| The formed elements are cells, cell remnants, and cell fragments in the blood. Red blood cells (= RBCs or erythrocytes) make up more than 95% of the formed elements. Because they lack a nucleus and organelles, most RBCs in the blood stream are not fully functional cells. Instead, they serve as temporary, hemoglobin-filled containers that transport oxygen throughout the body. The white blood cells (= WBCs or leukocytes) are also part of the formed elements. They help protect the body from foreign invaders. Because they are almost clear, the WBCs are difficult to see under a microscope. When stained, however, their nuclear and cytoplasmic characteristics become more apparent. Based on their stained appearance, five types of WBCs can be indentified. Neutrophils, eosinophils, basophils all have granules in their cytoplasm and are thus classified as granulocytes. Two other types of WBCs, the monocytes and lymphocytes, do not have cytoplasmic granules. These cells are classified as agranulocytes. Yet another type of formed element are the platelets (= thrombocytes). These are actually cytoplasmic fragments that pinch from large cells called megakaryocytes. Phospholipids released from platelets help initiate the clotting process. |
