Hematology WBC Differential Count & Hematopoiesis

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Questions and Answers

Which type of white blood cell is most prevalent in the blood of adults?

Eosinophils

Lymphocytes

Basophils

Neutrophils (correct)

What is the role of monocytes in the immune system?

To produce antibodies

To directly attack and kill pathogens

To mature into macrophages in tissues (correct)

To initiate the inflammatory response

What characteristic distinguishes band neutrophils from segmented neutrophils?

They are more prominent in chronic infections

They have a completely segmented nucleus

They have a nucleus with more than ½ indentation (correct)

They are the primary response cells in allergic reactions

In a differential count of white blood cells, which is likely to be higher in infants compared to adults?

Lymphocytes Signup and view all the answers

Which statement is true regarding neutrophils?

They have a distinct structure with a segmented nucleus. Signup and view all the answers

What is the main fate of stem cells before they become committed?

They self-renew and repopulate. Signup and view all the answers

What happens to stem cells that remain uncommitted for an extended period?

They undergo apoptosis to prevent overpopulation. Signup and view all the answers

What does the Rule of Three involve in the context of blood test results?

A comparison of red blood cell parameters. Signup and view all the answers

Which progenitor cell type is primarily responsible for producing blood cells excluding lymphocytes?

Common myeloid progenitor cell Signup and view all the answers

During which developmental stage does the liver take over hematopoietic activity?

After several months of fetal development Signup and view all the answers

Which red blood cell characteristics are assessed to identify anomalies?

MCV and MCHC values. Signup and view all the answers

What does MCV represent in a complete blood count?

The average volume of red blood cells in fento liters. Signup and view all the answers

What is true about embryonic hemoglobin produced by primitive erythroblasts?

It includes Gower 1, Gower 2, and Portland hemoglobin. Signup and view all the answers

What characterizes common lymphoid progenitor cells?

They give rise to lymphocytes. Signup and view all the answers

Which factor is crucial to perform before evaluating red blood cell abnormalities?

Ensuring adherence to the Rule of Three. Signup and view all the answers

What is indicated by normocytic and normochromic red blood cells?

Normal red blood cell characteristics. Signup and view all the answers

Which statement correctly describes the difference in impact between myeloid leukemia and lymphoid leukemia?

Myeloid leukemia has a broader impact on multiple cell lines. Signup and view all the answers

What is the initial role of the yolk sac in fetal development regarding blood cells?

It is the source of stem cells for hematopoiesis. Signup and view all the answers

What is the significance of basophilia in immature blood cells?

It signifies the presence of ribosomes and RNA. Signup and view all the answers

Which staining method is used to identify polychromatophilic erythrocytes?

Wright’s stain Signup and view all the answers

What happens to pronormoblasts during their lifecycle?

They can undergo cell mitosis. Signup and view all the answers

What characterizes the staining of mature erythrocytes?

Darker staining due to condensing chromatin. Signup and view all the answers

What ultimately leads to an erythrocyte losing its nucleus?

It reaches the metarubricyte stage. Signup and view all the answers

In relation to cell staining, what makes a cell appear eosinophilic?

An acidic nature of cell content. Signup and view all the answers

Why does the cytoplasm of immature blood cells initially stain light?

Due to the loose chromatin structure. Signup and view all the answers

What is the role of basic stains in cell staining characteristics?

They are attracted to acidic cellular contents. Signup and view all the answers

What should be avoided to ensure the complete separation of RBCs from plasma/serum?

Exposure of reagent to light Signup and view all the answers

What effect can leukocytosis have during blood tests?

It can cause interference in the test results. Signup and view all the answers

What happens if the RBCs are resuspended when not immediately read?

They can rise back into the plasma layer. Signup and view all the answers

Why is it important to position the reader at the edge of the RBCs with plasma?

To ensure an accurate measurement. Signup and view all the answers

What could be a consequence of squeezing the puncture site excessively?

It introduces interstitial fluid into the sample. Signup and view all the answers

Which condition can lead to falsely elevated hematocrit readings?

Carboxyhemoglobin presence Signup and view all the answers

What is the primary purpose of Drabkin’s reagent in blood testing?

To lyse RBCs for hemoglobin release. Signup and view all the answers

What is a recognized source of error when measuring hematocrit levels?

Not accounting for abnormal globulins. Signup and view all the answers

Study Notes

WBC Differential Count

Lymphocytes are the most numerous WBC in infants/children, followed by neutrophils.
In adults, neutrophils are the most abundant, followed by lymphocytes, monocytes, eosinophils, and finally basophils.
Neutrophils have a segmented nucleus in peripheral blood.
Elevated neutrophils indicate acute bacterial infection (early phase).
Band neutrophils have a less segmented nucleus, with indentations more than half the diameter.

Hematopoiesis

Stem cells originate from the mesoblast (yolk sac) and give rise to various blood cells.
Primitive erythroblasts are produced in the yolk sac during fetal development.
Hepatic hematopoiesis takes place in the liver after a few months, replacing the yolk sac function.
Medullary/bone marrow hematopoiesis occurs towards the end of pregnancy and continues into adulthood.

Stem Cell Fates

Self-renewal: Stem cells can repopulate themselves until they become committed to a specific lineage.
Differentiation: Committed stem cells undergo differentiation to produce specific blood cell types.
Apoptosis: Uncommitted stem cells can undergo programmed cell death to prevent overpopulation in the bone marrow.

Progenitor Cells

Common myeloid progenitor cell: Produces all blood cells except lymphocytes.
Common lymphoid progenitor cell: Produces lymphocytes.
Myeloid leukemia affects multiple cell lines, making it more severe.
Lymphoid leukemia affects a single cell line, making it less severe.

Red Blood Cell Development

Primitive erythroblasts carry embryonic hemoglobin (Gower 1, Gower 2, and Portland hemoglobin).
Embryonic hemoglobins have different globin chains compared to adult hemoglobin.
Mature red blood cells lack a nucleus.

Erythroblast Stages

Pronormoblast/Rubriblast: The youngest erythroblast, characterized by a loose chromatin and basophilic cytoplasm.
Basophilic Normoblast/Prorubricyte: Shows intense staining due to condensed chromatin and high ribosome/RNA content in the cytoplasm.
Erythrocytes remain in circulation for 1-3 days before being "polished" into mature erythrocytes.

Polychromatophilic Erythrocytes and Reticulocytes

Polychromatophilic erythrocytes are identified using Wright's stain (Romanowsky stain).
Reticulocytes are identified using supravital stains like New Methylene blue (NMB) or Brilliant Crescent Blue (BCB).
Both cell types exhibit basophilia due to their high content of ribosomes and RNA.

Sources of Errors in Red Blood Cell Count

Exposure of reagents to light
Leukocytosis
Lipemia
Hemolysis-resistant RBCs
Abnormal globulins
Carboxyhemoglobin
Improper resuspension of RBCs
Incorrect use of reading equipment
Hemoglobinopathies
Excessive pressure on the puncture site

Hemoglobin Measurement

Cyanmethemoglobin is a stable compound formed by oxidation and transfer of cyanide molecules to hemoglobin and is measured spectrophotometrically.
Drabkin's reagent is a lysing agent used to release hemoglobin molecules from RBCs; typically stored in amber bottles due to photosensitivity.

Mean Cell Volume (MCV), Mean Cell Hemoglobin (MCH), and Mean Cell Hemoglobin Concentration (MCHC)

MCV is used to estimate red blood cell size and is expressed in fentoliters (fL).
MCHC is often used by physicians to identify different types of anemia.
MCH is equally valuable as MCV and MCHC in identifying different forms of anemia.
The "rule of three" can be used to assess red blood cell size and hemoglobin content. It is recommended to review blood smear results if parameters fall outside the "rule of three" to confirm normocytic and normochromic characteristics.

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Description

This quiz covers essential concepts in hematology, focusing on the white blood cell differential count, hematopoiesis, and the fate of stem cells. You'll explore the roles and characteristics of various white blood cells across different age groups and understand the processes through which blood cells are formed in the body.