

Serum is similar to plasma but does not contain any clotting factors (e.g., fibrin). If an anti-clotting agent is not included and blood is allowed to clot before centrifugation, the straw-colored region at the top is now referred to as serum. The tube in which blood is collected has an anti-clotting agent (e.g., heparin or EDTA) in order to prevent blood clotting, which would interfere with proper separation of plasma and formed elements. Occasionally, arterial blood is obtained, which has a bright red color. Generally, venous blood is obtained for this purpose, which has a dark red color. The buffy coat contains the white blood cells and platelets and is less than 1% of total blood volume. Formed blood elements involve erythrocytes, leukocytes and thrombocytes. Blood types Morphology, formation and metabolism of blood elements. After centrifugation, three distinct regions can be observed: (1) plasma, which is ~55% of total blood volume and is the top region, (2) red blood cells (hematocrit or PCV), which make up ~45% of total blood volume and are in the bottom later, and (3) a small, off-white region between plasma and red blood cells that is referred to as the buffy coat. Morphology, formation and metabolism of blood elements 2. To determine hematocrit, whole blood is centrifuged for a few minutes, which leads to the separation of the formed elements from plasma. Hematocrit is also called packed red cell volume (PCV). Hematocrit is the percentage of total blood volume that is occupied by red blood cells. Blood cells and platelets make up approximately 45% of whole blood volume. The formed elements of blood are the red blood cells ( erythrocytes), white blood cells ( leukocytes), and platelets ( thrombocytes). Plasma is straw-colored and makes up approximately 55% of whole blood volume. Plasma is the fluid portion of blood that contains proteins, ions, nutrients, hormones, antibodies, metabolites, enzymes, clotting factors, etc.

Whole blood is composed of plasma (fluid portion of blood) and formed elements (blood cells and platelets). Blood cells and cell fragments that are suspended in the plasma, and include: Erythrocytes (red blood cells): transport oxygen and carbon.
