[Verse 1] Right atrium loads, tricuspid's the gate, Three flaps of tissue holding steady weight, Ventricle relaxes, diastole's the cue, Flaps swing open wide, blood comes pouring through, Squeeze comes next, systole tightens the room, Three leaflets slam shut, no backflow, no boom, Chordae tendineae anchor every hinge, One-way door, no reverse, no fringe. [Chorus] Tri, pulmo, mitral, aortic — count the four, Blood walks forward, never through the back door, Three and three then two and three, that's the leaflet code, Doors that open once and shut — that's the one-way road. [Verse 2] Right ventricle's loaded, now it's pushing time, Pulmonary valve's semilunar, moon-shaped design, Three cusps like parachutes catching the tide, Systole fires, they flatten and slide, Lungs get the blood, oxygen's the goal, Diastole comes, cusps snap and control, No backflow to the chamber, the pressure holds true, Semilunar sentry standing guard for you. [Chorus] Tri, pulmo, mitral, aortic — count the four, Blood walks forward, never through the back door, Three and three then two and three, that's the leaflet code, Doors that open once and shut — that's the one-way road. [Verse 3] Cross to the left side, mitral's the name, Two leaflets only, a bishop's hat's the claim, Atrium fills, the ventricle takes a rest, Diastole opens the double-flap chest, Then the squeeze — aortic valve takes the call, Three semilunar cusps guard the great wall, Systole blasts blood out to the aorta's bend, Backflow to the ventricle? Not on my watch, friend. [Verse 4] Stenosis stiffens, the doorway grows tight, Blood fights the leaflets, squeezing through fright, Regurgitation's the leak when the seal fails, Backflow sneaks past, the pressure derails, Murmurs sing out when the flow turns rough, Doctors listen close, the heartbeat's the proof, Four valves, one rhythm, keep the blood in line, Guard the gates well, and the heart runs fine. [Bridge] Now picture the split that never occurred, Pulmonary and aortic, one root, one word, Truncus arteriosus — the valves never divide, A single truncal valve, nothing to separate the tide, Semilunar cousins fused into one seam, An embryo's mistake writes a different scheme, Two vessels reduced to a single doorway wide, One valve, one truncus, no room to divide. [Chorus] Tri, pulmo, mitral, aortic — count the four, Blood walks forward, never through the back door, Three and three then two and three, that's the leaflet code, Doors that open once and shut — that's the one-way road. [Outro] Tricuspid, pulmonary, mitral, aortic — recite the score, Three-three-two-three, the leaflets keep the score, Every valve a one-way door, forward is the law, Backflow's forbidden — that's the final draw.
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