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Answer: The functions of white beads present in the WBC pipette serve as a mixing aids that help in uniformly blending the blood sample with the diluting fluid. This ensures accurate dilution and even distribution of white blood cells (WBCs) before counting them under a microscope using a hemocytometer.
Why Are White Beads Important in a WBC Pipette?
In hematology, accuracy in cell counting is critical. The WBC pipette is specifically designed to count white blood cells using a known dilution. The white bead inside the pipette plays a mechanical role during the mixing process.
Here’s what the white bead does:
- Facilitates proper mixing of blood and diluting fluid when the pipette is shaken.
- Prevents clot formation or cell clumping by keeping the fluid in motion.
- Ensures the uniform suspension of cells, which is crucial for reliable WBC counts.
Without proper mixing, the dilution may be uneven, leading to inaccurate or inconsistent results when viewed in the hemocytometer.
Structure of a WBC Pipette
The WBC pipette is a specialized glass capillary pipette used in manual blood cell counting. Its structure includes:
- A graduated stem, marked at 0.5 and 1.0, for measuring blood volume.
- A bulb that contains the white bead.
- A long, narrow stem is used to expel the diluted sample onto the hemocytometer.
The pipette is used with a Turk’s solution, which stains and lyses red blood cells while preserving WBCs for counting.
How It Works – The Role of the Bead in Action
After drawing 0.5 units of blood and up to 11 units of diluting fluid, the pipette is sealed with the index finger and shaken gently. The white bead moves inside the bulb, ensuring that:
- Every portion of blood mixes thoroughly with the diluting fluid.
- The final suspension is homogeneous.
This movement is especially crucial because white blood cells are fewer in number compared to red blood cells, and even slight inconsistencies in mixing can skew the cell count.
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