What forms the majority of blood?
A) plasma
B) platelets
C) buffy coat
D) leukocytes
The correct answer and explanation is:
The correct answer is A) plasma.
Plasma forms the majority of blood, making up about 55% of its total volume. Plasma is the yellowish liquid portion of blood that remains after the blood cells (red blood cells, white blood cells, and platelets) are removed. It consists primarily of water, which accounts for around 90% of its composition. The remaining 10% includes proteins, electrolytes, nutrients, hormones, gases, and waste products.
Plasma plays several crucial roles in maintaining the overall function of the circulatory system. One of its main functions is transporting nutrients, such as glucose, amino acids, and lipids, to cells throughout the body. It also carries waste products like urea and carbon dioxide to the organs responsible for their removal, such as the kidneys and lungs. Additionally, plasma helps in maintaining blood pressure and volume by balancing the amount of fluid inside the blood vessels.
Plasma proteins, particularly albumin, globulins, and fibrinogen, have significant roles in regulating osmotic pressure, defending against infections, and clotting. Albumin helps maintain the blood’s osmotic balance, preventing the leakage of water into surrounding tissues. Globulins include antibodies that fight infections, while fibrinogen is essential for blood clotting.
The other components listed—platelets, the buffy coat, and leukocytes—are present in much smaller amounts. Platelets are involved in blood clotting and are about 0.5% of blood volume. The buffy coat consists of white blood cells (leukocytes) and platelets, which are critical for immune defense and clotting, but this component is far less abundant than plasma. Therefore, plasma, by volume, constitutes the majority of blood.