Haematology Lecture 2
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What is haemtopoiesis
Production of blood cells
Where do all cells originate from
Stem cells in the bone marrow (haematopoietic stem cells)
What is the formation of red blood cells called
Erythropoiesis
What is formation of platelets called
thrombopoiesis
What is the formation of granulocytes and monocytes called
Myelopoeis
What type of cell can differentiate into any blood cell
-Multi potential hematopoietic stem stell(hemocytoblast) -divides into either common myeloid progenitor or common lymphoid progenitor which then divide further
How is a erythrocyte formed
-made my the process called erythropoietin’s which occurs in the bone marrow Sequence: -haematopoetic stem cell -multipotent progenitor cell -myeloid progenitor cell -proerythrocytes (Normoblast) This occurs in blood marrow -reticulocyte (An immature red blood cell) -erythrocyte This occurs in the blood stream
What happens when a cell which is Going to be an erythrocyte is at the proerythroblast stage (normoblast)
As it starts to become a erythrocytes it gets smaller,the amount of haemoglobin increases,it loses rna and protein synthesis apparatus as it no longer has a nucleus
Where are normoblasts found
Bone marrow
What regulates erythropoiesis
Balance between red blood production and destruction which depends on hormonal controls as well as a adequate supplies of iron,amino acids, and b vitamins
What does too few red blood cells cause
Tissue hypoxia which is detected by type kidney
What does too many red blood cells cause
It increases blood viscosity which can cause The formation of blood cloths
What is hormone erythropoietin(EPO)
• a small 30.4 kD glycoprotein hormone which acts on the early progenitor cells -it is a direct stimulus for erythopoiesis -there is always a small amount in blood to maintain basal rate -kidneys are the primary source however some from the liver
What are effects of epo
➢Rapid maturation of committed marrow cells ➢Increased circulating reticulocyte count in 1–2 days
What are consequences of abusing epo
Can be trapped In smaller vessels causing cloths
Relationship between epo and testosterone
➢Testosterone enhances EPO production, resulting in higher RBC counts in males
What stimulates epo to be produced
Low O2 levels (hypoxia) in blood stimulate kidneys to produce erythropoietin
Causes of hypoxia
-Decreased RBC numbers due to haemorrhage or increased destruction - Insufficient haemoglobin per RBC (e.g., iron deficiency) - Reduced availability of O2 (e.g., high altitudes)
Formation of erythrocytes due to epo sequence
• Low O2 levels in blood stimulate kidneys to produce erythropoietin. • Erythropoietin levels rise in blood. • Erythropoietin and necessary raw materials in blood promote erythropoiesis in red bone marrow. • New erythrocytes enter bloodstream; function about 120 days.
DIETARY REQUIREMENTS FOR ERYTHROPOIESIS
-nutrients such as amino acids,lipids,carbohydrates -iron >free ions are toxic it must be bound to other molecules >stored in cells as ferritin and haemosiderin >transported in blood where bounds to protein called transferrin >vitamin b12(cobalamin) and folic acid necessary for dna synthesis for rapidly dividing cells (developing red blood cells)
What is the protein called that transfers iron around the body
Transferrin which is synthesized in the liver and secreted into the plasma
Daily iron cycle
-Daily loss and absorption of 1mg -most of the iron in the body is contained in haemoglobin
Destruction of erythrocytes
-life span of 100-120 days -old red blood cells become fragile and haemoglobin begins to degenerate -it it recycled in the spleen
Causes of anaemia
➢Blood loss ➢Low RBC production ➢High RBC destruction