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2.8 perform a first-hand investigation using the light microscope and prepared slides to gather information to estimate the size of red and white blood cells and draw scaled diagrams of each
perform a first-hand investigation using the light microscope and prepared slides to gather information to estimate the size of red and white blood cells and draw scaled diagrams of each
- To perform this investigation, you need to go through the steps for using a light microscope that you learned in the Preliminary course. Revise how to focus the microscope using low power (LP) first and then going to high power (HP).
- To gather information to estimate the size of blood cells, you will have to learn an appropriate technique for estimating. If your school has a grid slide, put it on the stage of the microscope and focus the microscope on low power. If you don’t have a grid slide, use a plastic ruler so you can see the millimetre lines under the microscope.
- Note what size each grid is and when you focus the slide, count the number of grids across the diameter of the field of view. If there is part of one grid, estimate what fraction it is. If the grids are one millimetre apart, you might estimate that the diameter of the LP field of view is 1.5 mm, which is 1500 μm.
- When you go from LP to HP, you see less in the field of view. The diameters of the low and high power fields are inversely proportional to their magnification. If your LP magnifies 100X and the HP magnifies 400X, you will see one quarter of the field that you saw in HP than you saw in LP, so if you saw twenty cells across the diameter under LP, you would see approximately five of the same cells under HP.
- Once you have focused on some red blood cells under LP, estimate the size using the above method, then turn to HP and see if you agree with the first estimate. Draw several cells and draw a scale bar.
- Once you have drawn a few red blood cells, browse over the field looking for some white blood cells. Look for larger cells with clearly defined and stained nuclei and draw several. Draw a scale bar to indicate the size of the cells.
Red blood cells in a blood vessel
Department of Biomedical Engineering and Computational Science (BECS) Centre of Excellence in Computational Complex Systems Research, Helsinki, Finland
Blood cells
Wadsworth Center, New York State Department of Health