An adult person has about 5.5 liters of blood, which is made up of:
- The blood plasma, yellowish liquid consisting of water in which many dissolved substances are: mineral salts, nutrients (glucose, amino acids, vitamins), waste substances, hormones, etc.
- The cells blood, which are of three types:
- Red blood cells or red blood cells or erythrocytes: These are the most numerous cells (about 5 million per mm3 of blood). They have no nucleus and contain hemoglobin, an iron-containing red pigment, which carries O2.
- White blood cells or leukocytes: There are several types of white blood cells and they have a defensive function. We have about 6000-7000 white blood cells per mm3 of blood.
- Platelets or thrombocytes: They are not really cells, but fragments of cells. They intervene in blood clotting, preventing blood from being lost in any hemorrhage. We have 200,000 to 300,000 platelets per mm3 of blood.