Describe briefly plasma and formed elements of blood.
Plasma is 91% water and 9% protein. It is responsible for transporting nutrients, waste products and hormones. Plasma can be obtained by collecting blood in a lavender top vacutainer tube containing EDTA to prevent clotting, and then centrifuged to remove the formed elements (RBC, WBC, and platelets). The supernatant on top is the blood plasma. Serum is obtained by collecting blood in a red-top vacutainer tube with no additives in it. The blood is allowed to clot (10-30 minutes) and then centrifuged to remove the cells and blood clot. The remaining supernatant is called the serum.