Matching Pairs Blood Basics Online version Review by Chantica Valverde 1 Leukocytes 2 Erythrocytes 3 PLASMA 4 Hemoglobin 5 Thrombocytes 6 Hematocrit is the percentage of the blood occupied by red blood cells, or erythrocytes White Blood cells, play a key role in the immune system and inflammatory response Platelets, which are important in blood clotting is the liquid part of the blood is iron-based compound that binds with oxygen and transport it to the cells. red blood cells, contain hemoglobin and transport oxygen to the cell