Examine a human peripheral blood smear.

• 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.

Erythrocytes are red blood cells and are recognized by their anuclear, biconcave shape. Since erythrocytes are the most abundant cells in blood, they will predominant in your field of view. The various kinds of leukocytes are all much less numerous. Lymphocytes have spherical nuclei with relatively little cytoplasm.

• 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.

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.