Question:
During embryonic development of the heart, looping occurs to align cardiac chambers. Which of the following is true?
During embryonic development of the heart, looping occurs to align cardiac chambers. Which of the following is true?
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Key Cardiac Embryology: Looping starts at Day 22 (4th week) $\rightarrow$ D-looping (bends to the right) regulated by left-sided master gene PITX2c (via Nodal/Lefty cascade).
Updated On: Sep 3, 2026
- Looping occurs on left side
- During looping LV aligns with truncus arteriosus
- Asymmetric signalling regulated the direction of looping
- Cardiac looping starts at 5th week of gestation
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The Correct Option is C
Solution and Explanation
Concept:
Cardiac looping (d-looping) is a fundamental morphogenetic process during early embryonic heart development that breaks bilateral symmetry to establish the normal left-right spatial orientation (situs solitus) of the cardiac chambers and great vessels.
Explanation:
• The primitive straight cardiac tube begins to loop during the 4th week of human development (approximately day 22--23, completing by day 28), not the 5th week.
• In normal development (dextro-looping), the straight heart tube bends to the right side (d-loop) and anteriorly, bringing the primitive ventricle to the left and shifting the primitive atrium dorsally and cranially.
• The direction of cardiac looping is tightly orchestrated by an evolutionary conserved cascade of asymmetric left-right signaling pathways, mediated by nodal cilia, left-sided expression of NODAL, LEFTY-2, and the homeobox transcription factor PITX2c.
• Disruption of this asymmetric molecular signaling leads to abnormal looping (l-looping), resulting in L-transposition (congenitally corrected TGA), heterotaxy syndromes, or dextrocardia.
• During looping, the primitive right ventricle (bulbus cordis) aligns with the truncus arteriosus, while the primitive ventricle forms the left ventricle and aligns with the atrioventricular canal.
Final Answer:
The accurate statement regarding cardiac looping is that asymmetric molecular signaling regulates the direction of looping.
Cardiac looping (d-looping) is a fundamental morphogenetic process during early embryonic heart development that breaks bilateral symmetry to establish the normal left-right spatial orientation (situs solitus) of the cardiac chambers and great vessels.
Explanation:
• The primitive straight cardiac tube begins to loop during the 4th week of human development (approximately day 22--23, completing by day 28), not the 5th week.
• In normal development (dextro-looping), the straight heart tube bends to the right side (d-loop) and anteriorly, bringing the primitive ventricle to the left and shifting the primitive atrium dorsally and cranially.
• The direction of cardiac looping is tightly orchestrated by an evolutionary conserved cascade of asymmetric left-right signaling pathways, mediated by nodal cilia, left-sided expression of NODAL, LEFTY-2, and the homeobox transcription factor PITX2c.
• Disruption of this asymmetric molecular signaling leads to abnormal looping (l-looping), resulting in L-transposition (congenitally corrected TGA), heterotaxy syndromes, or dextrocardia.
• During looping, the primitive right ventricle (bulbus cordis) aligns with the truncus arteriosus, while the primitive ventricle forms the left ventricle and aligns with the atrioventricular canal.
Final Answer:
The accurate statement regarding cardiac looping is that asymmetric molecular signaling regulates the direction of looping.
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