Leaning Objectives

Question 1

Identify and review the functions and lifespans of the cells of the peripheral blood.

Answer 1

1. RBC: carry oxygen to tissues ~5,000,000
   
   • biconcave, 1/3 pale staining area
   • reticulocytes: young RBC, still contain RNA
2. Platelets: facilitates clotting ~250,000
   
   • formed from large bone precursor: megakaryocytes
3. WBC: fight infections ~5,000
   
   • neutrophils 50%
     
     • PMN, multi-nucleated, potent enzymes
   • lymphocytes 35%
     
     • mononuclear, cannnot differentiate between T and B cells
   • monocytes 6%
   • band neutrophils 6%
   • eosinophils 3%
     
     • allergic reactions, asthma
   • basophils 0.6%
     
     • primary bone marrow proliferative disorder

Question 2

Describe the signs and symptoms of having too many or too few of the major cell types in peripheral blood.

Question 3

Explain what parameters a CBC measures/calculates.

Answer 3

• The values of cell counts, hemoglobin, and hematocrit are in part dependent on the plasma volume
  
  • reduced due to dehydration: cell counts, hgb and hct appear falsely elevated
• WBC differential reports each cell type as a percentage of the total WBC, absolute number of cells in each class per microliter of blood is obtained by multiplying the percentages by the white blood cell count
• absolute values rather than percentages
• normal values are not normal in face of anemias and other diseases

Question 4

Describe the consequences of a loss of hematopoietic stem cells due to toxin or autoimmune attack.

Answer 4

• Problems arise from intrinsically self-renewal properties:

1. genetic damage that results in a proliferative or survival advantage, or an inability to differentiate properly could be replicated and appear in multiple lineages of hematopoietic cells, with the potential for creating a leukemia
2. damage to the small stem cell pool, from immunologic attack, radiation, drugs, or toxins can lead to a failure of the marrow to create blood cells

• Practical implications arising from the biologic behavior of LT-HSC:
  
  1. possible to harvest HSC from the peripheral blood for use in bone marrow transplantion
  2. patient can be “rescued” with additional bone marrow or HSC cells

Question 5

Define anemia, describe its clinical consequences and the ways in which the body attempts to compensate for it.

Question 6

Develop an approach to determining the underlying causes of abnormal CBC results using CBC and reticulocyte count laboratory values.

Question 7

Explain the difference between hemoglobin and hematocrit, and list an approximate value for hematocrit in a typical, healthy person.

Question 8

Define red cell distribution width (RDW), and explain how a low vs. high RDW can help narrow the diagnostic possibilities in the setting of anemia.

Question 9

Identify the different normal cellular components of blood on a smear.

Answer 9

• Peripheral Blood Smear:
  
  • drop of blood swept across glass slide
  • fixed using alcohol
  • Wright-Giemsa stained: negative (DNA/RNA) blue, positive (protein) red
  • Zone of morphology: not too far to one edge or the other of a smear
• Present on a smear:
  
  • Platelets
  • WBC: N>L>Mono>Eos>Bas
  • RBC

Question 10

Explain the meaning and approximate normal ranges for hemoglobin, hematocrit, WBC, RBC, and platelet counts.

Answer 10

• Hemoglobin: normal values of 14-16, depend on male/female
• Hematocrit: ~40%
  
  • percentage of RBC to plasma in a blood sample
• WBC: ~5,000
• RBC: ~5,000,000
  
  • reticulocytes: 1% or ~50,000
• platelets: ~250,000

Question 11

Contrast the normal peripheral blood lifespans of a red blood cell, neutrophil, and platelet.

Answer 11

• Neutrophil (PMN): ~1-4 days
• Lymphocytes (T, B, NK)
  
  • days-years, self-maintaining
• RBC: ~120 days
  
  • reticulocytes: mature for 1 day under normal conditions
• Platelets: ~7 days

Question 12

Describe the properties of stem cells and their role in hematopoiesis.

Answer 12

• Hematopoic Stem Cells (HSC):
  
  • ability to give rise to all hematopoietic cell types
  • self-renewal capacity for entirety of animal’s life
  • HSC live in the bone marrow but can be harvest and given in transplants
• See chart for progession from:
  
  • LT-HSC, ST-HSC, MPP, CMP/CLP, differentiation
• Common Myeloid Progenitors: give rise to Erythrocytes, Platelets, Macrophages, Granulocytes
• Common Lymphoid Progenitors: give rise to Lymphocytes (T-Cells, NK-Cells, B-Cells)
• Bone marrow is predominantly composed of granulocytic and erythroid precursors with the G:E ratio being 2-3:1

Question 13

Describe the basic elements of bone marrow transplantation.

Answer 13

• Stem cells can be harveted from marrow or peripheral blood and transplanted to treat a variety of conditions
• Goal of transplant is to reestablish homatopoiesis and immune function

Types of HSC Bone Marrow Transplants

1. Autologous/Syngeneic: from one’s self
   
   • HSC pop reduced or damaged because of disease or therapy
   • contamination of clonogenic tumor cells or TSCs
   • Increased risk of secondary therapy-rlated malignancy
2. Allogeneic:
   
   • Lack of a donor
   • Graft-versus-host disease: transplant cells attack the hosts cells

Question 14

Explain the general kinetics of red blood cell production and turnover.

Answer 14

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