Lecture 1 Hematopoiesis Abdulkarim Aldosari Objectives Define hematopoiesis

Lecture 1 Hematopoiesis, Abdulkarim Aldosari

Objectives § Define hematopoiesis § Describe the origin of hematopoieisis § Define erythropoiesis § List proper cell maturation of the erythrocytic series § Identify three areas of RBC metabolism crucial for normal erythrocyte survival and function § Describe RBC membrane biochemical structure and the consequences of structural membrane defects § Describe Hemoglobin structure, function and synthesis § RBC metabolic pathways

Hematopoiesis § Blood cell formation – production and development § Occurs bone marrow, liver, spleen, lymph nodes, thymus § Bone marrow – sole site of effective hematopoiesis in normal adults § 6 billion cells/kg of body weight per day § 2. 5 billion red cells § 2. 5 billion platelets § 1. 0 billion white cells § Rate adjusted to need, vary from nearly zero to many times the normal § Constant turnover of cells

Origin of Hematopoiesis § Yolk sac > fetal liver/spleen > BM § Primitive erythroblast > migrate to liver (6 wks) – includes other myeloid and lymphoid cells. § At birth the bone cavities are the only site of hematopoietic activity - Starts at 7 months Fig 1 -16, pg. 10

Origin of Hematopoiesis

Origin of Hematopoiesis § Shaft of long bones – until 4 yrs. § Sternum, ribs, pelvis, vertebrae, skull – at 18 -20 yrs. § Other bones have mostly yellow marrow (fat) § At 40 yrs – equal amount of yellow and red marrow

Origin of Hematopoiesis § Takes place in the entire medullary space during infancy and early childhood § Later – occurs in the extravascular part of red marrow § Squeeze through the endothelial lining cells that separates the extravascular marrow from the intravascular compartment- venous sinus § Migrating cells enter the peripheral blood

Hematopoiesis § Steady state of hematopoiesis i. e. production = removal § During increased demand for blood cells § strenuous exercise, high altitudes, smokers § To compensate - Spleen, liver and other tissues can start active hematopoiesis = Extramedullary hematopoiesis § Two pools of cells participate in hematopoietic activity: § Stem cell pool § Bone marrow pool

Hematopoiesis Hematopoietic stem cell pool § Pluripotential - multipotential stem cells (MSCs) § morphologically identical § Continuous self-renewal § Unipotential - committed progenitor cells § Restricted to single cell line § No self-renewal § Lymphoid or myeloid Fig 1 -15, pg. 9

Figure 1 -15

Hematopoiesis Bone marrow pool § proliferating and maturing cells - through the action of cytokines (growth factors) – CSF and IL progenitor cells divide and differentiate § Stored cells for later release to peripheral blood § Cells released to peripheral blood § Storage – WBCS , platelets § Functional – WBCs, platelets, RBCs § Fig 1 -17, pg. 10