There are three types of blood cells. They are:(1) Red blood cells (Erythrocytes)\tMost abundant cells in the bloodRed Blood Cells (Erythrocytes)\tAccount for approximately 40 to 45 percent of the blood.\tBiconcave disc which is round and flat, sort of like a shallow bowl.\tDisk diameter of approximately 6.2-8.2 µm.\tThey have a thick rim and a thin sunken center.Functions\tTransport oxygen from the lungs to the cells of the body.\tPick up carbon dioxide from other tissues and unload it in the lungs.(2) White blood cells (Leukocytes)\tThey are the cells that make up the majority of the immune system.\tIt is the part of the body that protects itself against foreign substances and various types of infections.\tThey are made in the bone marrow from multi-potent cells called hematopoietic stem cells.\tThey exist in all parts of the body, including the connective tissue, lymph system, and the bloodstream.Functions\tKills bacteria through the process of phagocytosis.\tThey also release a burst of super oxides that have the ability to kill many bacteria at the same time.(3) Platelets (Thrombocytes)\tNucleus Absent.Platelets (Thrombocytes)\tDo not reproduce.\tSmall fragments of bone marrow cells.\t150,000–400,000 platelets in each microliter of human blood.Functions\tPlatelets are the parts of cells that the body uses for clotting.\tHelps to promote other blood clotting mechanisms. Example: Secrete procoagulants (clotting factors) to promote blood clotting.\tThey secrete vasoconstrictors which constrict blood vessels, causing vascular spasms in broken blood vessels.\tThey secrete chemicals that attract neutrophils and monocytes to sites of inflammation.