Examine a human peripheral blood smear (slide 10) (Fig. 12-3).

• This smear was prepared with polychromatic Wright's stain, which stains both basophilic and acidophilic cellular components.
• This is a typical sample of circulating blood, containing mature erythrocytes and leukocytes.

Identify red blood cells (erythrocytes, Figs. 12-3 and 12-4), the most numerous cells present.

• Note their uniform diameter of about 7 um. Red blood cells can be found in capillaries of most tissues to be examined in this course and their size can provide a measuring standard by which to estimate sizes of other tissue structures.

Why are erythrocytes completely acidophilic and how is their structure adapted to carry out their primary function?

Clinical note: Anemia is the term applied to any significant reduction in the total mass of erythrocytes or in their content of hemoglobin. Iron-deficiency anemia results from having too little iron available for hemoglobin synthesis. The hereditary disease sickle-cell anemia involves a mutation that produces a single amino acid substitution in hemoglobin, which makes the protein crystallize within erythrocytes at low-oxygen tensions. This alters the cells overall shape and can lead to microvascular blockage and various other problems.

Now let's take a look at some white blood cells.