Module 5

Platelets (Thrombocytes) are not true cells but are considered as fragments of the big leukocytes termed as Megakaryocytes. However, in chicken there are no megakaryocytes thus platelets in these animals believe to originate in the bone marrow from large mononucleated cells.

Platelets are small sized, pleomorphic cells (sometimes appear as comma shape) and appear as a purple color when observe under the microscope. It is extremely numerous in the circulating blood and once exposed to an injured vessel these cells released several important substances necessary in the prevention of bleeding.

Procedure:

A. Filling of thoma pipette

1. Get fresh, unclotted blood from the animal subject

2. Using a thoma pipette with attached rubber tubing apply gentle suction on the mouthpiece to draw blood exactly to the 0.5 mark of the pipette.

3. Wipe the tip of the pipette then through a steady suction draw the diluting fluid up to 101mark and gently rotate the pipette while filling)

4. Bring the pipette in a horizontal position and place the finger at the tip then remove the rubber tubing

5. Keep the pipette in a horizontal position by holding it between the thumb and middle finger then carefully shake it using a figure of eight for at least 2-3 minutes.

6. Counting of platelets.

7. Clean the hemocytometer and cover glass and make sure these are free from any debrisbefore using and then place the cover glass on top of the counting chamber.

8. Discard at least one third of the contents of the pipette in a clean tissue paper and wipe its tip.

9. Carefully let the fluid flow from the pipette to the space between the chamber and the cover glass to completely fill in the counting chamber.

10. Stand the mixture for about 1-2 minutes to allow cells to settle.

11. Focus under low power (LPO) locate the blood cells in the designated boxes; from the center of the 9 primary squares locate the center (with the 25 small squares)

12. Count the platelets in the entire central ruled area on both chambers. You may reduce the illumination to clearly view the cells.

13. Please remember that you need to avoid duplication in the cell counting, to do so, you may follow this sequence; from upper left corner to right (with 5 squares each row). Then proceed to next row from right to left and so on.