Reticulocytes still contain RNA and form 0.5-2% of circulating erythrocytes
- Pluripotential stem cells → Myeloid and Lymphoid stem cells
- Myeloid stem cells form GEMM colony-forming units → Granulocytes, Erythrocytes, Monocytes and Megakaryocytes
- Lymphoid stem cells go to form T cells and B cells and NK cells.
- Fetus - yolk sac and fetal liver and bone marrow
- Neonate to Adult - Bone marrow
- Understanding the difference between myeloid and lymphoid cell lines is fundamental to make the rest of haematology more simple
- Erythropoiesis is controlled by erythropoietin
- Secreted by the juxtatubular interstitial cells of the renal cortex
- These cells are reduced in number in chronic renal failure
- This leads to a normocytic and normochromic anaemia
- Erythropoietin levels are usually inversely proportional to tissue oxygenation
- Normal levels of EPO are 20 mU per ml which can rise to 20,000 mU per ml due to hypoxia
- The first and rate-limiting step of Haem synthesis occurs within Mitochondria
- This involves the formation of δ-aminolaevulinic acid from Glycine + succinyl CoA.
- The enzyme ALA-synthase requires B6 and is inhibited by haem.
- Thrombopoietin is the major stimulus to platelet production and acts on the megakaryocyte. It is released mostly from the liver but also kidney and skeletal muscle
- G-CSF Granulocyte colony-stimulating factor stimulates the growth of neutrophils
- GM-CSF Granulocyte-Macrophage colony-stimulating factor stimulates the growth of neutrophils eosinophils basophils monocytes and dendritic cells