The development of arteries.
Reflecting the transition in the process of phylogenesis from the gill circle of the blood circulation to the pulmonary, in a person during ontogenesis, aortic arches are first laid, which are then transformed into the arteries of the pulmonary and bodily circles of the blood circulation. At the 3-week-old embryo truncus arteriosus, leaving the heart, gives rise to two arterial trunks, called the ventral aorta (right and left). The ventral aorta travels upward, then back to the dorsal side of the embryo; here, passing along the sides of the notochord, they are already going in a downward direction and are called dorsal aorta. The dorsal aorta gradually converges with each other and in the middle part of the embryo merge into one unpaired descending aorta. As the embryo of the gill arches develops, the so-called aortic arch, or artery, forms in each of them; these arteries interconnect the ventral and dorsal aorta on each side. Thus, in the area of the gill arches, the ventral (ascending) and dorsal (descending) aortae are interconnected by means of 6 pairs of aortic arches.
In the future, part of the aortic arches and part of the dorsal aorta, especially the right, is reduced, and large primary and main arteries develop from the remaining primary vessels, namely: truncus arteriosus, as noted above, is divided by the frontal septum into the ventral part, from which the pulmonary trunk is formed, and dorsal, turning into ascending aorta. This explains the location of the aorta behind the pulmonary trunk. It should be noted that the latter, due to the current of blood, a pair of aortic arcs, which in lungfish and amphibians gains connection with the lungs, is transformed in humans into two pulmonary arteries – right and left, branches of truncus pulmonalis. At the same time, if the right sixth aortic arch remains only on a small proximal segment, then the left remains all over, forming ductus arteriosus, which connects the pulmonary trunk with the end of the aortic arch, which is important for the circulation of the fetus (see below). The fourth pair of aortic arches remains on both sides all over, but gives rise to different vessels. The left 4th aortic arch together with the left ventral aorta and part of the left dorsal aorta form the aortic arch, arcus aortae.
The proximal segment of the right ventral aorta turns into the brachiocephalic trunk, truncus blachiocephalicus, the right 4th aortic arch – into the beginning of the right subclavian artery extending from the named trunk, a. subclavia dextra. The left subclavian artery grows from the left dorsal aorta caudal to the last aortic arch. Dorsal aorta in the area between the 3rd and 4th aortic arches are obliterated; in addition, the right dorsal aorta is also obliterated from the place of the right subclavian artery to the junction with the left dorsal aorta.