Final answer:
Blood plasma is the extracellular fluid portion of blood, made up mostly of water and containing plasma proteins, solutes, and dissolved gases. It is crucial for transporting substances and maintaining homeostasis. Serum is plasma without the clotting factor fibrinogen.
Step-by-step explanation:
Blood plasma is considered extracellular fluid because it is the liquid component of blood that exists outside the cells. In blood, the extracellular matrix is composed of plasma, while the formed elements consist of erythrocytes (red blood cells), leukocytes (white blood cells), and cell fragments called platelets. Blood plasma itself is over 90% water, with the remainder consisting of plasma proteins such as albumin, globulins, fibrinogen, and other dissolved solutes including glucose, lipids, electrolytes, and dissolved gases.
Blood plasma plays a pivotal role in maintaining the body's pH, osmotic balance, and for protection via antibodies. It is crucial in the transportation of nutrients, gases, and wastes throughout the body, and also in the defense against infections and other threats. It is also involved in the homeostatic regulation of pH, temperature, and other internal conditions.
When the clotting factors are removed from plasma, the resulting liquid is called serum, which is plasma devoid of fibrinogen. Plasma and serum are used in medical diagnostics and research as they carry a plethora of biomarkers and substances crucial to body functions.