Heart tube looping, cardiac septation steps, and the specific congenital heart defect tied to each disrupted step tested on USMLE Step 1.
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- From what type of mesoderm does the primitive heart tube develop?
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Splanchnic (lateral plate) mesoderm- Around what day of gestation does the primitive heart begin to beat?
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Day 22- In normal development, which direction does the primitive heart tube loop?
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To the right (rightward, D-looping)- What congenital defect results when the heart tube loops to the left instead of the right?
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Dextrocardia- Listed from the venous to the arterial end, the primitive heart tube's five segments are the sinus venosus, primitive atrium, primitive ventricle, bulbus cordis, and ____.
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truncus arteriosus- What right atrial structure develops from the sinus venosus?
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The smooth-walled part (sinus venarum)- What right atrial structure develops from the primitive (embryonic) atrium?
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The rough, trabeculated right auricle- What is the first septum to form within the primitive atrium?
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The septum primum- What is the transient opening between the septum primum and the endocardial cushions, before it fuses, called?
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The ostium primum (foramen primum)- As the ostium primum closes, what new opening forms from perforations in the septum primum?
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The ostium secundum- What second atrial septum forms to the right of the septum primum?
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The septum secundum- What is the opening in the septum secundum called?
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The foramen ovale- An ostium primum atrial septal defect results from failure of which structures to fuse?
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The septum primum and the endocardial cushions- An ostium primum ASD is classically associated with which condition?
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Down syndrome, as part of an AV septal defect- The most common type of atrial septal defect results from excessive resorption of which structure?
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The septum primum, causing an ostium secundum ASD
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