Plasma, red blood cells, white blood cells, platelets
Plasma is mainly water, but also present is sugars, salts, urea,
CO2, proteins, hormones.
Blood is composed of cells and liquid. The liquid is a medium to light clear yellow called plasma. The cells are mainly red blood cells (RBC), a few white blood cells (WBC) and fragments of blood cells called platelets. There are several types of WBC and measuring how many of each can give information on what may be causing someone to be ill.