Procedure Bdifferential White Blood Cell Count

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 or an oil immersion objective, 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 (fig. 38.3).

c. Each time you encounter a white blood cell, identify its type and record it in Part C of the laboratory report.

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.

Complete Part C of the laboratory report.

PROCEDURE A— TYPES OF BLOOD CELLS

1. Review textbook sections on red blood cells, white blood cells, and platelets.

2. Complete Part A of Laboratory Report 38.

3. Refer to textbook figures and figure 38.2 as an aid 2. in identifying the various types of blood cells. Use the prepared slide of blood and locate each of the following:

red blood cell (erythrocyte) white blood cell (leukocyte)

granulocytes neutrophil eosinophil basophil

Figure 38.1 To prepare a blood smear: (a) place a drop of blood about 2 cm from the end of a clean slide; (b) hold a second slide at about a 45° angle to the first one, allowing the blood to spread along its edge; (c) push the second slide over the surface of the first so that it pulls the blood with it; (d) observe the completed blood smear. The ideal smear should be 1)2 inches in length, be evenly distributed, and contain a smooth, feathered edge.

Figure 38.1 To prepare a blood smear: (a) place a drop of blood about 2 cm from the end of a clean slide; (b) hold a second slide at about a 45° angle to the first one, allowing the blood to spread along its edge; (c) push the second slide over the surface of the first so that it pulls the blood with it; (d) observe the completed blood smear. The ideal smear should be 1)2 inches in length, be evenly distributed, and contain a smooth, feathered edge.

Normal Differental Blood Slide

OPTIONAL ACTIVITY

O btain a prepared slide of pathological blood that has been stained with Wright's stain. Perform a differential white blood cell count using this slide and compare the results with the values for normal blood listed in table 38.1.

What differences do you note?_

Table 38.1 Differential White Blood Cell Count

Cell Type

Normal Value (percent)

Neutrophil

Eosinophil

Basophil

Lymphocyte

Monocyte

Human Anatomy Blood

If ut m

Lymphocytes

Monocytes

Platelets

Erythrocytes

Figure 38.3 Move the blood slide back and forth to avoid passing the same cells twice.

Figure 38.3 Move the blood slide back and forth to avoid passing the same cells twice.

Web Quest

What are the functions of the various blood components? What do abnormal amounts indicate? Search these and review blood cell identification at http://www.mhhe.com/biosci/ abio/martinlmwq.mhtml

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Post a comment