Transcript 12-Aortic Arches

The Aortic Arches
Dr. Zeenat Zaidi
Embryonic Blood Vessels
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By the beginning of the 4th
week, an extensive network of
blood vessels is formed
throughout the embryonic
body
The heart begins to beat on
21st or 22nd day, and blood
begins to circulate.
This makes the CVS to be the
first system in the body to
reach the functional state
The embryonic heartbeat can
be detected ultrasonographically during the 5th
week
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The main embryonic
vessels are the paired
dorsal aortae, which
receive blood from
the heart and
distribute it to body
tissues
The dorsal aortae fuse
caudally during the
fourth week, forming
a single median
vessel, the descending
aorta.
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The descending
aorta gives the
following branches:
 Lateral segmental
 Ventral segmental
 Dorsal intersegmental
The caudal end of the
descending aorta
becomes the median
sacral artery
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Lateral Segmental
Arteries:
 Supply the:
 Diaphragm
 Kidneys
 Adrenal glands
 Gonads
 These vessels become
the phrenic, renal,
middle suprarenal, and
gonadal arteries of the
adult.
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Ventral Segmental
Arteries:
 Supply the:
 Yolk sac (Vitelline
arteries)
 Allantois (Umbilical
arteries)
 Embryonic part of
placenta (Chorionic
arteries)
Vitelline arteries:
 Supply the yolk sac and
the primitive gut
 Three major arteries
remain as the:
 Celiac trunk (artery of
foregut)
 Superior mesenteric
artery (artery of midgut)
 Inferior mesenteric
artery (artery of
hindgut).
Umbilical arteries:
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Pass through the connecting
stalk in close association with
the allantois
Become continuous with the
chorionic blood vessels.
Carry poorly oxygented blood
to the placenta
Derivatives:
 Proximal parts: persist as
the superior vesical arteries,
which supply the urinary
bladder
 Distal parts: obliterate after
birth and become the
median umbilical ligaments
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Dorsal intersegmental
arteries:
 Somatic branches
 About thirty or more pairs arise
at serial segmental levels, run
between the somites
 Supply the body wall, limbs,
brain and spinal cord.
Derivatives:
 In cervical region: join to form the
vertebral artery. The 7th pair
contributes to the subclavian arteries.
 In thoracic region: become the
posterior intercostal arteries
 In abdominal region: become the
lumbar arteries. The 5th pair remains
as the common iliac artery
 In sacral region: form the lateral sacral
arteries
Aortic Arches
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The aortic arches are a series of
paired arterial channels encircling
the embryonic pharynx
They:
 Develop in the 4th week
 Supply the developing
pharyngeal arches
 Arise from the aortic sac
 Run dorsally, embedded in the
mesenchyme of the pharyngeal
arches and
 Terminate in the right and left
dorsal aortae
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Develop in a craniocaudal
sequence
There are potentially six pairs,
but the fifth pair is poorly
developed and disappears soon
after formation
Not all the 6 pairs present at the
same time. By the time the 6th
aortic arches are formed, the 1st
& 2nd have disappeared
In the region of aortic arches, the
dorsal aortae remain paired, but
caudal to this region they fuse to
form a single median vessel
Aortic
--sac
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During week 6 to 8, the primitive aortic arch
pattern is transformed into the adult arterial
arrangement of carotid, subclavian, and
pulmonary arteries
Derivatives of Aortic Arches
First Pair
Largely disappear
 Dorsal part persists
as the maxillary
arteries which
supply the ear, teeth
and muscles of the
eyes and face
 May give rise to the
external carotid
artery
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The first arch is obliterated before
the 6th arch is formed
Second Pair
Largely disappear
 Dorsal part persists
as the hyoid and
stapedial arteries
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Third Pair
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Proximal part:
forms the
common
carotid arteries
Distal part:
joins the dorsal
aortae to form
the internal
carotid arteries
Fifth Pair
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Disappears
completely
with NO
vascular
derivatives
The fate of 4 & 6th pairs of aortic
arches differs on the right and left
side
Fourth Pair
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RIGHT:
Becomes the
proximal part of
the right
subclavian artery
LEFT: Forms
part of the arch
of aorta
Arch of Aorta
Derived as:
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Proximal segment
from aortic sac
Middle segment from
the left 4th aortic arch
Distal segment from
the left dorsal aorta
Subclavian Artery
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The right subclavian
artery formed from the:
 Right 4th aortic arch
 Right dorsal aorta &
 Right 7th
intersegmental artery
The left subclavian
artery formed from the
left 7th intersegmental
artery
Sixth Pair
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RIGHT:
• Proximal part: persists as the
proximal part of the right
pulmonary artery
• Distal part: degenerates
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LEFT:
• Proximal part: persists as the
proximal part of the left
pulmonary artery
• Distal part: forms ductus
arteriosus, a shunt between
pulmonary artery and dorsal
aorta
Changes in the original aortic arch system
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Obliteration of:
1. Most of the 1st & 2nd arches
2. 5th arches completely
3. Distal part of the right sixth
arch
4. The segment of both aortae
lying between the 3rd & 4th
arches
5. The segment of right aorta
lying between the 7th
intersegmental artery & the
fused dorsal aortae
Relation of recurrent laryngeal nerves
to the aortic arches
Anomalies of the
Aortic Arches
Coarctation of Aorta
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Characterized by narrowing of aorta
More common in males
Classified as Preductal & Postductal
types, but mostly the constriction lies
distal to the origin of subclavian artery
opposite the ductus arteriosus
(Juxtaductal)
Preductal type:
 Less common.
 The narrowing is proximal to the
ductus arteriosus.
 If severe, blood flow to the aorta
distal to the narrowing (supplying
lower body) depends on a patent
ductus arteriosus, and hence its
closure can be life-threatening.
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Postductal type
 Most common.
 The narrowing is distal to the ductus
arteriosus.
 The ductus usually remains open to
communicate pulmonary artery with the
descending aorta
 Even with an open ductus arteriosus blood
flow to the lower body can be impaired.
 Allows development of collateral
circulation during the fetal period. The
collateral circulation will develop mainly
by branches from both subdavian arteries,
scapular, internal thoracic and intercostal
arteries.
 It is associated with notching of the ribs,
hypertension in the upper extremities, and
weak pulses in the lower extremities.
Right Arch of Aorta
Occurs when the entire right aortic arch
persists &the segment of left dorsal
aorta distal to the 7th intersegmental
artery involutes
TYPES:
 Without retropharyngeal component: The
DA passes from right pulmonary artery to right
arch of aorta. No effect on the trachea &
esophagus
 With retropharyngeal component:
The right arch lies posterior to
esophagus. The attachment of DA to
distal part of the arch of aorta forms a
ring around the trachea & esophagus
and may lead to their compression
Double Arch of Aorta
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Characterized by a vascular
ring encircling the trachea
and esophagus, usually
causing compression of both
structures.
The degree of compression
varies
Usually the right arch is
larger and passes posterior to
the esophagus
The right common carotid
and subclavian arteries arise
separately from right arch
RCC
RSA
LCC
LSA
Patent Ductus Arteriosus
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Before birth, the aorta and
the pulmonary artery are
normally connected by a
blood vessel called the
ductus arteriosus, which is an
essential part of the fetal
circulation.
After birth, the vessel is
supposed to close within a
few days. The obliterated
vessel forms the ligamentum
arteriosum.
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In some babies, the
ductus arteriosus
remains open (patent).
This allows blood to
flow directly from the
aorta into the
pulmonary artery,
which can put a strain
on the heart and
increase pressure in the
pulmonary circulation
Abnormal Right Subclavian Artery
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May arise from the
distal part of arch of
aorta
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In some cases, the right
subclavian artery arises
from the descending
aorta and runs behind
the trachea and the
esophagus to supply
the right upper limb
Thank You
&
Good Luck