Final answer:
After blood collection, natural coagulation occurs, separating serum from the clot. This process can be enhanced by centrifugation. If anticoagulants are used, plasma rather than serum is obtained without clot formation.
Step-by-step explanation:
During the hour that the blood sample remains in a glass tube, several important processes take place leading up to the harvesting of serum for further analysis. Initially, the blood is collected via capillary action into tubes, where it typically undergoes coagulation. This is where the blood cells and clotting proteins (fibrin threads) form a clot, separating from the liquid component of the blood. Once clotted, the sample is left undisturbed allowing the clot to contract and the serum, which is the liquid portion of blood after coagulation, to naturally separate from the clot. This is often enhanced by centrifugation, which further purifies the serum by spinning down any remaining cells or solid components to the bottom of the tube.
If anticoagulants such as lithium heparin or K2EDTA are present in the collection tubes, they inhibit clot formation and instead of serum, plasma is obtained after centrifugation. Plasma is similar to serum but contains clotting factors since no clot has formed. Depending on the requirements of the subsequent analysis, either serum or plasma is collected as they can provide different types of diagnostic information.