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Flashcards in Vascular embryology Deck (37):

Vascular Development • Occurs by 2 mechanisms

Vasculogenesis • Coalescence of angioblasts • I.e.: Major vessels such as the dorsal aorta and cardinal veins.
• Angiogenesis • Vessels sprout from existing vessels • I.e.: Remainder of vascular system


The early embryonic vascular system is a complex network • preferential flow related to

the development of organs leads to
enlargement of some vessels while other vessels are obliterated.


This enlargement of vessels is by way

of fusion with smaller vessels and partly by enlargement of individual capillary beds.


The major arterial conduits in the early embryo are the

dorsal aortas


dorsal aortas are a continuation of

the endocardial tubes. • Arise from the Aortic Sac (Distal most part of the truncus arteriosus)


Because of the changing position of the developing heart tube and pericardium, the cranial portions of the dorsal aortas

come to describe an arc on both sides of the foregut, establishing the first pair of aortic arches.


max pairs of aortic arches present

6 pairs


which aortic arch is transient

5th aortic arch is only transient.
• 5th Aortic Arch never forms or forms incompletely and regresses


aortic arch numbers

I, II, III, IV, and VI


As the aortic arches develop, some

become modified and other regress


3 mm Embryo

• The first pair of arches is large • Second pair is just forming • All the other arches develop from the region of the aortic sac. • Distally (not shown here), the dorsal aortas fuse to form a single vessel.


4 mm Embryo day 27

Aortic arch I has largely disappeared
• Part of it remains - becomes the Maxillary Artery.
• Aortic arch II is regressing. • Remnants of arch II – becomes the
Stapedial Artery.
Aortic arch III is already large and well developed.
Aortic arches IV and VI are being formed as ventral and dorsal sprouts.
Notice that aortic arch VI already has a sprouting branch of the primitive pulmonary artery.


10mm Embryo – Day 29

The first two aortic arches have disappeared
• Aortic arches III, IV, and VI are quite large.
• The truncoaortic sac has been divided so that arch VI is now continuous with the pulmonary trunk.
• Starting to lose symmetry
• The intersegmental arteries will be important in the formation of the subclavian arteries.


14mm Embryo

The symmetrical pattern is largely gone.
• There is further division of the aorta and pulmonary artery.
• Arch III forms the common carotid artery and first part of the internal carotid artery
• Arch IV stays on each side but becomes different structures.
• Left Arch IV – part of Aortic arch between LCC and L. Subclavian
• Right Arch IV – Proximal R. Subclavian
• The dorsal portion of the right arch VI has disappeared and the left arch VI will become the ductus arteriosus.
Notice the intersegmental arteries have migrated upward to become the subclavian arteries.
Arch VI (aka. Pulmonary Arch)
• Gives off branches that grows toward the developing lung buds
• The dorsal portion of the right arch VI has disappeared and the left arch VI will become the ductus arteriosus.


17mm Embryo

A portion of the vessel that was formerly the right dorsal aorta disappears.
• Proximal portion persists and becomes the right subclavian artery.


At Birth

At birth, the distal part of the left sixth aortic arch (the ductus arteriosus) normally obliterates
• ligamentum arteriosum.
• The adult aortic arch system is now established.


Aortic Sac becomes

• Ascending Aorta • Aortic Arch • Brachiocephalic Artery


first arches become

Maxillary Artery (portion)


second arches become

Stapedial Artery (portion)


third arches become

Carotid Arteries


Fourth Arches become

• Right – Proximal Right Subclavian Artery
• Left – Aortic arch segment between left carotid and left subclavian artery


Fifth Arches become

transient and never develop


Sixth Arches

• Right – • Proximal - Proximal right pulmonary artery • Distal - distal portion disappears
• Left – • Proximal – Proximal left pulmonary artery • Distal–DuctusArteriosus


Right Dorsal Aorta

Portion becomes the right subclavian


Left Dorsal Aorta

• Distal aortic arch and descending aorta


Right Intersegmental Artery

• Part of right subclavian artery


Left Intersegmental Artery

• Left subclavian artery


major point of entry into the common atria.

The sinus venosus


The sinus venosus remains paired

until the embryo is 4 mm


in a 4 mm embryo, there is a distinguishable

Central (unpaired) portion, • Transverse portion • Right and left sinus horns.


Vitelline veins

Carry blood from the yolk sac to the
sinus venosus


Umbilical veins

Originate in the chorionic villi and carry
oxygenated blood to the embryo


Common cardinal veins

Drain the body of the embryo


In the primitive heart (tube), the left and right sinus horns drain

into a central sinoatrial orifice.


Vitelline venous system

Enters the sinus venosus • Gives rise to the hepatic veins


Umbilical venous system

Enter the sinus venosus lateral to the vitelline veins. • Persists as the umbilical vein in the term fetus.


Cardinal venous system

• Enters the sinus venosus lateral/superior to the umbilical veins • Forms a large complex network of veins throughout the body.