Aortic Arches Flashcards
What is the pharyngeal arch?
The pharyngeal arch is one of the components of the pharyngeal apparatus
-Apparatus is responsible for the formation of the face and neck
When does the pharyngeal arch develop?
Begins to develop early in the 4th week
-Neural crest cells migrate into the future head and neck regions and contribute to the formation
How are pharyngeal arches numbered?
Arches are numbered in a craaniocaudal sequence
-A total of 6 pairs of arches
Where are pharyngeal arches derived from?
The pharyngeal arches contains representation from all germ layers
What are the components of the pharyngeal arch?
Arch artery- Aortic arches
- Arises from the aortic sac
- the most distal part of the truncus arteriosus
- Supplies the pharyngeal arches
- Enters/connects to the dorsal aorta
- Paired structures that runs through the length of the embryo
- The arches and their vessels appear in a cranial to caudal direction
Each arch has its own nerve, cartilage and artery
Cartilage- forms the skeleton of the arch
Muscle- forms the primordium of the muscles in the head and neck
Nerve- supplies the mucosa and muscles derived from each arch
Summarize the significance and origins of aortic arches
The arch arteries arises from the aortic sac of the truncus arteriosus of the tubular heart
Supply each pharyngeal arch
Connects to the paired dorsal aorta
Paired dorsal aorta also receives blood from the umbilical and vitelline arteries
What is the impact of the aortic sac?
- The aortic sac contributed a branch to each new arch as it forms
- As development progresses, this arterial pattern becomes modified, with some vessels regressing completely
- The six aortic arches are numbered I through VI Arch V is often incompletely formed, and then regresses or is never formed
- Note that the dorsal aorta is paired
Outline the circulation through the fetal/ primordial heart
Sinus venosus —> primordial atrium —> (via SA valves and AV valves)—> primordial ventricle via the SA valves and AV canal —> bulbus cordis and truncus arteriosus—> aortic sac—> pharyngeal arch arteries—> dorsal aortae for distribution to the embryo, umbilical vesicle and placenta
When is the first aortic arch obliterated?
The first arch is oblitered before the sixth is formed
What does the first aortic arch do?
1 st arch largely disappears (day 27)
-small part remains and forms the maxillary artery
What does the 2nd aortic arch do?
2nd arch later disappears
Remaining parts are the hyoid and stapedial arteries
What does the 3rd aortic arch form?
- common carotid artery
- first part of the internal carotid
What does the 4th aortic arch do?
- on the left forms part of the arch of the aorta
- on the right forms the most proximal part of the Subclavian artery
What does the 5th arch do?
Either forms incompletely and regresses, or never forms
What does 6th aortic arch do?
This is the pulmonary arch
-On the right, proximal part becomes proximal segment of right pulmonary artery, the distal part degenerates
On the left, the proximal part exomes proximal segment kf left pulmonary artery, distal part persists as the ductus arteriosus
What is the first arch/first arch artery adult derivative?
Degenerates
Remnants form part of the maxillary arteries (supplies the ears, teeth, facial and eye muscles
Parts of the external carotid arteries
What is the adult derivative of the second arch/second arch artery?
Degenerates
Remnants forms stapedial and hyoid arteries
What is the adult derivative of the third arch/third arch artery?
Proximal parts form the common carotid
Distal parts join with the dorsal aortae to form the internal carotids
What is the fourth arch/fourth arch artery adult derivative?
Left artery forms part of the aortic arch
Proximal part develops from the aortic sac
Distal part from the left dorsal aorta
Right artery becomes the proximal part of the right Subclavian
Distal Subclavian forms from the right dorsal artery and right 7th intersegmental
What is the adult derivative of the fifth arch/ fifth arch artery ?
Usually degenerates with no vascular derivatives
What is the adult derivative of the sixth aortic arch/ sixth aortic arch artery?
Left: proximal part persists as the left pulmonary artery
Distal part forms the prenatal shunt (ductus arteriosus)
Right: proximal persists as the proximal part of the right pulmonary artery
Distal part degenerates
What is the fate of the dorsal aortae?
- Right disappears between the origin 9f the 7th intersegmental artery and the junction with the left dorsal aorta
- Caudal part forms the descending aorta
What are the recurrent laryngeal nerves?
These nerves are branches of vagus Nerve originally supplied the 6th pharyngeal arches
As the heart descends, the nerves hook around the 6th aortic arches & second to the larynx
Describe the recurrent course of the. Recurrent laryngeal nerves
- On the right-when the distal part of the 6th aortic arch and the 5th aortic arch disappears, the recurrent laryngeal nerve moves up and hooks around the right Subclavian artery (formed from the right 4th arch)
- On the left- does not move up because the distal part of the 6th aortic arch persists as the ductus arteriosus, which later forms the Ligamentum arteriosum
Describe normal development of the right Subclavian artery
Right 4th artery
-forms proximal part of Subclavian artery
Right dorsal artery and right 7th intersegmental artery
-forms distal part of Subclavian artery
Describe the pathology of the anamolies right Subclavian artery
- obliteration of the right 4th aortic arch and the proximal part of right dorsal aorta
- with persistence of distal part of right dorsal aorta
The anamolous artery crosses the midline behind the esophagus and could compress it, although this is not often tight enough to cause clinical symptoms
Describe development of the double aortic arch
Normal development:
- proximal arch
- left 4th aortic arch and aortic sac
- distal arch
- left dorsal aorta
Describe pathogenesis of double aortic arch
- persistence of right dorsal aorta between the origin of 7th intersegmental artery and it’s junction with left dorsal aorta (fails to disappear)
- a vascular ring surrounds the trachea and esophagus, compressing them and causing problems with breathing and swallowing
Describe the normal development of right aortic arch
- proximal arch
- left 4th aortic arch and aortic sac
- distal arch
- left dorsal aorta
Describe pathogenesis
- persistence of the entire right dorsal aorta and abnormal involution of the distal part of the left dorsal aorta
- THE left Subclavian is formed by the left 4 arch, left dorsal aorta and left intersegmental artery
What are the two types of right aortic arch?
- Without a retro esophageal component
- Ligamentum arteriosum passes from right pulmonary artery to right arch of aorta
- With a retroesophageal component
- Original small arch of aorta involuted leaving right arch of aorta posterior to the esophagus
