[Verse 1]
One great vessel leaves the heart, straddling the wall that split in two,
Systemic, lung, and coronary — all drink from the trunk it grew through.
Call it common, call it singular, the septum never closed its door,
This is the ground floor of the lesson, before we count the forms it wore.
[Chorus]
Two mouths, one wall — that's the Collett-Edwards call,
Posterior, posterolateral, side by side they fall.
No trunk between them, just a fork where the vessel splits in air,
Type Two, Type Two — separate holes but the same lung pair.
[Verse 2]
Picture the back of that single artery, low and leaning behind,
Right and left pulmonary arteries rising, adjacent, intertwined.
Not fused into one stem like Type One's single pulmonary door,
Two distinct ostia, close as neighbors, but each one keeps its own floor.
[Chorus]
Two mouths, one wall — that's the Collett-Edwards call,
Posterior, posterolateral, side by side they fall.
No trunk between them, just a fork where the vessel splits in air,
Type Two, Type Two — separate holes but the same lung pair.
[Verse 3]
Cross the aisle to Van Praagh's naming, A2 answers the same design,
No main pulmonary segment standing, just two origins in a line.
Different language, same anatomy, two systems shaking hands,
Nosology's a translator, not a border drawn in sand.
[Bridge]
Now a few millimeters of pulmonary trunk can blur the line we drew,
Type One bleeds softly into Two — the textbook isn't always true.
Surgeons say the difference matters little once the patch is sewn,
Classification's a compass, not the shape of flesh and bone.
[Verse 4]
One, maybe two, in a hundred hearts wear this truncal design,
Type One and Type Two together claim eighty-five of every line.
Rare enough to study closely, common enough to bear a name,
Know the boxes, know their limits — the anatomy's still the same.
[Verse 5]
Back in the fourth week, the truncal ridges spiral and try to meet,
A conotruncal fault line lingers where the septum fails to complete.
Neural crest cells whisper the pattern, migration falling short,
Leaving one artery to answer for what should have been two doors at the aorta's court.
Echo the arch, echo the valve, watch how the leaflets divide,
Every subtype tells the same story of a septum that never tied.
[Chorus]
Two mouths, one wall — that's the Collett-Edwards call,
Posterior, posterolateral, side by side they fall.
No trunk between them, just a fork where the vessel splits in air,
Type Two, Type Two — separate holes but the same lung pair.
[Outro]
Separate ostia, posterior wall, no trunk to bridge the two —
Hold the picture, not the label, and the anatomy sees you through.