Blood is composed of four main elements: Plasma This is the liquid part of blood. It constitutes 55% of its volume. It contains water, proteins, electrolytes, etc.

Red Blood Cells, or Erythrocytes, transport oxygen from the lungs to all tissues in the body and remove carbon dioxide.

Leukocytes, or White Blood Cells: These are cells in the immune system that help defend a person against infection.

Platelets (Thrombocytes): These cell fragments are involved with blood clotting.