Hematopoiesis Notes PDF

Blood Formation Hematopoiesis, => process o f formation of blood Cells Prof Dr. Siti Balkis Budin blast cell 3 matred cell x Difference between...

Blood Formation Hematopoiesis, => process o f formation of blood Cells Prof Dr. Siti Balkis Budin blast cell 3 matred cell x Difference between leukopoiesis Difference between etythropoiesis 3  Lecture Objectives Name organs responsible for hematopoiesis in the fetus. List the developmental stages of hematopoiesis both prenatally and postnatally. Outline the major steps of post-natal development of blood formed elements (erythropoiesis, granulopoiesis, monocytopoiesis and megakaryopoiesis.  Hemopoiesis or hematopoiesis Negative feedback systems regulate the total number of RBCs and platelets in circulation Abundance of WBC types based of response to invading Loading… pathogens or foreign antigens Red bone marrow primary site Pluripotent stem cells have the ability to develop into many different types of cells Age of animal SITES Site of hematopoiesis OF HEMATOPOIESIS Embryo yolk sac then liver 3rd to 7th month spleen 4th and 5th months marrow cavity - esp. granulocytes and platelets 7th month marrow cavity - erythrocytes Birth mostly bone marrow; spleen and liver when needed Birth to maturity number of active sites in bone marrow decreases but retain ability for hematopoiesis Adult bone marrow of skull, ribs, sternum, vertebral column, pelvis, proximal ends of femurs  Hematopoiesis Hematopoiesis is the process by which perintis immature precursor cells develop into mature blood cells. Loading… A single type of stem cell gives rise to all the mature blood cells in the body. This stem cell is called the -function pluripotential (pluripotent) stem cell.  Stem cells in bone marrow Reproduce themselves Proliferate and differentiate Immature cell in bone marrow called blast cell Cells enter blood stream through large capillary (found irregular sinusoids in liver , marrow) spleen , bone Formed elements do not divide once they leave red bone marrow Exception is lymphocytes  Pluripotent stem cells produce Myeloid stem cells Give rise to red blood cells, platelets, monocytes, neutrophils, eosinophils and basophils Lymphoid stem cells give rise to Lymphocytes Hemopoietic growth factors regulate differentiation and proliferation Erythropoietin – RBCs Thrombopoietin – platelets Colony-stimulating factors (CSFs) and interleukins – WBCs  Bone Marrow Tow types: Red bone marrow, color due to blood and blood forming cells Yellow bone marrow, color due to great number of adipose cells In newborns all bone marrow is red Red bone marrow functions Production of blood cells Destruction of worn-out RBCs Storage (in macrophages) of iron derived from breakdown of hemoglobin  Red Bone Marrow Structure Stroma Meshwork of reticular cells in delicate web of reticular fibers Collagen type I and III Fibronectin, laminin, and hemonectin Interact with cell receptors to bind cells to stroma Hematopoietic cords Hematopoietic cells Sinusoidal capillaries Reinforced by external discontinuous layer of reticular cells and a loose net of reticular fibers Loading…  Blood synthesis Erythropoiesis - The basic process of maturation is synthesis of hemoglobin and formation of enucleated, biconcave erythrocyte Changes during maturation Decrease in cell volume Nucleoli diminish in size until invisible in scope Nuclear diameter decrease and chromatin become denser until nucleus have a pyknotic appearance and finally extruded Decrease number of polyribosomes (basophilia decrease) with increase in hemoglobin (acidophilic) Cell organelles gradually disappear Development of erythrocyte from the first cell of the series until released to blood take 7 days  Erythropoiesis During differentiation nucleus increasing condense (pyknotic) and cytoplasm contains increasing Hb and less RNA Pyknotic nucleus finally extruded, leaving polychromatic erythrocyte (reticulocyte) and remains in marrow for 48 hrs Reticulocyte: no nucleus; cytoplasm still stains somewhat bluish due to presence of remnants of polyribosomes Reticulocyte circulate for 48 hrs and become matured into erythrocyte in spleen and cell reduced in size Erythrocyte mature erythrocyte has no nucleus (in mammals); cytoplasm stains very pink due to lack of ribosomes and presence of high amounts of protein, i.e., hemoglobin  Erytropoiesis: Differentiation of Erythrocytes Proerythroblast First recognizable cell in the series/Large cell with loose chromatin and visible nucleoli/Its cytoplasm is basophilic Basophilic erythroblast Strongly basophilic cytoplasm/Condensed nucleus that has no visible nucleolus Polychromatophilic erythroblast Decrease polyribosoms and increase haemoglobin/ Staining causes several colors to appear Orthochromatophilic erythroblast Nucleus continue to condense/No basophilia is evident and uniformly acidophilic cytoplasm Reticulocyte Nucleus is expelled and engulfed by macrophages/Small number of polyribosoms  Leukopoiesis myeloblast, promylocyte & myelocyte are capable in division Metamylocyte and band cell undergoing maturation Maturation cause reduce in size, development of cytoplasmic granules, increase condensation of nuclear and irregularity of nuclear outlined (fragmentation). Leukocyte precursor not present in circulation  Granulopoiesis Maturation process involves synthesis of protein that are backed in granules First stage results in the development of the azurophilic granules that contain enzymes of lysosomal system Stain with basic dyes In the second stage results in the development of the specific granules several types of proteins are backed in these granules depending on the type of the granulocytes  Maturation of Granulocytes Myeloblast is the most immature recognizable cell in the myeloid series Dispersed chromatin with visible nucleoli Promyelocyte Basophilic cytoplasm and azurophilic granules Give rise to the three known types of granulocytes Myelocyte Specific granules appear and increase Nutrophilic, basophilic and eosinophilic myelocyte Further condensation of nucleus Considerable increase in the their specific granules Neutrophilic granulocyte before maturation passes through an intermediate stage where nucleus has curved rod shape (band cell)  Maturation of Lymphocytes Circulating lymphocytes originate in lymphoid organs Lymphocyte progenitor cells originate in the bone marrow Lymphoblast First identifiable progenitor of lymphoid cells Large cells Polymorphocytes Smaller and more condensed chromatin  Maturation of Monocyte Monoblast Committed progenitor cell that looks like myeloplast Promonocyte Large cell (up to 18 µm in diameter) Basophilic cytoplasm Slightly indented nucleus Chromatin is lacy and visible nucleoli Divide twice leading to monocytes Fine azurophilic granules can be seen in the blood monocyte Mature monocyte stays in circulation Upon tissue damage or infection, monocytes are rapidly recruited to the tissue, where they can differentiate into tissue macrophages or dendritic cells.  Megakryopoiesis Megakryoblast Large ovoid or kidney-shaped nucleus with numerous nucleoli Cytoplasm is homogenous and intensely basophilic Undergo nucleus replication without cell division and increase in cell size Megakaryocytes Irregularly lobulated nucleus Coarse chromatin, no visible nucleoli Cytoplasm contain well developed organelles Become fragmented and produce platelet Thank you for your attention