Ultimately, common myeloid progenitor (CMP) cells which were previously called colony-forming units–granulocyte, erythrocyte, monocyte, megakaryocyte (CFU-GEMM), differentiate into specific lineage-restricted progenitors (Table 10.3). These include the following.
FIGURE 10.18 • Dynamics of hemopoiesis in embryonic and fetal life. During embryonic and fetal life, erythrocytes are formed in several organs. Essentially, three major organs involved in hemopoiesis can be sequentially identified: The yolk sac in the early developmental stages of the embryo; the liver during the second trimester of pregnancy; and the bone marrow during the third trimester. The spleen participates to a very limited degree during the second trimester of pregnancy. At birth, most hemopoiesis occurs in the red bone marrow, as it does in the adult.
 Megakaryocyte/erythrocyte progenitor (MEP) cells: These bipotential stem cells give rise to monopotent megakaryocyte-committed progenitor cells (MKP or CFU-Meg) and other monopotent erythrocyte-committed progenitor cells (ErP or CFU-E) that give rise to the erythrocyte lineage.
 Granulocyte/monocyte progenitor (GMP or CFUGM) cells: Development of the GMP (CFU-GM) cells requires high-level expression of PU.1 transcription factor. These cells then give rise to the neutrophil progenitors (NoP or CFU-G) which differentiate into the neutrophilic lineage; eosinophil progenitors (EoP or CFU-Eo), cells that give rise to eosinophils; basophil/mast cell progenitors (BMCP) that give rise either to basophil progenitor cells (BaP or CFU-Ba) in the bone marrow or MCPs in the gastrointestinal mucosa; and finally monocyte progenitors (MoP or CFU-M) that develop toward monocyte lineages. In addition to the specific lineage progenitors, GMP cells can give rise to dendritic cells (DCs), which are professional antigen-presenting cells. Dendritic cells are discuss in Chapter 14, Lymphatic System.
The common lymphoid progenitor (CLP) cells are capable of diferentiating into T cells, B cells, and natural killer (NK) cells. These multipotential CLP cells have been previously called colony-forming units–lymphoid (CFU-L) The NK cells are thought to be the prototype of T cells; they both possess similar capability to destroy other cells. Lymphocytes are discussed in Chapter 14, Lymphatic System. Dendritic cells can also developed from CLP cells.
Perhaps the easiest way to begin the histologic study of blood cell development is to refer to Figure 10.16 and
TABLE Summary of Features During Maturation of Common Myeloid Progenitor (CMP) Cell10.3 • Large, round nucleuswith 1–2 nucleoli
Smaller, •moreheterochromatic nucleus • Last cell capable of mitosis
Small, deeply stained nucleus
Begins to acquire acidophilia
Acidophilic cytoplasm •with trace of earlier gray
Life span:in blood, 1–120 days
Slightly basophilic •cytoblasm with multiplenucleoli
Round, invaginated •nucleus; may bebinucleate • Enlarges by endomitosis• Polyploid (8–64n) Life span: in marrow, unknowm
Platelets (constantly  produced in marrow)Life span:in blood, 7–10 days • Large, euchromatic spherical nucleus; 3–5 nucleoli • Increased size, 18–24 m • Last cell capable of mitosis • Nucleus is elongate andacquires U shape • Nucleus, 3–5 segmentsor lobes