A&P Cardiovascular System Practice Test

The production of all blood cells comes from hematopoiesis, the process by which hematopoietic stem cells in the bone marrow differentiate into the various blood cell lineages. From these stem cells, two main pathways unfold: one leading to erythroid cells (red blood cells) and some white cells, and another leading to lymphoid cells (lymphocytes). Platelets come from the megakaryocyte lineage, which is also part of hematopoiesis. Because hematopoiesis encompasses the entire formation of red cells, white cells, and platelets, it is the umbrella process that explains how all blood cells are produced. The other terms describe specific lineages within that broader process: erythropoiesis forms red blood cells, lymphopoiesis forms lymphocytes, and thrombopoiesis forms platelets.