Final answer:
In the blood smear of a healthy adult, roughly 50–70% of leukocytes will be neutrophils, which are characterized by their multi-lobed nucleus and granules that stain light lilac. Different leukocyte counts are typically noted per microliter of blood, aiding in determining the healthiness of the blood sample.
Step-by-step explanation:
Approximately 50–70% of the leukocytes in the blood smear of a healthy adult will be neutrophils. Neutrophils are the most abundant type of leukocytes in the bloodstream, playing a crucial role in the body's immune response. They measure 10–12 µm in diameter, which is larger than erythrocytes, and are part of the body's first line of defense against invading pathogens. A particular characteristic of neutrophils is their multi-lobed nucleus, which becomes more lobed as the cell ages, leading to mature cells being known as polymorphonuclear, or 'polys', while the immature ones are called 'bands'. The granules within neutrophils absorb neutral stains, giving them their name and a light lilac color when observed under a microscope.
When analyzing leukocytes using a blood smear, Figure 18.13 can assist in identifying various leukocytes and understanding if the percentages align with what's expected in a normal sample. Relative leukocyte counts can vary widely across species, and counts are usually expressed per microliter (µl) of blood. These counts are in the thousands, with human counts typically ranging from 4,800 to 10,800 cells per µl.
In identifying different leukocyte types in a systematic manner, creating a simple table to classify leukocytes during the blood examination can be helpful. Such a method, even without a grid system, helps in the assessment of whether a blood smear appears normal or indicates an abnormal condition.