Blood cells are formed in the bone marrow from stems cells. Bone marrow stem cells either create more bone marrow stem cells, or become myeloid stem cells or lymphoid stem cells (Figure 2).
Figure 2 Development of stem cells in the bone marrow
Immature myeloid cells in the bone marrow develop into any of the following cells:
- White blood cells (neutrophils, monocytes, basophils and eosinophils)
- Red blood cells
Immature lymphoid cells give rise to lymphocyte cells which are the white blood cells that help fight infections as part of the immune system.