All blood cells begin as undifferentiated stem cells capable of reproducing themselves. Generations of cells eventually differentiate into cell lines that will mature to produce erythrocytes, leukocytes, and platelets. Stem cells in bone marrow continuously proliferate – usually at a steady state to maintain a constant population of mature blood cells. A disruption in this process can lead to serious illnesses.
As a group, immature cells are large. As they age and mature, they become smaller and change in their reaction to the dyes used to stain them for identification.
Role of the Spleen. Located beneath the diaphragm and behind the stomach, the spleen is an intricate filter that receives 5% of the total blood volume each minute. In the embryo, the spleen is a blood-forming center; it loses this function as the fetus matures.
In the spleen, RBCs and WBCs are “inspected” by specialized WBCs. Old or damaged cells are removed; salvageable cells may be “pitted”, that is, unwanted particles are removed without destroying the cells.Because it is not essential to life, the spleen may be removed (splenectomy) without serious effects.