THE aorta and its main branches develop from six pairs of branchial arches, which, during the fourth week of pregnancy, conjoin the primitive ventral and dorsal aortas in the embryo.1 In the human being, these six branchial arches become transferred into the permanent major vessels (the aorta and its main branches) during the fifth to the seventh week of embryologic development. Normally, the first and second pairs of arches are absorbed and disappear entirely. The carotid arteries are derived from the third pair of arches. The fourth branchial arch on the left forms the arch of the aorta whereas its . . .