Final answer:
The stem cell that precedes the hematopoietic stem cell (HSC) is a pluripotent stem cell, which can differentiate into the HSC. The HSC then undergoes a process called hemopoiesis, dividing into more specialized stem cells such as lymphoid and myeloid stem cells that further differentiate into the formed elements of blood.
Step-by-step explanation:
The stem cell that comes before the hematopoietic stem cell (HSC) is known as a pluripotent stem cell. Pluripotent stem cells have the ability to differentiate into multiple types of cells in the body, including the mesenchymal stem cells that later give rise to hematopoietic stem cells. The HSC, or hemocytoblast, is a specialized type of stem cell that is responsible for generating all the formed elements of blood, through a process called hemopoiesis. Before reaching the HSC stage, totipotent stem cells are at the top of the hierarchy, as they give rise to all cells of the human body, including pluripotent stem cells.
Hematopoiesis begins when the HSC is exposed to hemopoietic growth factors, which trigger the process of division and differentiation. In this process, one daughter cell retains the characteristics of the HSC to ensure the continuation of hemopoiesis, while the other daughter cell differentiates into more specialized stem cells, either lymphoid stem cells or myeloid stem cells. These cells then go through several intermediate stages as precursor cells, or '-blasts', before maturing into the various types of blood cells.