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NBME 22 Answers

nbme22/Block 4/Question#47 (46.3 difficulty score)
A 56-year-old woman comes to the physician ...
Maintenance of basement membrane integrity🔍
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 +12 
submitted by bubbles(63),
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meentsaB meamebnr eyritnitg is eht eatirdtmnen fo full glun yrcrevoe oiwfgllno umnyoalpr n.tsliu

m:uraySm

)1( sols of bemeasnt mrbeanem geiityrtn is tircical in drieeingtnm the iotnp“ of no ,untrre” adn sticotnreub ot eth liaynitib to eitarsesbhl mlnora glnu acecethrtuir ithw intomrpoo fo fi;osisbr

()2 sslo of elipeitlha ,elslc lohenildate el,lsc dna bneastem nemrbaem ttrigeyin ni suaul aseittrtilni aeiupnonm iaoetcadss twih ihpcitaido lmyoaunpr rssibfoi lesda ot deyosrtde ugnl ciatetcruehr nad eleaprput oirsbis;f

)3( fanrnsmgtroi wrtohg arβo-fct is eensaysrc, utb ton nlyeiret eiscinff,tu to pmeroto nretpaenm ioirb;ssf

4)( trietnsesp aitiunn//iritegrtjrnnya si alitrcic ofr eth gaipaortpon of rfsoibi;s

)(5 dotpiichai pounyralm ofirbssi si an xamlepe of a opcessr etledar to the eiptecesnsr of na n,(”ntgs“iae) hirccon in,nlmtioaamf dan osfbrsi;i nda

6)( ueqiun lecsl era aricictl lrlulcae seaylrp ni het alreutngoi fo sbf.ioisr

inoic:at twtwhMs/s2tnc.Pmthmcbniw1p/4i.v56p/.galCr/c2/4nie/l.:o

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 
submitted by drdoom(686),
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uoY eahv to htikn buoat it iths yaw: the smeetban mnbmreea is het fnsa”l“dgcoif no whhci vaeoretrtsi][ nighlea co.rcsu ,oS ys,e emst lcsel tp(ye II pet)yoncsume uwlod be ivlnovde ni thta iegnlah osrepcs tbu yhet cl’nuotd setreor teh omrnal tcahcireuter o(“n asbnie)o”rilmta uhittwo eth el’nekos‘t of eth neastbme marnebem gitnell ehmt weehr ot ,go in hawt neioritcd to ,wrgo ihwhc way si ,”u“p e.ct If hte nbemstae anbermem is odetsdre,y oyu nac tsill egt n,iagehl tub ti wnot’ eb oizgdnear aignleh -- tlil’ be iazdorndiges gnlhe,ia chwhi does nto eparpa as lamnor .teussi (Ddrioizgaens enghial si eebttr ahnt on lienh,ga tub hutwoti a B,M the ageningtrree clsel ntd’o haev yan eni”dti“rco nad refheoter c’ant eoerrts eht onraml ecr.he)tarituc

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/ +  



 +1 
submitted by shaydawn88(8),
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I duolw thkni onilreosut snvevoli het emts lcles py(et II suoyentm.epc) sI het tcatin neatmebs mnaeermb eth esrnwa ueebacs ti sitlmi asdpe?r

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.) +8  
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 
submitted by ls3076(65),
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nac eoynna inepxal hwy ()D laamtpsiea si ioctcre?nr

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