Hematology Lec.1 PDF

Haematology lect1 ‫محمد الموسوي‬: ‫الدكتور االستشاري‬ Haemopoiesis: blood cell formation Erythropoiesis :formation of red cells. Erythropoiesis is regulated by the hormone erythropoietin. Normally 90% of the hormone is produced in the peritubular interstitial cells of the kidney an...

Haematology lect1 ‫محمد الموسوي‬: ‫الدكتور االستشاري‬ Haemopoiesis: blood cell formation Erythropoiesis :formation of red cells. Erythropoiesis is regulated by the hormone erythropoietin. Normally 90% of the hormone is produced in the peritubular interstitial cells of the kidney and 10% in the liver. Myelopoiesis : formation of granulocytes and monocytes Thrombopoiesis: formation of platelets Haemopoietic stem and progenitor cells Haemopoiesis starts with a pluripotential stem cell that can self - renew but also give rise to the separate cell lineages. This haemopoietic stem cell is rare, perhaps 1 in every 20 million nucleated cells in bone marrow. On immunological testing it is CD34 + CD38 − Haemopoietic growth factors The haemopoietic growth factors are glycoprotein hormones that regulate the proliferation and differentiation of haemopoietic progenitor cells and the function of mature blood cells. They may act locally at the site where they are produced by cell – cell contact or circulate in plasma. The growth factors may cause cell proliferation but can also stimulate differentiation, maturation, prevent apoptosis Erythropoietin Erythropoiesis is regulated by the hormone erythropoietin. Normally, 90% of the hormone is produced in the peritubular interstitial cells of the kidney and 10% in the liver and elsewhere. There are no preformed stores and the stimulus to erythropoietin production is the oxygen (O 2 ) tension in the tissues of the kidney Reticulocyte : young immature RBC , contains reticular material (RNA) that stains gray –blue -. Reticulums is present in newly released RBC for 1-2 days before the cell reaches its full mature state. Normally , a small number of these cells are found in circulating blood. Reticulocyte count: is used to 1) differentiate anemias caused by bone marrow failure from those caused by hemorrhage 2)hemolysis (destruction of RBCs) 3)to check the effectiveness of treatment in anemia Structure and function of RBC: The mature RBC is a biconcave disc with diameter of 7.5 μm and a circumferential thickness of 2.5 μm. This shape provides a surface area of about 140 μm, 50 % greater than that of a sphere of the same volume, there by providing an efficient transport vehicle for oxygen exchange. The shape also allows for deformability as the erythrocytes move through capillaries of less than half their diameter. An 8 micron cell needs to be able to deform to pass through 3 micron capillaries without fragmentation. This reliability is provided by a cell membrane attached to an underlying cytoskeleton that is adaptable to shape change, elongation & deformation. The RBC membrane : The RBC membrane is a semi-permeable lipid bilayer supported by a protein cytoskeleton. Red blood cell membrane structure : The red blood cell membrane consists of a two-molecule-thick lipid sheath fixed to an intracellular protein network. The constituents of the RBC membrane include: Lipid bilayer (40%) Membrane proteins (52%) Carbohydrate (8%) Haemoglobin Structure Hemoglobin occupies 33% of the RBC volume. - Normal hemoglobin consists of 4 heme groups, which contain a protoporphyrin ring plus iron, and globin, which is a tetramer of 2 pairs of polypeptide chains. - Each globin chain links with heme to form Hb= 4 globin + 4 heme. - The precise order of the amino acids is critical for Hb structure and function. - An adequate amount of globin synthesis is also important. A decreased production in 1 chain results in thalassemia. Hypochromia: refers to the presence of red cells that stain unusually pale Anisocytosis: variation in size of RBC poikilocytosis :. variation in shape of RBC Anemia, General Principles Definition of anemia: Decrease numbers of RBCs , Hb and haematocrit(Hct) below the reference for age and sex ( Hb < 13.5 g/dL (Hct < 40) in men or Hb < 12 g/dL (Hct < 37) in women) Classification of anemia: classification of anemia (based on MCV meancorpuscular volume):