the Arterial System of the Embryonic Circulation

• The arterial portion of the embryonic circulation consists of the ventral and dorsal aortae and the aortic arches
• Although the dorsal aortae remain separate in the region of the aortic arches, they fuse from at the level of the fourth thoracic segment to the fourth lumbar segment of the spine to form a midline dorsal aorta in the fourth week.
• Three sets of branches are formed from the midline dorsal aorta:

  • ventral branches supplying the gastrointestinal tract and its derivatives
  • lateral branches supplying the suprarenal glands, kidneys and gonads
  • dorsolateral intersegmental branches, called intersegmental arteries, which give rise to part of the vasculature of the head, neck, body wall, spine and limbs.
• The aortic arches also give rise to the ductus arteriosus
• The ductus arteriosus connects the pulmonary artery to the (descending) aorta, allowing the blood flow to circumvent the pulmonary system throughout fetal life.