Development of the right and left pulmonary arteries. A microangiographic study in the mouse.

The developing aortic arches and pulmonary vasculature of 200 mouse embryos (gestational age 11.5-18 days) were directly imaged by stereomicroradiography after perfusion fixation, endothelial staining, and critical point drying. At 11.5-days gestational age, symmetric third, fourth, and sixth aortic arches and proximal portions of the right and left pulmonary arteries were noted. At 12 days, rudimentary pulmonary arteries extended dorsocaudally from the middle portion of the left sixth arch, and there was loss of the dorsal component of the right sixth arch. Semilunar valve anlagen were noted at 12 days, and cusps formed during days 13 and 14. With continued growth, the lungs and pulmonary arteries enlarged and came to occupy a more cephalad position relative to the heart. Stereomicroradiographic techniques permit direct imaging of developing vascular systems in the mouse embryo. Information gained from these whole specimen studies serve to complement serial section and reconstruction studies and offer the potential for evaluating normal and abnormal vascular development.