Embryology Lecture (2) - Development of the Aortic Arches
Vascular Development – Arterial system:
During 4th and 5th weeks of development, aortic arch arises from aortic sac.
During folding:
The primitive aorta is divided into 3 segments:
 Ventral aorta
 First aortic arch
 Dorsal aorta
The 2 ventral aortae fuse to form the heart tube.
The heart tube is connected to the dorsal aorta by the first aortic arch on each side.
The aortic arches terminate in right and left dorsal aortae.
(In the region of the arches the dorsal aortae remain paired, but caudal to this region they fuse to
form a single vessel)
The aortic aches appear in a cranial to caudal sequence gradually.
The aortic sac gives rise to a total of six pairs of arteries. During further development, some
vessels regress completely.
The fifth pair is rudimentary and disappears at a very early stage
Arch I:
Disappears by day 27.
A portion persists to form maxillary artery
Arch II:
Disappears
Remaining portions are hyoid and stapedial arteries
Arch III:
CAROTID ARCH
Persists and becomes a part of carotid arteries.
 Common carotid artery
 Proximal part of internal carotid artery
 External carotid artery
Remainder of internal carotid artery is formed by the
cranial portion of the dorsal aorta
Arch IV:
AORTIC ARCH
Right side: Right subclavian
Left side: Main part of the aortic arch
Arch V:
Disappears
The aortic sac then forms right and left horns, which subsequently give rise to brachiocephalic
artery and proximal segment of aortic arch.
Arch VI:
PULMONARY ARCH
Left:
Ventral part: Left pulmonary artery
Dorsal part: Ductus arteriosus
Right:
Ventral part: Right pulmonary artery
Dorsal part: Disappears
The left recurrent laryngeal nerve recurs on the ductus arteriosus.
Absence of the ductus on the right side allows the right recurrent laryngeal nerve to recur on the
right subclavian artery.
Persistence of the ductus arteriosus and later ligamentum arteriosum is the cause of the left
recurrent laryngeal nerve presence in the thorax, while the right remains in the neck due to
absence of ductus on the right side.
A number of other changes occur:
 Dorsal aorta between entrance of 3rd and 4th arches, known as carotid duct, is
obliterated.
 Right dorsal aorta disappears between origin of the 7th intersegmental artery and
junction with the left dorsal aorta.
So, the Arch of Aorta develops from 3 parts:
 Proximal part: from the left part of the aortic sac
 Middle part: from the left 4th aortic arch
 Distal Part: From the dorsal aorta between the left fourth and 6th arches
Vitelline Arteries
Supplying yolk sac, gradually fuse and form arteries in dorsal mesentery of gut,
 Celiac,
 Superior mesenteric, and
 Inferior mesenteric arteries
These vessels supply derivatives of foregut, midgut, and hindgut respectively.
Umbilical arteries
Paired ventral branches of dorsal aorta
During the 4th week, each artery acquires a secondary connection with dorsal branch of aorta,
common iliac artery, and loses its earliest origin.
After birth the proximal portions of umbilical arteries persist as
 Internal iliac and
 Superior vesical arteries
Distal parts are obliterated to form medial umbilical ligaments.
CLINICAL CORRELATES– Arterial System Defects:
 Under normal conditions the ductus arteriosus is functionally closed through contraction of
its muscular wall shortly after birth to form the ligamentum arteriosum
 A patent ductus arteriosus either may be an isolated abnormality or may accompany other
heart defects
Coarctation of aorta is a narrowing of the aortic lumen distal to the origin of the left
subclavian artery, and above or below the entrance of ductus arteriosus.
o Preductal type: ductus arteriosus persists
o Postductal type: ductus arteriosus is obliterated
Double aortic arch
o Right dorsal aorta persists between origin of 7th intersegmental artery and its junction
with left dorsal aorta.
o A vascular ring surrounds the trachea and esophagus and commonly compresses
these structures, causing difficulties in breathing and swallowing.
Development of the Veins:
In a 4 weeks embryo, three paired veins open into the tubular heart:
 Vitelline veins: returning deoxygenated blood from the yolk sac
 Umbilical veins: bringing oxygenated blood from the placenta.
 Common cardinal veins: returning deoxygenated blood from the body of the
embryo
Vitelline Veins
Cardinal Veins
Pass through the septum transversum
Are responsible to drain the body of the embryo
Drain into the sinus venosus
Cranial part of the embryo is drained by paired anterior
cardinal veins
In relation to the liver developing within the septum
transversum, they divided into:
Pre-hapatic part:
Forms anastomosis around the duodenum, which later gives
rise to the portal vein
Hepatic part:
Interrupted by the liver cords, forms an extensive vascular
network called the hepatic sinusoids
Post-hepatic part:
Left vein disappears
Right vein forms the:
Hepatic veins
Hepatic segment of IVC
Umbilical Veins
Caudal part of the embryo is drained by paired posterior
cardinal veins
The anterior & posterior cardinal veins join to form common
cardinal veins, which drain into the sinus venosus
Anterior Cardinal Veins
Posterior Cardinal Veins
Become connected by an oblique
anastomosis which shunts blood
from left to right
Drain the caudal part of
embryo body, including the
developing mesonephros
This anastomosing channel
becomes the left
brachiocephalic vein
Largely disappear with this
transitory kidneys
Bring oxygenated blood from the placenta
Left anterior cardinal vein
Cranial part: becomes the left
internal jugular vein
Caudal part: degenerates
Initially run on each side of the developing liver
Right anterior cardinal vein
Drain into the sinus venosus
Cranial part:
(cranial to the 7th intersegmental
vein)
becomes the right internal jugular
vein
As the liver grows, the umbilical veins loose their connection
with heart and open into the liver
The right vein disappears by the end of the embryonic period.
The left vein persists
A wide channel, the ductus venosus, appears through the
substance of liver to connect the left umbilical vein with the
inferior vena cava
After birth:
The left umbilical vein obliterate to form the ligamentum teres
of the liver
Ductus venosus obliterate to form ligamentum venosum
Middle part: gives rise to the
right brachiocephalic vein
Caudal part of right anterior
cardinal vein and the right
common cardinal vein form the
superior vena cava
Caudally, the two veins get
connected by an
anastomosing channel that
directs the blood from the
left to the right vein
Gradually the posterior
cardinal veins are replaced
by two new veins:
subcardinal
supracardinal
The adult derivatives of the
posterior cardinal veins are
the:
 Root of the azygos
vein
 Common iliac veins
Development of Superior
Vena Cava
Development of Azygos
Veins
Development of Inferior
Vena Cava
SVC is derived from the:
Caudal part of the right
anterior cardinal vein
Azygos vein is derived from
the:
Cranial part of the right
supracardinal vein
The IVC develops during a
series of changes in the
primordial veins
Right common cardinal vein
Terminal part of the right
posterior cardinal vein
Hemiazygos vein is derived
from the:
Cranial part of the left
supracardinal vein
Composed of:
Hepatic segment derived
from the right vitelline vein
Prerenal segment derived
from the right subcardinal
vein
Renal segment derived from
the subcardinalsupracardinal anastomosis
Postrenal segment derived
from the right supracardinal
vein
Fetal Circulation:
 By the third month of development, all major blood vessels are present and functioning.
 Fetus must have blood flow to placenta.
 Resistance to blood flow is high in the lungs.
Umbilical Circulation:
 Pair of umbilical arteries carries deoxygenated blood & wastes to placenta.
 Umbilical vein carries oxygenated blood and nutrients from the placenta.
Umbilical Vein to Portal Circulation:
 Some blood from the umbilical vein enters the portal circulation allowing the liver to
process nutrients.
 The majority of the blood enters the ductus venosus, a shunt which bypasses the liver
and puts blood into the hepatic veins, then to Inferior vena cava
Foramen Ovale:
 Blood is shunted from right atrium to left atrium, skipping the lungs.
 More than one-third of blood takes this route.
 Is a valve with two flaps that prevent back-flow.
Ductus Arteriousus:
 The blood pumped from the right ventricle enters the pulmonary trunk.
 Most of this blood is shunted into the aortic arch through the ductus arteriousus.
What happens at birth?
 The change from fetal to postnatal circulation happens very quickly.
 Changes are initiated by baby’s first breath.
Foramen ovale
Closes shortly after birth, fuses completely in first year.
Ductus arteriousus
Closes soon after birth, becomes ligamentum arteriousum in about 3 months.
Ductus venosus
Ligamentum venosum
Umbilical arteries
Medial umbilical ligaments
Umbilical vein
Ligamentum teres