What is the fluid component of blood called?

The fluid component of blood is known as plasma. Plasma plays a vital role in the circulatory system as it is responsible for transporting various substances throughout the body. It is primarily composed of water, but it also contains proteins, electrolytes, nutrients, hormones, and waste products. Plasma makes up about 55% of total blood volume and is crucial for maintaining blood pressure and volume, facilitating the flow of blood, and aiding in the transport of cells and other materials.

Other components, like serum, are derived from plasma after clotting factors have been removed, whereas hemoglobin is a protein within red blood cells responsible for oxygen transport. Lastly, platelets are cell fragments involved in blood clotting. Each of these components has distinct roles that are essential to the overall function of blood, but only plasma is considered the liquid portion.