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.
