MLS Review - Hematology - Fundamentals

MEDICAL LABORATORY SCIENCE REVIEW HEMATOLOGY: FUNDAMENTALS OF HEMATOLOGY OUTLINE • Fundamentals of Hematology o Hematology o Functions Of Hematology Laboratory o History o 3 Categories of Blood Cells o Safety in the Hematology Laboratory o Blood Specimen Collection o Differences Between Capillary and Venous Blood o Hematopoiesis o Prenatal Hematopoeisis o Adult Hematopoetic Tissues o Theories & Regulation of Hematopoiesis o Blood Vessels, Structure & Physiology Legend: ! - Marked as Important/To Memorize FUNDAMENTALS OF HEMATOLOGY HEMATOLOGY • • Discipline that studies development (hematopoiesis) and diseases (anemia, etc.) of blood Includes: o Analyses of concentration (hct, indices, etc.), morphology and function of cells in the blood o Precursors in the bone marrow o Hemostasis and thrombosis ▪ Occurs in blood vessels ▪ Hemostasis - stopping of bleeding with aid of platelets and clotting factors ▪ Thrombosis - clot formation (forming thrombus) ▪ Fibrinolysis - lysis of clot (failure may cause MI) BLOOD COMPOSITION • • • • FUNCTIONS OF HEMATOLOGY LABORATORY • • • • • RED BLOOD CELLS/ ERYTHROCYTES Establish a diagnosis or rule out a diagnosis Confirm a physician’s clinical impression of a possible hematological disorder Detect an unsuspected disorder Monitor the effects of therapy Detect minimal residual disease following therapy HISTORY • • • • Athanasius Kircher (1657) - described “worms” in the blood o Described that blood is comprised of components but and called them “worms” Anton van Leeuwenhoek (1674) - gave an account of RBCs o Father of Microscopy Giulio Bizzozero (late 1800s) - described platelets as “petites plaques” James Homer Wright (1902) - development of Wright stain o Wright stain - foundation of blood cell identification 3 CATEGORIES OF BLOOD CELLS • • • Whole blood – includes erythrocytes, leukocytes, platelets, and plasma Buffy coat – small white layer of cells lying between the packed cell volume and plasma (leukocytes and platelets) Plasma – liquid portion of unclotted blood (hazy & pale yellow) o Consists of fibrin (gives off haziness) o Acquired through anticoagulant-filled tubes Serum – fluid that remains after coagulation (clear and straw colored); blood is allowed to clot and settle Blood constitutes 8% of the body’s tissues Blood cells - form in bone marrow (red marrow in long bones) o Red marrow is gradually replaced by yellow marrow with age Complete Blood Count (CBC) o Provides information on the blood composition o Correlated with diagnosis • • • • • • Anucleate, biconcave, discoid cells filled w/ reddish protein (Hb) Measure 6-8 um in diameter with a zone of pallor (central pallor) that occupies one third of their center Transports oxygen and carbon dioxide Hemoglobin (Hb), Hematocrit, and RBC Indices Anemia - deficiency of healthy RBCs o Caused by inefficient or defective production of RBCs o Increased blood destruction or defective RBCs Polycythemia vera - excessive RBCs that may lead to hyperviscosity (thickening of blood) o Characterized in dengue cases WHITE BLOOD CELLS/ LEUKOCYTES • • • • Loosely related category of cell types dedicated to protecting their host from infection and injury o Infections - caused by microorganisms (bacteria, viruses, parasites, fungi) & other pathogens Related to the immune system in defending the host against infectious/pathogenic agents Immunity/Immune System o Skin/physical barrier - first line of defense o WBCs - second line of defense o Plasma cells, NK cells, macrophages - 3rd line WBC Disorders o Leukopenia - decreased WBC count ▪ Increased susceptibility to infections o Leukocytosis - increased WBC count o Leukemia - uncontrolled proliferation of clone of malignant WBCs; cancer of bone marrow & lymphatic system 1 • • • • • Neutrophils – Bands o Increased: bacterial infection o Decreased: viral infection o Stab cell - unsegmented neutrophils Eosinophils - increased in parasitic infection & allergic rxns Basophils - increased in parasitic infection & allergic rxns Lymphocytes Monocytes - precursors for macrophages SKIN PUNCTURE • • • • The technique of choice to obtain a blood specimen from newborns, pediatric, and geriatric patients Blood obtained from skin puncture is a mixture of blood from venules, arterioles, capillaries, and interstitial, and intracellular fluids Phlebotomist should note that the specimen was obtained by skin puncture because those specimens may generate slightly different test results Collection Sites o Under 1 year of age: Lateral or medial plantar surface of the heel o Children older than 1 year of age and in adults: palmar surface of the distal portion of the third or fourth finger DIFFERENCES BETWEEN CAPILLARY AND VENOUS BLOOD! • PLATELETS/ THROMBOCYTES • • • • • • Maintain blood vessel integrity by initiating vessel wall repairs Main action is to stop bleeding during vessel injusry Hemostasis and thrombosis Adhesion → Secretion → Aggregation o Mode of action of platelets to form thrombus/clot o White thrombus - aggregation of platelets o Red thrombus - fibrin with RBCs SAFETY IN THE HEMATOLOGY LABORATORY • • • • Applicable Safety Practices required by Occupational Safety and Health Administration (OSHA) standard o OSHA ensures healthy and safe working conditions Universal precautions was the original term OSHA’s current terminology is Standard precautions Bloodborne pathogens are pathogenic microorganisms that, when present in human blood, can cause disease. They include, but are not limited to HBV, HCV, HIV. BLOOD SPECIMEN COLLECTION • • HEMATOPOIESIS • • • • • • VENIPUNCTURE • • The superficial veins of antecubital fossa (bend in the elbow) are the most common sites for venipuncture Utilizes syringe or ETS method Capillary blood contains more glucose than venous blood (10-20 mg/dL) Capillary blood contains more leukocytes than venous blood (up to 1000/uL) Capillary blood has lower rbc count and hemoglobin value than venous blood (5%) Capillary blood has a lower platelet count RBC in capillary blood are more fragile than those of venous RBC Continuous regulated process of blood production (renewal, proliferation, differentiation, maturation) Formation, development, and specialization of blood cells Most of hematopoiesis are erythroid Mesoderm o One of the three primary germ layers in the embryo o Give rise to hematopoietic processes Medullary Hematopoiesis o Blood cell production within the bone marrow o Begins in 5th month of gestation and continuous throughout life Extramedullary Hematopoiesis o Blood cell production mainly in the liver and spleen o Occurs when bone marrow cannot meet the body reqs. STAGES OF HEMATOPOIESIS • Prenatal Hematopoiesis o Hematopoietic Stem Cell (HSC) ▪ Totipotent • Most versatile type of stem cells • Present few hours after ovum is fertilized • May develop into any human cell types • Development of embryo to fetus ▪ Pluripotent • Undifferentiated cell producing blood cells of all lineages capable of self-renewal • Present several days after fertilization • Can develop into any cell type • Cannot develop into a fetus 2 ▪ o Multipotent • Undifferentiated cell producing cells of multiple lineages, limited self-renewal (e.g. myeloid SC, lymphoid SC) • Derived from pluripotential stem cell • Limited to specific types of cell to form tissues • • Spleen - active in: ▪ Erythropoiesis - until the end of normal gestation (splenic) ▪ Myelopoiesis - but becomes minimal, by 5th month ▪ Lymphopoiesis - lifetime ▪ Lymph nodes Formation of NRBC’s Granulocytes, Monocytes, lymphocytes, and Megakaryocytes can be observed Detectable Hemoglobins o HbA o HbA2 o HbF MEDULLARY (MYELOID) PHASE • • • • Adult Hematopoiesis o Adult Hematopoietic Tissue ▪ Involved in the proliferation and maturation of blood cells o Blood cell production is restricted primarily in bone marrow ▪ Osteoblasts - bone forming cells ▪ Osteoclast - bone resorbing cells Committed progenitor - undifferentiated cell capable of producing cells of one lineage, colony forming units (CFUs) (e.g. erythroid CFU, CM-CFU) PRENATAL HEMATOPOIESIS • • • • • • • MESOBLASTIC STAGE • • • • • • 19th day of gestation (2nd week of fetal life) formation of blood island in yolk sac (mesodermal extraembryonic layer), aggregation of primitive cells Yolk sac - chief site of mesoblastic Liver & Bone marrow Angioblasts - future blood vessels 9th week of fetal life o Development of primitive erythroblasts (PE) o Produces Hb o Embryonic Forms/Types Of Hemoglobin: ▪ Gower I ▪ Gower II ▪ Portland Occurs intravascularly HEPATIC STAGE • • • • • • • • • 4 to 5th gestational weeks )starts on the 2nd month) Recognizable clusters of developing erythroblasts, granulocytes, and monocytes Lymphoid cells start to appear (exists for lifetime) Reaches to 3rd month Occurs Extravascularly Liver - chief/major site; appear in 3rd month of fetal life Fetal liver reaches its peak in 3rd month of development Thymus – first fully developed organ; major site for T-cell production (Cellular) Kidney and spleen produce B cell production of hepatic stage (Humoral Cell) o Kidney - B cell Starts on the 5th month Occurs in the medulla/inner part of bone marrow o In the developing bone marrow cavity o Red Bone marrow - chief site Development of cells increases at birth Mesenchymal cells migrate into core of the bone and differentiate into skeletal and hematopoietic blood cells. 3 :1 myeloid to erythroid ratio by 21 weeks of gestation By the 6th month, bone marrow is the main site o At the shaft of long bones Hematopoietic phase is apparent Hb A1 - begins to appear and gradually increases in concentration Erythropoietin (EPO), granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), Hb F, Hb A2 SUMMARY OF PRENATAL HEMATOPOIESIS Aka Start End Site Product Mesoblastic Yolk-sac phase 19th day after fertilization 2nd to 4th month after fertilization Yolk-sac, intravascularly Primitive erythroblasts Detectable Gower I, hemoglobin Gower II, Portland Hepatic 4 to 5 weeks after fertilization Peak: 3rd month Liver (primary); thymus, spleen, kidneys (secondary) RBC, and some other blood cells HbA, HbA2, HbF Medullary Myeloid phase 5th to 6th month of development throughout lifetime Bone marrow (primary); Liver and spleen (secondary) Cells of various lineages are seen HbA1, HbA2 ADULT HEMATOPOIETIC TISSUES • Lymphoid Tissues o Primary Lymphoid Tissue ▪ Bone marrow and thymus ▪ Where T and B cells are derived o Secondary Lymphoid Tissue ▪ Lymphoid become competent ▪ Lymphoid cells respond to foreign antigens ▪ Consists of the spleen and lymph nodes and gut associated lymphoid tissue 3 BONE MARROW • • • • • Only site of erythropoiesis, myelopoiesis, thrombopoiesis, & lymphopoiesis o Mother cell → stem cell → lymphoid & myeloid 1st few years of life - a delicate balance exists between developing bone marrow space trabecular bone and the developing infant’s need for blood cells and the liver or spleen remains available because of its hematopoietic capability o Infancy and Early Childhood – all the bones in the body contain primarily red (active) marrow 4th year of life - rate of bone marrow growth exceeds the need for blood cells therefore, active marrow sits are replaced with areas of fatty reserve and fat first develops in the long bones (retrogression) o 5-7th years - adipose tissue become or abundant and begin to occupy the spaces in the long bones previously dominated by active marrow Retrogression - replacing the active marrow by adipocytes (yellow marrow) during development 18th year of life - only active hematopoietic sites are in the pelvis, vertebrae, ribs, scapulae, sternum, skull, and proximal extremities of the long bones • • EXTRAMEDULLARY HEMATOPOIESIS • • • • • • • • • • • • • • • Develops in the embryo by hollowing out of the skeletal bones forming a central cavity o Central Space - due to resorption of cartilage and endosteal bone In this cavity develops a primitive, undifferentiated cell known as a hemocytoblast, or stem cell All blood formed elements ultimately develop from this undifferentiated precursor Contains developing erythroid, myeloid, megakaryotic and leukopoietic progenitors Located in the cavities of the cortical bones o These cavities consists of trabecular bone (honey comb) Full of developing precursor cells in all stages of maturation Released into blood at maturity Only mature cells are released normally First recognizable precursor in each cell line is a blast Red Marrow o Site of blood cell development o Hematopoietically active bone o Comprises approximately 50% of the marrow/cavity space o Sternum, skull, scapula, vertebrae, ribs, pelvic bones and proximal ends of long bones Yellow Marrow o Hematopoietically inactive bone o Mixture of adipose cells, undifferentiated mesenchymal cells, and macrophage o Produces adipocytes → adipose tissue o The remaining 50% of the space is occupied Red and yellow should have approximately equal amounts. • Blood cell production in hematopoietic tissue other than bone marrow Principally occurs in liver and spleen (just like in fetus), lymph nodes and thymus Proteoglycan/ glycosaminoglycans - involved in extramedullary hematopoiesis o Mediates progenitors and binds to stroma Adhesion molecules o Fibronectin o Collagen o Laminin o Hemonectin o Thrombospondin Liver o Second trimester o Major site of blood cell production during hepatic stage o Synthesizing various transport proteins o Storing essential minerals and vitamins that are used in synthesis of DNA and RNA o Conjugating bilirubin from hemoglobin degradation o Transporting bilirubin to the small intestine for eventual excretion (via stool & urine) o Has 2 lobes o Optimal for gathering, transferring and eliminating substances via the bile o Kupffer Cells - macrophages in liver cells ▪ Remove cellular and foreign debris from blood ▪ Protein synthesis o Macrophages - phagocytic cell that removes foreign materials in the blood o Epithelial Cells - allows plasma to have direct access to hepatocytes Spleen o Largest lymphoid organ/structure of lymphoid system o Located on the left side of the abdomen just below the diaphragm and behind the fundus of the stomach o Reticuloendothelial organ o Primary functions: lymphopoiesis, phagocytosis o Graveyard of old blood o “sponge” - absorbs dying cells o Vital but not essential o Indiscriminate filter of the circulating blood o Healthy = 350 ml of blood in SPLEEN. 4 • • Lymph Nodes o Oval structures distributed through the body connected by lymphatic vessels which carry a fluid called lymph ▪ Organs of the lymphatic system located along the lymphatic capillaries o Bean-shaped structures o Act as filters to remove foreign blood contaminats o Extremely important part of body’s infection defense o Superficial (inguinal, axillary, cervical and supratrochkear) or deep (mesenteric and retroperitoneal) o Consists of an outer capsule that forms trabeculae o Provides support for macrophages predominant population of lymphocytes Thymus Gland o Responsible for normal development of some of the lymphocytes o Located in the neck o Maximum development in childhood, atrophies with age • Cytokines o Aka growth factors o Molecules secreted to give signals o Granulocyte Colony-Stimulating Factor (G-CSF) increases production of neutrophils, stimulates granulocyte-macrophage CFU cells o Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) - increases macrophage production, stimulates granulocyte-macrophage CFU cells o Interleukins - stimulate B- and T-cell formation, function together with G-CSF and GM-CSF ▪ Glycoproteins produced by various cells THEORIES & REGULATION OF HEMATOPOIESIS STEM CELL THEORY OF HEMATOPOEISIS • • • • All cells are derived from a pool of stem cells that are selfrenewing Pluripotential & multi potential stem cells give rise to committed stem cells for each cell line Committed stem cells have receptors for specific growth factors Respond to stimulation by division & maturation (precursor cell stages) into end-stage cells BLOOD VESSELS, STRUCTURE & PHYSIOLOGY • • • • • • REGULATION OF HEMATOPOIESIS • • Erythropoietin (EPO) - major regulator of erythropoiesis (RBC production), stimulates erythroid colony forming unit (CFU) cells and proerythroblasts Thrombopoietin (TPO) - increases platelet production, stimulates megakaryocyte CFU cells Arteries - carries oxygenated blood from heart to the body Veins - carries deoxygenated blood from body to heart Arterioles - connects arteries and capillaries Venules - connects veins and capillaries Capillaries - small vessels that connects arterioles and venules where blood gas exchange occur Structure of the Blood Vessels o Tunica Adventitia – Outermost layer o Tunica Media – Middle layer o Tunica Intima – innermost vascular lining ▪ Endothelial Cells (Endothelium) • Involve in clotting process by producing and storing clotting components • Activates platelets, coagulation factors, fibrinolytic system • Has simple squamous epithelium • Highly active metabolically • Involved in clotting process by producing and storing clotting components • Releases substances for all hemostatic, prothrombic, and fibrinolytic processes • 5