During the end of the 3rd week of development, vasculogenesis occurs from the posterolaterally located paraxial mesoderm. Vessels form between developing somites and join with the dorsal aorta to form intersegmental arteries. Around the 7th week, the internal thoracic artery is formed when the longitudinal branches of the intersegmental arteries from the dorsal aorta become linked via longitudinal anastomosing channels and lose their connection to the aorta (Schoenwolf et al. 2020).