Examining Blood Cells

First hand investigation 5.3.1
Examining blood cells

Aims:
• To observe prepared slides of human blood and describe the visible cells
• To estimate the size of red blood cells and white blood cells
• To draw scaled diagrams of red and white blood cells

Hypothesis:
On close examination of blood there should be differences in the size and shape of cells, indicating that blood is made up of a number of different components

Material:
• Prepared slides of human blood
• Light microscope
• Graph paper photocopied onto transparency

PART A – MAKING OBSERVATIONS
Method:
1. Draw up a table like table 5.3.2
2. Examine the blood smears provided and use the labelled diagrams provided to try to identify at least three different types of blood cells
3. Record your observations of a red blood cell and as many different white blood cells as you can identify

Results
Type of blood cells shape Other distinguishing features
Red blood cells Circle Light pink/purple; very small
White blood cells Curvy Darker in colour; larger

PART B – ESTIMATING SIZE
Method:
1. Draw up a table like table 5.3.3
2. Place graph paper under low power (10x) and calculate the diameter of your field of view in millimetres (mm). Then multiply this measurement by 1000 to convert it to micrometers)
3. Now calculate what your field of view in high power will be. (if using the 40x lens, your field of view will be one-quarter of what it was under 10x. If using the 100x lens, the field view will be one-tenth)
4. Place the prepared blood slide under low power and focus. Then switch to high power. Move the slide around to find some different types of cells
5. For each type of cell you can identify, estimate:
a) The number of cells of that type that could fit across the diameter of the field of view
b) The size (µm) of one cell of that type
6. Record your estimates in table 5.3.3

Results:
Type of blood cell Diameter of field (µm) Estimated number of cells that could fit...