NBME 21 External carotid (NBME Answers)

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Retired NBME 21 Answers

nbme21/Block 3/Question#27 (reveal difficulty score)
A 55-year-old woman with a benign nodule in ...
External carotid 🔍 / 📺 / 🌳 / 📖
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submitted by ∗hayayah(1212)

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The thyroid is supplied with arterial blood from the superior thyroid artery, a branch of the external carotid artery, and the inferior thyroid artery, a branch of the thyrocervical trunk.

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sahusema https://imgur.com/0uBvexe +6

ahwl1111 for visual: https://www.youtube.com/watch?v=io1kDkj1Enk +

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submitted by ∗sharpscontainer(17)

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I was duped; did anybody here get it wrong because they thought about the thyroid ima artery arising from the brachiocephalic trunk? No? Just me? Okay.

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peridot Ooh that is tricky tricky. In the question stem they said they already ligated that one ("a branch of the brachiocephalic trunk") and were wondering what else needs to be ligated in addition to that. Therefore the answer is the superior thyroid artery, which is coming from the external carotid. I don't think I knew any of this when I did the question though, cause I had to google all this just now. +1

anechakfspb In the stem they said they ligated a branch of the thyrocervical trunk, not the brachiocephalic. According to Wiki, the thyroid ima artery (which does arise from the brachiocephalic trunk) is only present in about 3-10% of the population. Therefore, while technically this answer could be correct, external carotid is "more correct". Source: https://en.wikipedia.org/wiki/Thyroid_ima_artery +1

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submitted by ∗schep(44)

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A refresher on the branches of external carotid artery-SALFOPMaxS

Superior thyroid, Ascending pharyngeal, Lingual, Facial, Occipital, Posterior auricular, Maxillary and Superficial temporal

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