الصورة الشعاعية في تضيق برزخ الأبهر:

Explain anatomically why the notch is on the lower margin of the rib ?

becuase the intercostal neurovascular bundle runs in the inferior border on the rib in the order VAN
Vein , Artery , Nerve

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REMBMEMR

the infantile coarctation of aorta-preductal- is due to tubular hypoplasia

the adult coarctation of aorta-postductal- is due to ridge like folding

but that doesnt mean that the adult type doesnt occur in children
it occurs in children and continues through life
( obstructive conginetal heart disease )
but since the charctaristic collateral circulation development occurs in adult life time thats why its called adult type