Arterial development

In the third week of embryonic development, two ventral aortas branch off from the arterial trunk. Six pairs of aortic arches connect the ventral aortas with the initial sections of the right and left dorsal aortas. Aortic arches I, II and V are soon reduced, so the main role in the formation of the arteries of the head, neck and thoracic cavity is played by the III, IV and VI aortic arches, as well as sections of the right and left ventral and dorsal aortas. The anterior section of each ventral aorta (from the I to the III aortic arch) is transformed into the external carotid artery. Every third aortic arch and the anterior section of the dorsal aorta are transformed into the internal carotid artery. The section of the dorsal aorta between the III and IV aortic arches is reduced, and the corresponding section of the ventral aorta is transformed into the common carotid artery. The left IV arch becomes the arch of the definitive aorta, which connects the ascending and descending parts of the aorta. The right dorsal aorta (posterior to the IV right aortic arch) is reduced, the IV right aortic arch becomes the proximal portion of the subclavian artery. The portion of the right ventral aorta (between the right III and IV aortic arches), from which it branches off, turns into the short brachiocephalic trunk; its branches are thus the right carotid and right subclavian arteries. The left subclavian artery develops not from the aortic arches, but from one of the intersegmental dorsal arteries - a branch of the left dorsal aorta. As a result, the brachiocephalic trunk, left common carotid and left subclavian arteries branch off from the definitive arch of the aorta.

The sixth pair of aortic arches after the division of the arterial trunk into the ascending aorta and the pulmonary trunk become the pulmonary arteries. The right VI arch loses its connection with the dorsal aorta, and its distal portion is completely reduced. The left VI aortic arch retains its connection with the left dorsal aorta in the form of a wide arterial (Botallo's) duct, through which blood from the pulmonary trunk flows into the aorta in the fetus; after birth, the duct becomes empty, and the arterial ligament remains in its place.

The intersegmental dorsal arteries undergo a number of changes. Each of these arteries is divided into a dorsal and ventral branch. In the neck and head region, their dorsal branches form the vertebral artery, and closer to the front (cranial) - the basilar artery and its branches. In the trunk region, the intersegmental arteries transform into the posterior intercostal arteries, which supply the body walls. The ventral branches form the left subclavian artery and the distal portion of the right subclavian artery.

The segmentality of the lateral and ventral arteries of the embryonic body is disrupted during development. The paired diaphragmatic, renal, adrenal and testicular (ovarian) arteries are formed from the lateral segmental arteries. Unpaired arteries that supply blood to the abdominal organs develop from the ventral segmental arteries: the celiac trunk, the superior and inferior mesenteric arteries. The caudally located ventral segmental arteries transform into the right and left umbilical arteries. The axial artery of the lower limb departs from the beginning of each of them. Subsequently, the axial artery undergoes reverse development, and in an adult it is represented by a thin peroneal artery and a very thin artery accompanying the sciatic nerve. As the pelvic organs and especially the lower limbs form, the iliac arteries (common, external and internal) reach significant development. The umbilical artery becomes a branch of the internal iliac, and the external iliac, as the main arterial trunk, continues to the lower limb into the femoral, popliteal, anterior and posterior tibial arteries.

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