Aortic Arches

Question 1

What is the pharyngeal arch?

Answer 1

The pharyngeal arch is one of the components of the pharyngeal apparatus
-Apparatus is responsible for the formation of the face and neck

Question 2

When does the pharyngeal arch develop?

Answer 2

Begins to develop early in the 4th week

-Neural crest cells migrate into the future head and neck regions and contribute to the formation

Question 3

How are pharyngeal arches numbered?

Answer 3

Arches are numbered in a craaniocaudal sequence

-A total of 6 pairs of arches

Question 4

Where are pharyngeal arches derived from?

Answer 4

The pharyngeal arches contains representation from all germ layers

Question 5

What are the components of the pharyngeal arch?

Answer 5

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

Question 6

Summarize the significance and origins of aortic arches

Answer 6

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

Question 7

What is the impact of the aortic sac?

Answer 7

• 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

Question 8

Outline the circulation through the fetal/ primordial heart

Answer 8

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

Question 9

When is the first aortic arch obliterated?

Answer 9

The first arch is oblitered before the sixth is formed

Question 10

What does the first aortic arch do?

Answer 10

1 st arch largely disappears (day 27)

-small part remains and forms the maxillary artery

Question 11

What does the 2nd aortic arch do?

Answer 11

2nd arch later disappears

Remaining parts are the hyoid and stapedial arteries

Question 12

What does the 3rd aortic arch form?

Answer 12

• common carotid artery

- first part of the internal carotid

Question 13

What does the 4th aortic arch do?

Answer 13

• on the left forms part of the arch of the aorta

- on the right forms the most proximal part of the Subclavian artery

Question 14

What does the 5th arch do?

Answer 14

Either forms incompletely and regresses, or never forms

Question 15

What does 6th aortic arch do?

Answer 15

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

Question 16

What is the first arch/first arch artery adult derivative?

Answer 16

Degenerates

Remnants form part of the maxillary arteries (supplies the ears, teeth, facial and eye muscles

Parts of the external carotid arteries

Question 17

What is the adult derivative of the second arch/second arch artery?

Answer 17

Degenerates

Remnants forms stapedial and hyoid arteries

Question 18

What is the adult derivative of the third arch/third arch artery?

Answer 18

Proximal parts form the common carotid

Distal parts join with the dorsal aortae to form the internal carotids

Question 19

What is the fourth arch/fourth arch artery adult derivative?

Answer 19

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

Question 20

What is the adult derivative of the fifth arch/ fifth arch artery ?

Answer 20

Usually degenerates with no vascular derivatives

Question 21

What is the adult derivative of the sixth aortic arch/ sixth aortic arch artery?

Answer 21

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

Question 22

What is the fate of the dorsal aortae?

Answer 22

• Right disappears between the origin 9f the 7th intersegmental artery and the junction with the left dorsal aorta
• Caudal part forms the descending aorta

Question 23

What are the recurrent laryngeal nerves?

Answer 23

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

Question 24

Describe the recurrent course of the. Recurrent laryngeal nerves

Answer 24

• 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

Question 25

Describe normal development of the right Subclavian artery

Answer 25

Right 4th artery
-forms proximal part of Subclavian artery

Right dorsal artery and right 7th intersegmental artery
-forms distal part of Subclavian artery

Question 26

Describe the pathology of the anamolies right Subclavian artery

Answer 26

• 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

Question 27

Describe development of the double aortic arch

Answer 27

Normal development:

• proximal arch
  
  • left 4th aortic arch and aortic sac
• distal arch
• left dorsal aorta

Question 28

Describe pathogenesis of double aortic arch

Answer 28

• 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

Question 29

Describe the normal development of right aortic arch

Answer 29

• proximal arch
  
  • left 4th aortic arch and aortic sac
• distal arch
  
  • left dorsal aorta

Question 30

Describe pathogenesis

Answer 30

• 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

Question 31

What are the two types of right aortic arch?

Answer 31

• 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
  -Ligamentum arteriosum attaches to the distal part of the arch and forms a ring which can compress trachea and esophagus