Which of the following represent the commonest variation in the aeries arising from the arch of aoa?
**Core Concept**
In human anatomy, the aortic arch (arch of aorta) is a curved portion of the aorta that arises from the left ventricle of the heart. It gives off several branches that supply blood to the head, neck, and upper limbs. Variations in the branching pattern of these arteries are common and can be clinically significant.
**Why the Correct Answer is Right**
The commonest variation in the arteries arising from the aortic arch is the presence of a right-sided brachiocephalic artery (also known as a right brachiocephalic trunk). Normally, the brachiocephalic artery arises from the aortic arch as a left-sided branch, which then divides into the right common carotid and right subclavian arteries. However, in approximately 85% of individuals with this variation, the right brachiocephalic artery arises directly from the aortic arch, bypassing the normal left-sided origin.
**Why Each Wrong Option is Incorrect**
**Option A:** The bovine arch, which involves a right-sided brachiocephalic artery, is indeed a common variation but is not the most common one. It is characterized by a right-sided brachiocephalic artery that arises from the aortic arch, but it also involves a separate left-sided brachiocephalic artery that arises from the left side of the aortic arch.
**Option B:** The circumflex aortic arch is a rare variation where the left subclavian artery arises from the right side of the aortic arch.
**Option C:** The double aortic arch is a rare congenital anomaly where two aortic arches encircle the trachea and esophagus, but it is not a variation in the branching pattern of the arteries from the aortic arch.
**Option D:** There is no such variation as a "tripartite aortic arch" in human anatomy.
**Clinical Pearl / High-Yield Fact**
When performing angiography or other imaging studies of the aortic arch, it is essential to be aware of common variations in the branching pattern to avoid misinterpretation of the anatomy.
**Correct Answer: C. The circumflex aortic arch is a rare variation where the left subclavian artery arises from the right side of the aortic arch.**