Questions and Answers
What is the result of mutations in the genes for the hemoglobin protein?
Hemoglobinopathies
What is the normal range of hematocrit value for males?
37-49%
What is the function of Mean Corpuscular Volume (MCV)?
To measure the average size or volume of the RBC
What is the normal lifespan of RBCs?
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What is the characteristic of reticulocytes?
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What is the normal range of MCV?
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What is the formula for calculating MCV?
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What does MCH indicate?
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What does MCHC measure?
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What is the normal value of MCHC?
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Where does hematopoiesis occur in the third stage of intrauterine development?
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What is the main component of the hemoglobin molecule?
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What is anemia defined as?
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During childhood, what replaces hematopoietic tissues in the long bones?
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What is the manifestation of anemia attributed to?
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How much oxygen binds to 1 gm of Hb?
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What is the predominant type of hemoglobin in the fetus?
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What is one of the compensatory mechanisms to increase oxygen delivery?
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Where is red marrow concentrated in older children and adults?
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What is the percentage of Hemoglobin A at birth?
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What happens when the Hb level is less than 7 gm/dL?
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When does the δ chain synthesis begin?
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What stimulates the differentiation and clonal maturation of erythroid precursors into mature erythrocytes?
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What is the percentage of Hemoglobin F at 6-12 months of age?
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What is the main function of vitamin C in iron absorption?
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Where is iron mainly absorbed in the body?
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What increases iron absorption in the body?
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What is a common manifestation of iron deficiency anemia?
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What diet can decrease iron absorption?
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What is a risk factor for iron deficiency anemia in neonates?
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What is a potential cause of chronic blood loss in infants and children?
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What is a potential symptom of iron deficiency anemia?
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What is the daily requirement of iron in mg/day?
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Which type of anemia is characterized by MCV of 100fl and MCHC of 32-34?
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Which of the following is an example of extracorpuscular defect leading to anemia?
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What is the primary cause of anemia due to inadequate production of RBCs or HB?
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Which of the following is an example of a microcytic hypochromic anemia?
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What is the cause of anemia in chronic renal disease?
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Which of the following is an example of an intrinsic defect leading to anemia?
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What is the cause of anemia in pancytopenia?
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Study Notes
Hematopoiesis
- Hematopoiesis is the process of production of all types of blood cells, including formation, development, and differentiation of blood cells
- Prenatally, hematopoiesis occurs in three stages:
- Yolk sac hematopoiesis (1st 8 weeks)
- Visceral hematopoiesis (8th week to 6th month)
- Myeloid hematopoiesis (6th month onwards)
Hemoglobin
- Hemoglobin molecule is a tetramer made up of 2 pairs of polypeptide chains
- Each chain has a heme group
- Polypeptide chains differ from each other in both the number and sequence of amino acids
- Synthesis is directed by separate genes
Types of Hemoglobin in Humans
- In the embryo (4-8 weeks gestation):
- Gower 1 (ζ2ε2)
- Gower 2 (α2ε2)
- Hemoglobin Portland (ζ2γ2)
- In the fetus:
- Hemoglobin F (α2γ2) predominates during fetal life
- Represents 70% of total Hb at birth
- Decreases to less than 2% after 6-12 months of age
- In adults:
- Hemoglobin A (α2β2)
- Hemoglobin A2 (α2δ2)
Genetics
- Mutations in the genes for the hemoglobin protein result in hemoglobin variants
- Some mutant forms of hemoglobin cause a group of hereditary diseases termed hemoglobinopathies
Role in Disease
- Hemoglobin deficiency can be caused by:
- Decreased amount of hemoglobin molecules
- Decreased ability of each molecule to bind oxygen at the same partial pressure of oxygen
- Hemoglobinopathies may cause both
Blood Indices
- Normal RBCs:
- No nucleus
- Biconcave discs
- Center 1/3 pallor
- Pink cytoplasm (Hb filled)
- Cell size 7-8 µ
- 100-120 days life span
- Reticulocyte (young RBCs):
- No definite nucleus
- Reticulum of RNA
- Deep blue staining
- Light blue cytoplasm
- Cell size about 10 µ
Hematocrit Value (HCT)
- Portion of 100 blood composed of erythrocytes
- Normal males: 37-49%
- Normal females: 36-46%
Mean Corpuscular Volume (MCV)
- Reflects the average size or volume of the RBC
- Expressed in femtoliters (fl)
- Calculated as: MCV = Volume of packed red cells in 1000 ml blood (Hct X 10) / RBC Count (Red cell count) in million in microliter
- Normal value: 70-100 fl
Mean Cell Hemoglobin (MCH)
- Indicates the weight of Hb in the average red cell
Mean Cell Hemoglobin Concentration (MCHC)
- Indicates the concentration of Hb in the average red cell or the ratio of the weight of Hb to the volume in which it is contained
- Expressed in percent
- Normal value: 32-36%
Anemia
- Defined as a reduction in red blood cell mass or blood hemoglobin concentration either singly or in combination
- Compensatory mechanisms:
- Increase in blood flow
- Increase in red cell mass
- Increase oxygen unloading
Classification of Anemia
- Etiological classification:
- A- Inadequate production of RBCs or HB
- B- Anemia due to excessive destruction of RBCs
- C- Anemia due to excessive blood loss
- Morphological classification:
- A- Normocytic normochromic
- B- Microcytic hypochromic
- C- Macrocytic normochromic anemia
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