myeloid progenitor cells

Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the (midgestational) aorta-gonad-mesonephros region, through a process known as endothelial-to-hematopoietic transition. In adults, haematopoiesis occurs in the red bone marrow, in the core of most bones. The red bone marrow is derived from the layer of the embryo called the mesoderm. Recent study marks the first global discovery of hematopoietic stem cell (HSC) niches within invertebrate skeletons—overturning the long-held belief that skeletal hematopoiesis is unique to vertebrates, offering a novel evolutionary perspective on stem cell biology. — Wikipedia