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Questions and Answers
What is the primary function of erythrocytes in the blood?
What is the primary function of erythrocytes in the blood?
- Transport nutrients
- Combine with O2 and CO2 (correct)
- Produce antibodies
- Regulate body temperature
What is the normal range of RBC count for a healthy adult male?
What is the normal range of RBC count for a healthy adult male?
- 4 - 5 million cells/mm³
- 4.5 - 6 million cells/mm³ (correct)
- 5 - 7 million cells/mm³
- 3 - 4 million cells/mm³
What is used as a diluting solution when counting RBCs?
What is used as a diluting solution when counting RBCs?
- Ethanol
- Distilled water
- Saline solution
- Hayem's solution (correct)
Which of the following materials is NOT required for a manual RBC count?
Which of the following materials is NOT required for a manual RBC count?
What is the appearance of erythrocytes?
What is the appearance of erythrocytes?
What is a common lifespan of erythrocytes in circulation?
What is a common lifespan of erythrocytes in circulation?
What is the main purpose of a RBC count?
What is the main purpose of a RBC count?
What is the depth of the hemocytometer used for RBC counting?
What is the depth of the hemocytometer used for RBC counting?
Which factor might cause errors in RBC counting?
Which factor might cause errors in RBC counting?
Which condition is characterized by a decrease in the number of RBCs below the normal range?
Which condition is characterized by a decrease in the number of RBCs below the normal range?
What can cause physiological polycythemia?
What can cause physiological polycythemia?
What is the total area of each primary square in the counting chamber?
What is the total area of each primary square in the counting chamber?
What is the significance of primary polycythemia?
What is the significance of primary polycythemia?
Which of the following is NOT a source of error in a manual RBC count?
Which of the following is NOT a source of error in a manual RBC count?
How many smaller secondary squares are present in the central primary square?
How many smaller secondary squares are present in the central primary square?
Which primary squares are used for counting white blood cells (WBCs)?
Which primary squares are used for counting white blood cells (WBCs)?
What should you do after drawing blood into the RBC’s pipette?
What should you do after drawing blood into the RBC’s pipette?
For how long should the hemocytometer stand on the bench after loading it with diluted blood?
For how long should the hemocytometer stand on the bench after loading it with diluted blood?
Which magnification lens is used to count RBCs in the hemocytometer?
Which magnification lens is used to count RBCs in the hemocytometer?
How should a drop of diluted blood be introduced into the hemocytometer?
How should a drop of diluted blood be introduced into the hemocytometer?
How many corner squares should be counted for RBCs?
How many corner squares should be counted for RBCs?
What should be included in the count of cells touching the upper and left lines?
What should be included in the count of cells touching the upper and left lines?
What is the dilution factor used in the RBC’s count calculation?
What is the dilution factor used in the RBC’s count calculation?
What is the volume correction factor when the counted volume is 0.02 mm³?
What is the volume correction factor when the counted volume is 0.02 mm³?
How many small squares are counted in the RBC’s count method described?
How many small squares are counted in the RBC’s count method described?
What should the variation between two R squares not exceed?
What should the variation between two R squares not exceed?
How is the counted volume for 5 medium squares calculated?
How is the counted volume for 5 medium squares calculated?
What is the volume of each medium square if using 1/5 mm dimensions?
What is the volume of each medium square if using 1/5 mm dimensions?
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Study Notes
Manual RBC Count Objectives
- Utilize a hematocytometer to count red blood cells (RBCs).
- Estimate circulating RBCs per mm³ of blood.
- Understand physiological and pathological variations in RBC counts.
- Identify factors causing errors in RBC count.
RBC Characteristics
- Total erythrocyte count is expressed as RBCs/mm³ blood.
- Erythrocytes are biconcave, nucleated cells containing hemoglobin, crucial for oxygen transport.
- Average lifespan of RBCs is approximately 120 days.
Normal Range of RBCs
- Healthy adult male: 4.5 - 6 million cells/mm³.
- Healthy adult female: 4 - 5.5 million cells/mm³.
Procedure Overview
- Dilute blood sample with isotonic solution (Hayem's solution) for counting.
- Use a RBC diluting pipette, hemocytometer, and microscope.
Hemocytometer Details
- Consists of two square ruled areas with a depth of 0.1mm.
- Each primary square is divided into 9 secondary squares.
- Central primary square (25 secondary squares) is used for RBC counting.
RBC Counting Procedure
- Draw blood to the 0.5 mark on pipette; complete up to 101 with Hayem's solution.
- Mix and then load diluted blood onto the hemocytometer, allowing it to settle for 3-5 minutes.
- Count RBCs in the central medium square and four corner medium squares using a microscope at 40X magnification.
Calculation of RBC Count
- Total counted cells in the five squares are noted, ensuring variation doesn't exceed 20 cells.
- Correct count formula: Number of RBCs/mm³ = (counted cells in 5 squares) x (diluting factor) x (volume correction factor).
- Example dilution factor: DF = (101 – 1) / 0.5 = 200.
Volume Correction
- For volume correction: Counted volume = (width x length x depth) x number of squares.
- Volume correction factor: VCF = 1 mm³ / counted volume.
Example Calculation
- If 423 RBCs counted in 5 squares:
- RBC count in 1 mm³ = 423 x 200 x 50 = 4,230,000.
Clinical Significance
- RBC count helps assess oxygen delivery to tissues; low counts can reduce oxygen availability.
- Anemia indicates decreased RBC count; polycythemia indicates increased RBC count.
Types of Polycythemia
- Physiological (up to 8 million cells/mm³) can occur due to age or high altitude.
- Pathological:
- Primary: Over 14 million cells/mm³ due to bone marrow malignancies.
- Secondary: Over 8 million cells/mm³ due to respiratory or heart diseases.
Sources of Error in RBC Counting
- Excessive sample flooding in the chamber.
- Missing cells in the count or including artifacts.
Videos for Reference
- Relevant instructional videos can provide additional visual aid to the counting process.
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