Red blood cells or erythrocyte in human blood have the longest life span of approximately 100-120 days. After they have compeleted their life span they are removed by the spleen. RBCs or erythrocytes primarily carries oxygen from lungs to all of the living tissues of the body and carries away carbon dioxide. Basophils are a type of white blood cells produced in bone marrow. They are part of our immune system which helps in fighting infections, preventing blood clotting and mediating allergic reactions. Neutrophils are a type of white blood cells, that makes up the largest fraction of blood cells produced by the bone marrow. They act as a first line of defense against infectious organisms that enter our bodies, they have a very short life span, living on average only 8 hours. Platelets also known as thrombocytes are blood cells responsible for blood clotting.