts and stromal cells, to affect the behaviour of other cells
In haematopoiesis, the presence of different cytokines dictate which cells are produced i.e. erythropoietin will induce the production of erythrocytes
Describe the differentiation of haemopoietic cells
HSC –> Common Myeloid Progenitor + Common Lymphoid Progenitor
Myeloid –> Megakaryocyte + Erythrocyte + Myeloblast
Megakaryocyte –> Thrombocytes
Erythrocytes –> RBC
Myeloblast –> Basophil, Eosinophil, Neutrophil, Monocyte
Lymphoid –> small lymphocyte –> T cells + B cells
Characteristics of haemopoietic stem cells
Pleuripotent
Displays CD34 on the surface
What are some causes of decreased numbers of RBCs, WBCs and platelets?
Red cells
Marrow failure syndromes, Iron/B12/Folate Deficiencies, Blood loss etc. Renal Failure with reduced production of EPO
– White cells
Viral Infections, Post Chemotherapy, Reduced G- CSF stimulation (rare, inherited)
– Platelets Immune Destruction(ITP), Drugs etc.
What are some causes of increased numbers of RBCs, WBCs and platelets?
Red cells
Hypoxia, Renal Tumours- secretion of EPO
• Whitecells
Myeloproliferative disorder, Secondary: Infection, Inflammation
• Platelets
Essential thrombocythaemia, Inflammation, Infection
What are RBCs unable to do since they lack mitochondria and ribosomes?
incapable of both oxidative phosphorylation and protein synthesis
What is the diameter or a RBC?
7-8um
What are 3 functions of Hb?
Oxygen transport (main), carbon dioxide transport (10% of CO2 from tissue to lungs) and NO transport
What chromosome are the alpha and beta globin genes found on?
16 and 11 respectively
What is haemoglobin switching?
The sequential expression of embryonic, fetal and adult haemoglobin in the developing erythroblast during ontogeny
Describe embryonic switching
Embryo (-9wks)
Gower 1: Zeta2E2
Gower 2: a2E2
Fetus (-9wks to +6wks)
HbF - a2y2
Adult: (6 weeks +)
HbA - a2B2 - 96%
HbA2 - a2&2
HbF - a2y2 -
What makes O2 binding to Hb co-operative?
Binding of each oxygen enhances binding of the next - Bohr effect
What 3 changes can cause a lower O2 affinity?
reduced pH, increased temp and increased 2,3 BPG
What is the advantage of HbF not being able to bind 2,3 BPG effectively?
HbF has a higher affinity than HbA for oxygen. Oxygen is preferentially loaded onto HbF in fetal blood from HbA in the mother’s blood
What are the 2 pathways for glucose metabolism in the RBC?
Glycolysis and Hexose monophosphate shunt (pentose phosphate pathway)
What is the purpose of the reducing power generated by the HMP shunt?
Countering any potential reactive oxygen species that may form from the oxygen carried (OH-, H2O2, HO2, O2-) and the damage to lipids, proteins and enzyme cofactors they would produce. It does this by producing NADP/H and Glutathione
What is methaemoglobin?
An oxidised form of Hb with Fe3+ instead of Fe2+. It cannot carry oxygen and precipitates out.
What is the enzyme converting glucose 6P to 6P gluconate?
glucose 6P dehydrogenase
How does HMP shunt prevent oxidative stress?
Production of large amounts of NADPH that prevents oxidative stress by maintaining glutathione levels. Glutathione is a reducing agent that converts peroxide to water and prevents oxidative damage.
In patients with G6PD deficiency, what oxidising agents may trigger oxidative stress?
medications, broadbeans and infections
Why might the anaemia from pyruvate kinase deficiency (most common glycolytic enzyme deficiency) not be as symptomatic as expected?
PK def causes loss of membrane pump function and loss of membrane plasticity, leading to usually shaped cells that are destroyed in the spleen. There is also an increase in 2,3-DPG, shifting the haemoglobin curve to the right, allowing greater offloading of oxygen. As a result, only appear slightly anaemic.