2. The Aortic Arches

3. Objectives Describe the formation of the aortic arches. Describe the formation of the aortic arches. Enlist the derivatives of aortic arches. Enlist the derivatives of aortic arches. Discuss the development of venous system of the heart. Discuss the development of venous system of the heart. Differentiate between fetal and neonatal circulation. Differentiate between fetal and neonatal circulation. Discuss the congenital anomalies of the aortic arches. Discuss the congenital anomalies of the aortic arches.

4. Aortic Arches The aortic arches are a series of paired arterial channels encircling the embryonic pharynx The aortic arches are a series of paired arterial channels encircling the embryonic pharynx They: They:  Develop in the 4 th week  Supply the developing pharyngeal arches  Arise from the aortic sac  Run dorsally, embedded in the mesenchyme of the pharyngeal arches and  Terminate in the right and left dorsal aortae

5. Develop in a craniocaudal sequence Develop in a craniocaudal sequence There are potentially six pairs, but the fifth pair is poorly developed and disappears soon after formation There are potentially six pairs, but the fifth pair is poorly developed and disappears soon after formation Not all the 6 pairs present at the same time. By the time the 6 th aortic arches are formed, the 1 st & 2 nd have disappeared Not all the 6 pairs present at the same time. By the time the 6 th aortic arches are formed, the 1 st & 2 nd have disappeared In the region of aortic arches, the dorsal aortae remain paired, but caudal to this region they fuse to form a single median vessel In the region of aortic arches, the dorsal aortae remain paired, but caudal to this region they fuse to form a single median vessel Aortic --sac

6. During week 6 to 8, the primitive aortic arch pattern is transformed into the adult arterial arrangement of carotid, subclavian, and pulmonary arteries During week 6 to 8, the primitive aortic arch pattern is transformed into the adult arterial arrangement of carotid, subclavian, and pulmonary arteries

7. Derivatives of Aortic Arches

8. First Pair Largely disappear Largely disappear Dorsal part persists as the maxillary arteries which supply the ear, teeth and muscles of the eyes and face Dorsal part persists as the maxillary arteries which supply the ear, teeth and muscles of the eyes and face May give rise to the external carotid artery May give rise to the external carotid artery The first arch is obliterated before the 6 th arch is formed

9. Second Pair Largely disappear Largely disappear Dorsal part persists as the hyoid and stapedial arteries Dorsal part persists as the hyoid and stapedial arteries

10. Third Pair Proximal part: forms the common carotid arteries Proximal part: forms the common carotid arteries Distal part: joins the dorsal aortae to form the internal carotid arteries Distal part: joins the dorsal aortae to form the internal carotid arteries

11. Fifth Pair Disappears completely with NO vascular derivatives Disappears completely with NO vascular derivatives

12. The fate of 4 & 6 th pairs of aortic arches differs on the right and left side

13. Fourth Pair RIGHT: Becomes the proximal part of the right subclavian artery RIGHT: Becomes the proximal part of the right subclavian artery LEFT Forms part of the arch of aorta LEFT: Forms part of the arch of aorta

14. Arch of Aorta Derived as: Proximal segment from aortic sac Proximal segment from aortic sac Middle segment from the left 4 th aortic arch Middle segment from the left 4 th aortic arch Distal segment from the left dorsal aorta Distal segment from the left dorsal aorta

15. Subclavian Artery The right subclavian artery formed from the: The right subclavian artery formed from the:  Right 4 th aortic arch  Right dorsal aorta &  Right 7 th intersegmental artery The left subclavian artery formed from the left 7 th intersegmental artery The left subclavian artery formed from the left 7 th intersegmental artery

16. Sixth Pair RIGHT: RIGHT: Proximal part: persists as the proximal part of the right pulmonary arteryProximal part: persists as the proximal part of the right pulmonary artery Distal part: degeneratesDistal part: degenerates LEFT: LEFT: Proximal part: persists as the proximal part of the left pulmonary arteryProximal part: persists as the proximal part of the left pulmonary artery Distal part: forms ductus arteriosus, a shunt between pulmonary artery and dorsal aortaDistal part: forms ductus arteriosus, a shunt between pulmonary artery and dorsal aorta

17. Changes in the original aortic arch system Obliteration of: Obliteration of: 1.Most of the 1 st & 2nd arches 2.5 th arches completely 3.Distal part of the right sixth arch 4.The segment of both aortae lying between the 3 rd & 4 th arches 5.The segment of right aorta lying between the 7 th intersegmental artery & the fused dorsal aortae

18. Relation of recurrent laryngeal nerves to the aortic arches

19. Anomalies of the Aortic Arches

20. Coarctation of Ao rta Characterized by narrowing of aorta Characterized by narrowing of aorta More common in males More common in males Classified as Preductal & Postductal types, but mostly the constriction lies distal to the origin of subclavian artery opposite the ductus arteriosus (Juxtaductal) Classified as Preductal & Postductal types, but mostly the constriction lies distal to the origin of subclavian artery opposite the ductus arteriosus (Juxtaductal) Preductal type: Preductal type:  Less common.  The narrowing is proximal to the ductus arteriosus.  If severe, blood flow to the aorta distal to the narrowing (supplying lower body) depends on a patent ductus arteriosus, and hence its closure can be life-threatening.

21. Postductal type Postductal type  Most common.  The narrowing is distal to the ductus arteriosus.  The ductus usually remains open to communicate pulmonary artery with the descending aorta  Even with an open ductus arteriosus blood flow to the lower body can be impaired.  Allows development of collateral circulation during the fetal period. The collateral circulation will develop mainly by branches from both subdavian arteries, scapular, internal thoracic and intercostal arteries.  It is associated with notching of the ribs, hypertension in the upper extremities, and weak pulses in the lower extremities.

22. Right Arch of Aorta Occurs when the entire right aortic arch persists &the segment of left dorsal aorta distal to the 7th intersegmental artery involutes Occurs when the entire right aortic arch persists &the segment of left dorsal aorta distal to the 7th intersegmental artery involutes TYPES:  Without retropharyngeal component: The DA passes from right pulmonary artery to right arch of aorta. No effect on the trachea & esophagus  With retropharyngeal component: The right arch lies posterior to esophagus. The attachment of DA to distal part of the arch of aorta forms a ring around the trachea & esophagus and may lead to their compression

23. Double Arch of Aorta Characterized by a vascular ring encircling the trachea and esophagus, usually causing compression of both structures. The degree of compression varies Usually the right arch is larger and passes posterior to the esophagus The right common carotid and subclavian arteries arise separately from right arch RSALSA LCCRCC

24. Patent Ductus Arteriosus Before birth, the aorta and the pulmonary artery are normally connected by a blood vessel called the ductus arteriosus, which is an essential part of the fetal circulation. Before birth, the aorta and the pulmonary artery are normally connected by a blood vessel called the ductus arteriosus, which is an essential part of the fetal circulation. After birth, the vessel is supposed to close within a few days. The obliterated vessel forms the ligamentum arteriosum. After birth, the vessel is supposed to close within a few days. The obliterated vessel forms the ligamentum arteriosum.

25. In some babies, the ductus arteriosus remains open (patent). In some babies, the ductus arteriosus remains open (patent). This allows blood to flow directly from the aorta into the pulmonary artery, which can put a strain on the heart and increase pressure in the pulmonary circulation This allows blood to flow directly from the aorta into the pulmonary artery, which can put a strain on the heart and increase pressure in the pulmonary circulation

26. Abnormal Right Subclavian Artery May arise from the distal part of arch of aorta May arise from the distal part of arch of aorta In some cases, the right subclavian artery arises from the descending aorta and runs behind the trachea and the esophagus to supply the right upper limb In some cases, the right subclavian artery arises from the descending aorta and runs behind the trachea and the esophagus to supply the right upper limb

27. Thank You & Good Luck Thank You & Good Luck