Hematology and Immunology
Hematology and Immunology

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Hematology and Immunology whole blood - consists of plasma and formed (cellular) elements - 60% to 65% = plasma - 35% to 40% = formed elements = blood cells and platelets - embryologically, blood cells are of mesodermal origin, from ‘blood islands’ in the wall of the embryonic yolk sac - formed elements - blood cells (red cells, white cells, and platelets are produced in red bo ne marrow) = 99% erythrocytes = 99% red blood cells (RBC’s) - in child, all marrow is red (= hematopoietic = blood - forming) - in adult, axial skeleton (cranium, vertebrae, ribs) and flat bones (calvarium and pelvis) have red marrow, but peripheral skeleton has yellow (fatty) marrow - if needed (anemia, hemorrhage), yellow marrow can revert to red marrow red blood cells (RBC’s) = erythrocytes - biconcave disc, diam eter = 7 μm - no nucleus (extruded at maturity) - cytoplasm rich in hemoglobin - transport O 2 from lungs to tissues - 4 O 2 molecules per hemoglobin molecule - transport CO 2 from tissues to lungs - RBC lifespan is approximately 120 days - old RBC’s phagocytosed, mainly in spleen - hematocrit = % of red blood cells in whole blood - normal hematocrit = 35% to 40% - hematocrit generally correla tes with amount of hemoglobin in blood - anemia = reduced number of RBC’s (and/or of hemoglobin per RBC) - some causes: - hemmorhage, acute or chronic - iron deficiency - folic acid (vitamin B9) deficiency - vitamin B12 deficiency - mutation in hemoglobin gene: - example: sickle cell anemia - reduce d hematopoiesis (by disease of or in bone marrow) © blood smear, Wright’s stain, showing scattered platelets, a neutrophil ▼, red blood cells, and a large lymphocyte ► (possibly an NK cell)