Question
A 56-year-old man is brought to the emergency department 25 minutes after the sudden onset of severe pain in the middle of his chest. He describes the pain as tearing in quality; it radiates to his jaw. He has hypertension. He has smoked one pack of cigarettes daily for the past 25 years. Current medications include enalapril. His blood pressure is 154/95 mm Hg in his right arm and 181/105 mm Hg in his left arm. A CT scan of the chest is shown. The structure indicated by the arrow is a derivative of which of the following?
| A. |
Bulbus cordis
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| B. |
Truncus arteriosus
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| C. |
Primitive atrium
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| D. |
Right common cardinal vein
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Show Answer
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Correct Answer � B
Explanation
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Answer B) Truncus arteriosus
The structure indicated by the arrow is the ascending aorta.
Truncus arteriosus
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The truncus arteriosus forms early in cardiac development at the cranial end of the bulbus cordis and gives rise to the pulmonary trunk and ascending aorta.
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During cardiac development, neural crest and endocardial cells migrate to form truncal ridges and bulbar ridges from the truncus arteriosus and bulbus cordis, respectively.
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Truncal and bulbar ridges spiral and fuse to form the aorticopulmonary septum (AP septum), thereby creating the independent ascending aorta and pulmonary trunk.
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Incomplete formation of the aorticopulmonary septum results in persistent truncus arteriosus, which presents at birth with cyanosis, heart failure, and a harsh holosystolic murmur at the left lower sternal border.
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The patient presents with sudden-onset of tearing chest pain and asymmetrical blood pressure readings, which suggests aortic dissection.
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Uncontrolled hypertension and smoking are independent risk factors for aortic dissection.
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