Blood and Blood Plasma
Blood is a specialised connective tissue that plays essential roles in transporting oxygen, nutrients, hormones, and waste products, and supporting the immune system. The cellular components of blood—erythrocytes (red blood cells), leukocytes (white blood cells), and platelets—are suspended in a liquid matrix called plasma.
Blood plasma, which makes up 55% of blood volume, is a straw-coloured, translucent liquid. It is primarily composed of water (92%), proteins (albumins, globulins, fibrinogen, and regulatory proteins), electrolytes, nutrients, vitamins, gases, and metabolites. Blood plasma's main functions include:
- Transporting nutrients, hormones, and waste products.
- Facilitating blood clotting through fibrinogen.
- Maintaining the body's osmotic pressure.
- Supporting the immune response through antibodies and other immune factors.
Blood Serum
Blood serum is the liquid part of blood that remains after blood clotting. It is essentially blood plasma without the clotting factors. When blood clots, it forms a gel-like structure (a blood clot) and the remaining liquid is the serum.
Blood serum is composed of:
- Water
- Electrolytes
- Antibodies
- Hormones
- Various proteins
However, unlike blood plasma, blood serum lacks clotting factors, such as fibrinogen. This absence of fibrinogen is what allows serum to remain in a liquid state. Blood serum is a common component of diagnostic tests to analyse electrolytes, proteins, antibodies, and other substances.