Template:Gilmour1941 table1

From Embryology
Stages of Erythropoiesis
Stage of development Within embryo or extra-embryonic tissues Within or outside vessels Haemopoietic family Type of erythropoiesls
Jones-Brewer presomite embryo till establishment of circulation (about 2.5 mm) In blood islands in yolk sac, in some of cases in body stalk in the chorion or ' the embryo Intravascular: possibly extravascular in body stalk in a few cases Primitive Megaloblastic
From establishment of circulation (about 2-5 mm) to 9 mm. In general circulation (of embryo, yolk sac and chorion) Intravascular except for continued multiplication of cells in hemorrhages Primitive Megaloblastic
10 mm up to less than 48 mm. In embryo, yolk sac and general circulation Intra- and extra~vascular (marrow first in 57 mm embryo) Partly primitive, partly definitive in general circulation; definitive elsewhere Megaloblastic
48 mm to between 15 and 21 days after birth Intracorporeal in many organs and tissues Extravascular, except sinuses of liver spleen and multiplication of cells in circulation (70 - 160 mm.) Definitive Partly megaloblastic, partly megalo-normoblastic (48-190 mm.); partly megaloblastic, partly normoblastic (190 mm. onwards)
21 days or more after birth Intracorporeal in marrow only Extravascular Definitive Normoblastic