Vascular embryology Flashcards
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.
