In a centrifuged sample of whole blood, what is the buffy coat?

• A. The bottom layer composed primarily of packed erythrocytes
• B. A layer made primarily of fibrin formed during blood clotting
• C. A thin layer composed mainly of leukocytes and platelets located between the plasma and erythrocytes
• D. The top layer composed primarily of plasma proteins and dissolved solutes only (no formed elements)

Answer: (C)

Verified step by step guidance

1. Understand the composition of whole blood and how it separates when centrifuged: whole blood consists of plasma (the liquid component), erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.
2. Recognize that centrifugation separates blood into layers based on density: the heaviest cells (erythrocytes) settle at the bottom, plasma remains at the top, and the buffy coat forms a thin layer in between.
3. Identify the buffy coat as the layer that contains the less dense formed elements, specifically leukocytes and platelets, which are lighter than erythrocytes but heavier than plasma.
4. Note that the bottom layer is primarily packed erythrocytes, the top layer is plasma, and the buffy coat is the thin middle layer composed mainly of leukocytes and platelets.
5. Conclude that the buffy coat is the thin layer between plasma and erythrocytes, containing white blood cells and platelets, distinguishing it from the other layers.