Leukocytes Flashcards
Where is the marginating pool of neutrophils?
Located along the blood vessel walls. The cells adhering to the blood vessel walls are mature and can be quickly released into the circulation when needed. In contrast, the bone marrow pool consists of immature WBCs.
What are the mononuclear cells?
Monocytes and lymphocytes. The term is actually a misnomer since all of the WBCs have only one nucleus. It refers to the fact that these cells do not have segmented nuclei.
Which leukocytes are phagocytic?
Monocytes, neutrophils, eosinophils, and basophils.
Which is the largest WBC on a normal peripheral blood smear?
The monocyte.
What is the predominant WBC from 2 weeks to 4 years of age?
The lymphocyte. Lymphocytes in infants and children often appear reactive so some laboratories do not report reactive (variant) lymphocytes in patients under 2 years of age.
What is the predominant WBC in an adult?
The segmented neutrophil.
What is a normal white count in an adult?
4.5-11.0 x 10^9/L
What is a normal white count in a newborn?
13.0-38.0 x 10^9/L
Which patient population is expected to have the highest WBC?
Newborns.
What are some physiological factors that affect the white count?
Time of day, stress, and exercise.
Describe the improved Neubauer hemacytometer.
The chamber is 3 mm by 3 mm. It is divided into 9 square millimeters. The 4 corner square millimeters are subdivided into 16 squares and the middle square millimeter is subdivided into 25 squares. The hemacytometer has two identical sides and both sides are counted.
What is the formula for determining the number of cells counted in the hemacytometer?
Cells per mm^3 (uL) = cells counted x depth factor x dilution factor x area factor. The depth factor is always 10 since the coverslip sits 0.1 mm above the chamber. The dilution factor is the reciprocal of the dilution used. For example, if a 1:20 dilution is used, the dilution factor is 20. The area factor is the reciprocal of the area counted. For example, if the 5 R squares are counted, the area counted is 1/5 of a mm, so the area factor is 5. If the 4 W squares are counted, the area counted is 4 mm, so the area factor is 1/4.
When counting cells in a hemacytometer, what is the rule when a cell touches a line?
Cells that touch the left and top lines are counted and cells that touch the right and bottom lines are not. This ensures that all cells are counted once and only once.
