Enumeration of white blood cell (WBC) count
White blood cell count is an enumeration of white corpuscles or a leucocyte count. The white blood cells (WBCS)or leucocytes are nucleated actively amoeboid, do not contain haemoglobin, and originated purely from extravascular tissue. They are composed of nucleoproteins and varieties of enzymes. Their number is less and their life span is short compared to red blood cells. The WBCs exist in two forms viz. granulocytes and agranulocytes. Granulocytes are further classified as eosinophil, basophil, and neutrophil, while agranulocytes show lymphocytes and monocytes. These varieties possess independent morphological, functional and staining properties. The main function of white blood corpuscles is phagocytosis which is the body’s defence mechanism against foreign particles and invading bacteria. They are also involved in antibody formation in the immunological body defence mechanisms. It also takes part in the process of repair in an area of inflammation.
The basic principle is that the blood is diluted with an acid solution which removes the red cells by haemolysis and also accentuates the nuclei of the white cells; thus the counting of the white cells becomes easy. Blood cell counts can be performed using the hemacytometer.
The white cell count is the number of white cells present in one cubic millimetre of blood. The normal values of white blood cell count vary between 5000 to 10,000 per cubic millimetre or 7-11 thousand cells/µl of blood volume in healthy individuals.
Variation in normal values is observed in diseased states. WBC count increases (leucocytosis) in conditions like pneumonia, leukaemia, meningitis, smallpox etc. while the count decreases (leucopenia) in conditions such as influenza, typhoid, infectious hepatitis etc. Moreover, the count rises in pregnancy and during menstruation. Thus, white blood cell count is useful in diagnosis.
The aim of the experiment is to estimate the white blood cell count of a blood specimen.
Neubauer chamber, WBC pipette, Coverslip, WBC diluting fluid, Needle, spirit, cotton.
- Sterilize the fingertip with a cotton plug soaked in 70% alcohol and let it dry.
- Take a bold prick to have a free flow of blood and draw the blood in a WBC pipette up to the 0.5 mark.
- Dip the WBC pipette in WBC diluting fluid up to the 11 mark and rotate the pipette equally in your hands to mix the solution well by swirling.
- Take the haemocytometer and place it on the flat surface of the workbench. Place the cover slip on the counting chamber.
- Allow a small drop of diluted blood, hanging from the pipette, to sweep into the counting chamber by capillary action. Make sure that there is no air bubble and there is no overfilling beyond the ruled area.
- Leave the counting chamber on the bench for 3 minutes to allow the cells to settle. Observe the cells by placing the counting chamber on the mechanical stage of the microscope.
Focus on one of the corner squares of the counting chamber and count the white cells schematically, starting from the upper left small square of each Square. Repeat the count in all four corners of the chamber. Apply the margin rules i.e. count the cells lying on two adjacent margins, and discard those on the other two margins
No. of cells * Dilution factor * Depth factor / Area count
Dilution factor = 20, Depth factor = 10, Area count = 4
The number of white blood cells present in one µl of the blood specimen is _____
Human Anatomy and Physiology Practical Syllabus
- Study of a compound microscope.
- Microscopic study of epithelial and connective tissue
- Microscopic study of muscular and nervous tissue
- Identification of axial bones
- Identification of appendicular bones
- Introduction to hemocytometry.
- Enumeration of white blood cell (WBC) count
- Enumeration of total red blood corpuscles (RBC) count
- Determination of the bleeding time
- Determination of clotting time
- Estimation of haemoglobin content
- Determination of blood group.
- Determination of erythrocyte sedimentation rate (ESR).
- Determination of heart rate and pulse rate.
- Recording of blood pressure.
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