erythrocyte that has receptors for factors that stimulate development
Erythropoietin Erythropoietin is the primary erythropoietic factor that cooperates with various other growth factors (e.g., IL-3, IL-6, glucocorticoids, and SCF) involved in the development of erythroid lineage from multipotent progenitors. The burst-forming unit-erythroid (BFU-E) cells start erythropoietin receptor expression and are sensitive to erythropoietin. Subsequent stage, the colony-forming unit-erythroid (CFU-E), expresses maximal erythropoietin receptor density and is completely dependent on erythropoietin for further differentiation. Precursors of red cells, the proerythroblasts and basophilic erythroblasts also express erythropoietin receptor and are therefore affected by it.
Fetal pig The prenatal development of the fetus includes all the tissue and organ development. Within hours of mating, the sperm and egg undergo fertilization in the oviduct and three days later the egg moves into the uterus. The cells begin to specialize by day six, and attach themselves to the uterus lining by day eleven. From fertilization to day 18, the endoderm, ectoderm and mesoderm have been forming inside the embryo, and are completely formed by day 18, the same day the placenta forms. The endoderm transforms into the lungs, trachea, thyroid gland, and digestive tract of the fetus. The ectoderm has a greater role in the development of the fetus. It forms into the skin, nervous system, enamel of the teeth, lining of the intestine, mammary and sweat glands, hoofs, and hair. The mesoderm forms the major organ components that help keep the fetus alive. It forms the muscles and connective tissues of the body, blood vessels and cells, the skeleton, kidneys, adrenal glands, heart, and the reproductive organs. By day 20, most of the major organs are visible, and the last half of gestation focuses greatly on increasing the size of the fetuses.[13]