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NBME 22 Answers

nbme22/Block 4/Question#47 (45.1 difficulty score)
A 56-year-old woman comes to the physician ...
Maintenance of basement membrane integrity🔍
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 +12  upvote downvote
submitted by bubbles(63),
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aBsetenm mrbmneae einrtgity is hte reetmtinnad of lluf ungl yoevrrce wloogfiln umnyalpor sl.uitn

mauySr:m

)(1 ossl fo snmbetea enmabrem tnryiietg si ilaicrct in niteienrgdm eth n“ptoi fo on ,retrun” nda sterocbutni ot the iiynibatl ot israbeletsh lnorma glnu trutecheciar with tonoiorpm fo rbfisso;i

()2 slos of hailieeplt sl,elc thnediealol es,cll dna nabestme enbmrmea niytrgite ni lausu rsiinettliat apomenuni soaeastcid wthi tiadhocipi lmonupray ifrsoisb asdel ot dsdeyreot ulgn atchuectrrei nda erppaulte obsfsiir;

3)( amnortrsginf worthg -rcβtoaf si cry,aessen but otn nirletey ceufnii,fts to rpemoot tmnprnaee ssrfib;io

)4( spsrnteeti gruniyrirnjia/tnttan/ei si rilccita rof eht napgoropita of isrisfbo;

(5) ctidapihoi rymolpuna ibsisfro si an epaxmel fo a psorsce leeradt to eht isenretspec fo na ins(”tn,a“g)e crhiocn ftma,aliimonn dna of;irsbsi adn

)6( uqnuei slcle rea icltrica laruelcl alypesr ni the rleaguoitn fo brfossii.

:ac onititMn/taii/1c2mc.psohitr/gP2h5e.llwt/vp6wbcm/4.nw4:/snC.

kernicterusthefrog  Lovely +  
endochondral1  any FA or pathoma or uworld correlation? +  
endochondral1  or was this a random? +  
taediggity  Type II pneumocytes serve as the stem cell precursors, w/out those you're more or less fucked: FA 2020 pg 661 +4  



 +9  upvote downvote
submitted by drdoom(646),
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uoY avhe ot tnhki uobat ti siht a:wy eth abesnemt bemnemra si hte ocglff”snad“i no hichw sverratteoi[] hienagl .osrucc ,oS s,ye mtse leslc etp(y II )tuscoempeyn dwoul be lonvidve in ahtt lhaigen peroscs but ehty u’ndtcol ertores the nlroam ttrurcceaieh (“on asb)eamiotnil”r wuotith het eoeln‘sk’t fo hte sbeanetm emmabern lgnitel ethm eewhr to ,go in athw icditnore to ,worg hiwhc yaw si ”p,“u tce. fI het tnasmeeb mnbmaree si redso,tdey oyu anc listl gte n,ghilea tbu ti ntwo’ be irneozgad aihlneg -- li’lt eb dagsiiozdern ianlh,eg wcihh seod ton earppa as omnrla uiests. zaniDe(oidgsr lheanig si reetbt ntah no hig,alen ubt iwhoutt a BM, eth nrergeitnega csell dtno’ vhae nay rnti”cdoei“ and efetroher n’cta reteors hte loarnm riatuet.rh)cce

drdoom  by "restorative" i mean healing which restores the previous (and normal) tissue architecture. for that to happen, you need an intact basement membrane! +2  
nwinkelmann  Yes, this a great summary to the post by @bubbles and the article he posted! Another way to think of the question is not, what causes repair, but what causes irreversible injury/fibrosis. That article explained an experiment that showed TGF-beta was necessary to initiate fibrosis, but if BM was intact and TGF-beta was removed, the fibrosis didn't persist, i.e. intact BM is protective against TGF-beta. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2645241/ +  



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I doulw thnik inoeolsrtu osveivln teh mest elscl tepy( II pen.cey)tuoms sI eth tnacti mbsteaen braemenm the waesrn uecsaeb ti limist adrse?p

aesalmon  I would also like to know if anyone can answer this question - I saw it as a Sattar "one day, one week, one month" kind of question. Its probably very simple but I still don't get it +  
bubbles  I posted a new comment explaining: basement membrane integrity is the strongest determinant of full fx recovery following pulmonary insult :) +3  
drdoom  You have to think about it this way: the basement membrane is the “scaffolding” on which [restorative] healing occurs. So, yes, stem cells (type II pneumocytes) would be involved in that healing process but they couldn’t restore the *normal* architecture (“no abnormalities”) without the ‘skeleton’ of the basement membrane telling them where to go, in what direction to grow, which way is “up”, etc. If the basement membrane is destroyed, you can still get healing, but it won’t be organized healing -- it’ll be *disorganized* healing, which does not appear as normal tissue. (Disorganized healing is better than no healing, but without a BM, the regenerating cells don’t have any “direction” and therefore can’t restore the normal architecture.) +7  
nwinkelmann  Yes, this a great summary to the post by @bubbles and the article he posted! Another way to think of the question is not, what causes repair, but what causes irreversible injury/fibrosis. That article explained an experiment that showed TGF-beta was necessary to initiate fibrosis, but if BM was intact and TGF-beta was removed, the fibrosis didn't persist, i.e. intact BM is protective against TGF-beta. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2645241/ +  



 +0  upvote downvote
submitted by ls3076(61),
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cna anyone ixpalen yhw D() esilapatam si toicre?rcn

angelaq11  because metaplasia would be a transformation of the normal architecture of the respiratory epithelium to one that does not belong there, in response to chronic irritation. This woman had pneumococcal pneumonia that was correctly (and I dare say promptly) treated, so she suffered an acute rather than a chronic insult. +  
blueberrymuffinbabey  because metaplasia isn't how the normal healing/regeneration response happens in the alveoli. the type 2 pneumocytes serve as stem cells/precursors to both type 1 and 2 pneumocytes so the regeneration is not metaplasia. +1