The hematologic System is broadly classified into three subcategories, erythrocytes, leukocytes, and platelets. Erythrocytes (red blood cells) are most abundant, occupying approximately 48% of blood volume in men and 42% in women. Red blood cells are primarily responsible for tissue oxygenation due to an organic compound known as hemoglobin. Leukocytes (white blood cells) defend the body against organisms that cause infection and also remove debris, including dead or injured host cells of all kinds. Leukocytes act primarily in the tissues but are transported in the circulation. Leukocytes are then subdivided into either granulocytes, agranulocytes, phagocytes, or immunocytes. Platelets (thrombocytes) are not cells, but disk-shaped cytoplasmic fragments essential for blood coagulation and control bleeding. They lack a nucleus and cannot divide.
![Picture](/uploads/1/7/3/1/17317476/5213147.png)
This is an image of the different types of White blood cells.
PubMed:http://www.ncbi.nlm.nih.gov/pubmed/24654249
Sources: Fishbein, Morris. The New Illustrated Medical and Health Encyclopedia.
New York: H. S. Stuttman, 1970. Print.
New York: H. S. Stuttman, 1970. Print.