Embryonic mouse blood flow and oxygen correlate with early pancreatic differentiation

► Ultrasound-guided in utero intracardiac injection of early mouse embryos is feasible and survivable. ► Early pancreatic development is characterized by sparse, regionalized blood flow. ► Regions of blood flow in the early pancreas correlate with the presence of endocrine cells. ► Embryonic blood flow may be a new regulation point to control tissue proliferation and differentiation.