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Embryo a arch
Arches, pouches, clefts
Question | Answer |
---|---|
Anterior extensions of dorsal aortae into head | Distal 2/3 of ICA |
Aortic sac of truncus arteriosus | External carotid arteries |
1st aortic arch | Regresses at 4 weeks (small portion forms part of maxillary artery) |
2nd aortic arch | Regresses (except for very small amount which forms stapedius and hyoid arteries) |
3rd aortic arch | Common carotid arteries and proximal 1/3 of ICA |
Left 4th aortic arch | Part of arch of aorta, btwn left common carotid and left subclavian aa |
Right 4th aortic arch | Proximal part of right subclavian |
5th aortic arch | Transient |
Proximal left 6th aortic arch | Proximal part left pulmonary artery |
Distal left 6th aortic arch | Ductus arteriosus |
Proximal right 6th aortic arch | Proximal right pulmonary artery |
Distal right 6th aortic arch | Regresses |
Left subclavian artery forms from | Left 7th intersegmental artery |
Right subclavian artery forms from | Proximal: right 4th aortic arch Distal: right 7th intersegmental |
Aortic sac of truncus arteriosus forms | Brachiocephalic artery, proximal arch of aorta |
What forms arch of aorta | Aortic sac of truncus arteriosus, left 4th aortic arch, left dorsal aorta |
1st pharyngeal pouch | Tubotympanic recess--forms middle ear and auditory tube |
2nd pharyngeal pouch | Tonsilar fossa and palatine tonsils |
Dorsal 3rd pouch | Inferior parathyroid |
Ventral 3rd pouch | Thymus |
Dorsal 4th pouch | Superior parathyroid |
Ventral 4th pouch | Ultimobranchial body |
1st pharyngeal cleft | External auditory meatus, outer ectodermal eardrum |
2nd, 3rd, 4th clefts | No derivatives |
What happens to clefts 2,3,4 | 2nd arch grows caudally, overlaps 3,4; fuses with epicardial ridge, forming cervical sinus. |