Anticoagulant • Agent that prevents or delays blood coagulation
Pathophysiology • Study of how normal processes are altered by disease
Protocols • Formal ideas, plan, or scheme concerning patient care, bench work, administration, or research
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5. Patton M. Advances in microscopy. ADVANCE for Medical Laboratory Professionals 15:21-23, 2003.
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From Hematopoiesis to the Complete Blood Count
Hematopoiesis: The Origin of Cell Development
The Spleen as an Indicator Organ of Hematopoietic Health
The Functions of the Spleen Potential Risks of Splenectomy
The Bone Marrow and the Myeloid: Erythroid Ratio
Alterations in the M:E Ratio
The Role of Stem Cells and Cytokines
The Role of the Laboratory Professional in the Bone Marrow Procedure
Bone Marrow Procedure
Bone Marrow Report
The Complete Blood Count
The Morphological Classification of the Anemias
Calculating Red Cell Indices and Their Role in Sample Integrity
The Value of the Red Cell Distribution Width
The Clinical Approach to Anemias The Value of the Reticulocyte Count
After completing this chapter, the student will be able to:
1. Define the components of hematopoiesis.
2. Describe the organs used for hematopoiesis throughout fetal and adult life.
3. Define the microenvironment and the factors affecting differentiation of the pluripotent stem cell (PSC).
4. Discuss the four functions of the spleen.
5. Differentiate between intramedullary and extramedullary hematopoiesis.
6. Define the myeloid:erythroid ratio.
7. Review the bone marrow procedure, methods and materials, and the technologist's role in ensuring that bone marrow was recovered.
8. List the components of the complete blood count (CBC).
9. Calculate red blood indices.
10. Describe clinical conditions that cause valid shifts in the mean corpuscular volume.
11. Recognize normal and critical values in an automated CBC.
12. Describe ineffective and effective erythro-poiesis.
13. Define the importance of correlation checks in a CBC.
14. Describe the clinical conditions that may produce polychromatophilic cells and elevate the reticulocyte count.
15. Define the morphological classification of anemias.
16. Summarize the symptoms of anemia.
16 PartI • Basic Hematology Principles
HEMATOPOIESIS: THE ORIGIN OF CELL DEVELOPMENT
Hematopoiesis is defined as the production, development, differentiation, and maturation of all blood cells. Within these four functions is cellular machinery that outstrips most high-scale manufacturers in terms of production quotas, customs specifications, and quality of final product. When one considers that the bone marrow is able to produce 3 billion red cells, 1.5 billion white cells, and 2.5 billion platelets per day per body weight,1 the enormity of this task in terms of output is almost incomprehensible. Within the basic bone marrow structure lies the mechanism to
1. constantly supply the peripheral circulation with mature cells.
2. mobilize the bone marrow to increase production if hematological conditions warrant.
3. compensate for decreased hematopoiesis by providing for hematopoietic sites outside of the bone marrow (non-bone marrow sites, the liver and spleen).
The bone marrow is extremely versatile and serves the body well by supplying life-giving cells with a multiplicity of functions. Various organs serve a role in hematopoiesis, and these organs differ from fetal to adult development. The yolk sac, liver, and spleen are the focal organs in fetal development. From 2 weeks until 2 months in fetal life, most erythropoiesis takes place in the fetal yolk sac. This period of development, the mesoblastic period, produces primitive erythroblasts and embryonic hemoglobins (Hgbs) such as Hgb Gower I and Gower II and Hgb Portland. These Hgbs are constructed as tetramers with two alpha chains combined with either epsilon or zeta chains. As embryonic Hgbs, they do not survive into adult life and do not participate in oxygen delivery. During the hepatic period, which continues from 2 through 7 months of fetal life, the liver and spleen take over the hematopoietic role (Fig. 2.1). White cells and megakaryocytes begin to appear in small numbers. The liver serves as an erythroid-producing organ primarily but also gives rise to fetal Hgb, which consists of alpha and gamma chains. The spleen, thymus, and lymph nodes also become hematopoietically active during this stage, producing red cells and lymphocytes; from 7 months until birth, the bone marrow assumes the primary role in hematopoiesis, a role that continues into adult life. Additionally, Hgb A, the majority adult Hgb (alpha 2, beta 2), begins to form. The full complement of Hgb A is not realized until 3 to 6 months postpartum, as gamma chains from hemoglobin F are diminished and beta chains are increased.
Figure 2.1 Marrow formation in fetus (left)versus the adult (right)
Figure 2.1 Marrow formation in fetus (left)versus the adult (right)
Hematopoiesis within the bone marrow is termed intramedullary hematopoiesis. The term extramedullar)/ hematopoiesis describes hematopoiesis outside the bone marrow environment, primarily the liver and spleen. Because these organs play major roles in early fetal hematopoiesis, they retain their hematopoietic memory and capability. The liver and spleen can function as organs of hematopoiesis if needed in adult life. Several circumstances within the bone marrow (infiltration of leukemic cells, tumor, etc.) may diminish the marrow's normal hematopoietic capability and force these organs to once again perform as primary or fetal organs of hematopoiesis. If extramedullary hematopoiesis develops, the liver and spleen become enlarged, a condition known as hepatosplenomegaly. Physical evidence of hepatosplenomegaly will be an individual who looks puffy and protrusive in the left upper abdominal area. Hepatosplenomegaly is always an indicator that hema-tological health is compromised.
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