In the body, erythrocytes are red because of the oxidized iron they contain. In stained blood smears, erythrocytes are pink from eosin.
A blood smear is created by spreading a drop of blood thinly over a glass slide, treating the slide with a specific stain, and then examining and analysing the blood cells on the slide. Normal, adult red blood cells lack a nucleus, unlike the majority of other cells, and are uniformly sized (7-8 m in diameter).
They have a dip in the centre rather than a hole since they are round and flattened like donuts (biconcave). After staining the blood smear, the RBCs have a pink colour with a pale core as a result of the haemoglobin they contain. When RBC morphology (appearance) is normal, it is frequently described as normochromic (normal colour) and normocytic (normal size).
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