NBME Free 120 Branch of the thyrocervical trunk (NBME Answers)

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free120/Block 2/Question#24 (reveal difficulty score)
A 33-year-old man undergoes a radical ...
Branch of the thyrocervical trunk 🔍 / 📺 / 🌳 / 📖
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submitted by ivypoison(6)

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Why high PTH 200pg/ml (normal <60)? it should be primary hypoparathyroidism!

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amm13e i think with no proper Blood supply, the PTH cant sample the Ca2+ levels in the blood, making the gland secrete more PTH +7

castlblack secrete pth into where? the lost blood supply it doesn't have? Also, there are no parathyroid glands because the dude had a thyroidectomy! +2

alimd @castlblack maybe they left it hanging of the fucking veins))) +2

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submitted by ∗bwdc(697)

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This question is asking for the vascular supply of the parathyroid glands. That would be the inferior thyroid arteries, which arise from the thyrocervical trunk.

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focus Diagram: https://www.sciencedirect.com/topics/medicine-and-dentistry/inferior-thyroid-artery +1

weenathon I originally chose vein because I was thinking maybe the hormone release couldn't be carried to the body anymore, but looking back the working of "moderate hemorrhaging" and vessels requiring ligation is what implies it's an artery. Just throwing that out there in case you thought like I did. +6

cheesetouch if you were clueless like me (well I knew artery but..), picking one with 'thyro' in the name when discussing a thyroid surgery is a good guess :) +10

cbreland I'm really out here picking one of the answers with vein +2

cheesetouch Anatomy image: https://image.slidesharecdn.com/thyroidgland-150501155351-conversion-gate01/95/thyroid-gland-14-638.jpg?cb=1430513690 FA18 p 338 relates to thyroidectomy +1

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submitted by ∗t123(32)

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PMID 8165531

Both superior thyroid (ext carotid) and inferior thyroid (thyrocervical) supply the parathryoids. Bad q...

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tekkenman101 Main supply to parathyroids is inferior, so no. +1

mistermbg "The thyroid gland and the parathyroid glands share the same blood supply. The inferior thyroid arteries supply the parathyroid glands via its branches (supplying both the inferior and superior parathyroids in most cases). Collaterals via the superior thyroid artery, thyroid ima artery, laryngeal, tracheal, and esophageal arteries. Parathyroid veins drain into the thyroid vein plexus." https://www.ncbi.nlm.nih.gov/books/NBK537203/#:~:text=Blood%20Supply%20and%20Lymphatics,-The%20thyroid%20gland&text=The%20inferior%20thyroid%20arteries%20supply,%2C%20tracheal%2C%20and%20esophageal%20arteries. the MAIN SUPPLY IS FROM THE INFERIOR THYROID ARTERIES. the little bit of blood received from the collateral keeps them alive but now they sense low ca2+ --->>> so release tons of PTH... if the superior was knocked out = not a big deal --> not main supply to the glands. +2

burak everyone keeps saying it is sensing low ca level so secreting more pth. But Ca is already low so it is not sensing anything wrongly. Or I am just blind i dont know. +1

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submitted by ∗niboonsh(409)

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external carotid branch supplies the superior parathyroid glands as well........?

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yng Yes the superior part supplied by superior thyroid gland which is a branch of external carotid branch. +1

llamastep1 No they do not, parathyroids are supplied by the inferior thyroid arteries. https://teachmeanatomy.info/neck/viscera/parathyroid-glands/ +15

suckitnbme Superior thyroid artery does supply some blood to the parathyroids through anastomoses but the main vascular supply is from the inferior thyroid artery. +2

okokok1 https://www.earthslab.com/wp-content/uploads/2017/07/070417_1014_Parathyroid1-1.jpg this shows a great visual of how inferior thyroid artery does most of the supplying. +1

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submitted by ∗jbrito718(48)

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the MAIN SUPPLY IS FROM THE INFERIOR THYROID ARTERIES. the little bit of blood received from the collateral (superior thyroid from external carotid) keeps them alive but now they sense low ca2+ --->>> so release tons of PTH... if the superior was knocked out = not a big deal --> not main supply to the glands.

** I copied @mistermbg explanation because he explains it really well!

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