Blood Cells
Laboratory Exercise 38
Background
Blood is a type of connective tissue whose cells are suspended in a liquid intercellular
substance. These cells are mainly formed in red bone marrow, and they include red
blood cells (erythrocytes), white blood cells (leukocytes), and some cellular fragments
called platelets (thrombocytes).
Red blood cells transport gases between the body cells and the lungs, white blood
cells defend the body against infections, and platelets play an important role in
stoppage of bleeding (hemostasis).
Materials Needed
Textbook
Compound light microscope
Prepared microscope slides of human blood (Wright’s stain)
Colored pencils
Purpose of the Exercise
Review the characteristics of blood cells, examine them microscopically, and
perform a differential white blood cell count.
Procedure
1. Complete Part A.
2. Refer to figure 38.1 as an aid in identifying the various types of blood cells. Use
the prepared slide of blood and locate each of the following: red blood cell,
neutrophil, eosinophil, basophil, monocyte, lymphocyte, platelet.
3. In Part B, prepare sketches of single blood cells to illustrate each type. Pay
particular attention to relative size, nuclear shape, and color of granules (if
present) in the cytoplasm.
4. A differential white blood cell count is performed to determine the percentage of
each of the various types of white blood cells present in a blood sample. The test
is useful because the relative proportions of white blood cells may change in
particular diseases. Neutrophils, for example, usually increase during bacterial
infections, whereas eosinophils may increase during certain parasitic infections
and allergic reactions.
1
To make a differential white blood cell count, follow these steps:
a. Using high-power magnification, focus on the cells at one end of a prepared
blood slide where the cells are well distributed.
b. Slowly move the blood slide back and forth, following a path that avoids
passing over the same cells twice.
c. Each time you encounter a white blood cell, identify its type and record it on
the table in Part C.
d. Continue searching for and identifying white blood cells until you have
recorded 100 cells in the data table. Because percent means “parts of 100,”
for each type of white blood cell, the total number observed is equal to its
percentage in the blood sample.
5. Complete Part C.
Figure 38.1 Illustrations of the various types of blood cells.
Figure 38.2 A table showing the normal values for a differential white blood cell
count.
Cell Type Normal Value (percent)
Neutrophil 54-62
Lymphocyte 25-33
Monocyte 3-9
Eosinophil 1-3
Basophil <1
2
Part A
Complete the following statements.
1. Mature red blood cells are also called ____erythrocytes________________.
2. The shape of a red blood cell can be described as a
___biconcave______________ disc.
3. The function of red blood cells is ______to transport oxygen and carbon
dioxide______________________________.
4. ___hemoglobin_________________ is the oxygen-carrying substance in a red
blood cell.
5. Red blood cells with high oxygen concentrations are bright red because of the
presence of ____oxyhemoglobin________________.
6. Red blood cells will not reproduce because they lack
__nuclei__________________
when they are mature.
7. White blood cells are also called ____leukocytes________________.
8. White blood cells with granular cytoplasm are called
___granulocytes_________________.
9. White blood cells lacking granular cytoplasm are called
___agranulocytes_______________.
10. Polymorphonuclear leukocyte is another name for a
___neutrophil_________________
with a segmented nucleus.
11. Normally, the most numerous white blood cells are
___neutrophils_________________.
12. White blood cells whose cytoplasmic granules stain red in acid stain are called
____eosinophils________________.
13. _____basophils______________ are normally the least abundant of the white
blood cells.
14. ______monocytes_____________ are the largest of the white blood cells.
15. _______lymphocytes____________ are small agranulocytes that have relatively
large, round nuclei with thin rims of cytoplasm.
16. In red bone marrow, platelets develop from stem cells called
__hemocytoblast_____________.
17. Upon an injury, platelets adhere to ____collagen_________________
found in connective tissue.
18. In the presence of damaged blood vessels, platelets release a substance called
_____hemocytoblast_______________, which causes smooth muscle
contraction.
3
Part B
Sketch a single blood cell of each type in the following spaces. Use colored pencils to
represent the stained colors of the cells. Label any features that can be identified.
Erythrocyte Neutrophil
Lymphocyte Monocyte
4
Eosinophil Basophil
Thrombocyte
5
Part C
Differential White Blood Cell Count Data Table. As you identify white blood cells,
record them on the table by using a tally system, such as IIII II. Place tally marks in
the “Number Observed” column, and total each of the five WBCs when the
differential count is completed. Obtain a total of all five WBCs counted to determine
the percent of each WBC type.
Type of WBC Number Observed Total Percent
Neutrophil
Lymphocyte
Monocyte
Eosinophil
Basophil
Total of column __________
How do the results of your differential white blood cell count compare with the
normal values listed in figure 38.2?
Critical Thinking Application
What is the difference between a differential white blood cell count and a total white
blood cell count?
