Blood Formed Elements
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.
By weight, the composition of plasma is about 91.5 % water and 8.5% dissolved solutes. Most of the dissolved solutes are proteins. The remaining solutes are a mixture of nutrients, electrolytes, nitrogenous wastes, respiratory gases, and regulatory compounds.
Also included in the formed elements are five types of white blood cells (WBCs or leukocytes). They are part of the immune system and that helps protect the body from foreign invaders. The WBCs are identified and classified based on their stained appearance.
Three of the WBCs have cytoplasmic granules and are called granulocytes.
The remaining two types of WBCs do not have cytoplasmic granules and are classified as agranulocytes.
The smallest formed element are called platelets (thrombocytes). These are actually cytoplasmic fragments that pinch from large cells called megakaryocytes.
Phospholipids released from platelets help initiate the clotting process.