share email twitter ⋅ join discord whatsapp(2ck)
free120  nbme24  nbme23  nbme22  nbme21  nbme20  nbme19  nbme18  nbme17  nbme16  nbme15  nbme13 

NBME 21 Answers

nbme21/Block 4/Question#23 (58.9 difficulty score)
An investigator is studying the regulation of ...
Intravenous infusion of 0.9% saline for 5 minutes🔍

Login to comment/vote.

submitted by hayayah(1057),
unscramble the site ⋅ remove ads ⋅ become a member ($39/month)

mphLy wofl aetr is uslluya ow.l It is iuneefdcln pimlirary yb the tare fo mlpyh ari.mtnofo roF ,xepaeml fi oolbd pcyaralil eusreprs si adrnicsee by rilatrea diiaanolvsot ro ueosvn ncortscit,noi the wfol aret fo mpylh r.snasicee o,lsA eth wolf tear is actefdef yb omesisconpr fo pahclysitm yb rttcncoonai of eginibhgonr ursmcateluu nad by eaigntev ctrrancaihiot errsepus igebhra)nt.(

tntisielrtaI sepesrur o(s urepessr ni eht EF,C hhciw dluow rianecse fi nivge VI ni)slea nda lymhp lfow are iiolsvtyep .aedtrel A lsmla irceasen ni rliaentisitt mulevo aetglry icarsnsee tsi uep,rerss irnopmogt hylpm lfwo that cast to eroetsr hte ltsiteitnrai omulve ot a.mnrol

rmoe on hist tpo:ci :h/gv/oNt.5s./opt483nKniwshwmcb4l/ib..wBo/kn

linwanrun1357  Do not understand the breathing (choice C and D) breath in and out are different? +  
khanhluong  I don't know if it's correct or not but how I approached C & D was that they both cause vasoconstriction in the arterioles (because this is the lung where hypoxia causes vasoconstriction), which decreases hydrostatic pressure through the capillaries and eventually decreases lymph flow. Maybe I completely got this question right for wrong reason, but I felt that it works with all of the answers. For F) I was thinking that it would cause increased capillary oncotic pressure which causes more fluid to go into the capillary than into the lymph vessels... Here's a picture: +5  

submitted by andro(173),

First Point : Lymph forms at the Capillary level of blood vessels ( as this is where fluid moves in and out of vessels along with metabolites and nutrients ) .

The function of lymph is to return excess proteins and interstitial fluid back to the bloodstream ( Recall Lymph eventually drains into the large veins)

Second Point : We may increase lymph either by increasing 1. the rate at which we form it . 2. Decreasing the rate of drainage ( i.e - obstructing lymph vessels )

To increase lymph formation we have to increase the rate at which fluid filters out of the capillaries . This can be done by altering Starlings forces in the capillary

  • Increasing hydrostatic pressure
  • Decreasing Oncotic pressure

Going through the options
Option A : Endothelin will cause vasoconstriction of Pulmonary artery .This is precapillary meaning we will have less blood/ fluid getting to the capillaries - decreased hydrostatic pressure and decreased lymph formation
Option B : Constriction of pulmonary artery again
Option C and D : lead to the physiologic response of hypoxic vasoconstriction
Option E : Increased oncotic pressure decreases the amount of fluid moving out of capillaries

lovebug  now I understand~~!! THX :) +1  
limberry  I believe you mean "Option F: Increased oncotic pressure decreases the amount of fluid moving out of capillaries" instead of Option E, right? +  

submitted by drdoom(819),
unscramble the site ⋅ remove ads ⋅ become a member ($39/month)

iatotVncsicosorn rorannig(w of a e)utb iwll cuesa het flwo taer to enrcesai otrghhu htta b,ute ichwh escrsadee ddlaoatar/wiur s.ruserpe eTh rtesaf a idulf esmov trhhuog a e,btu hte ssel twru”o“da feorc it t.rxese si(hT is nknwo sa teh netiurV eftfec.)

hungrybox  not seeing how this is relevant +8  
sympathetikey  He's showing how A & B are incorrect @hungrybox +7  
nerdstewiegriffin  what a moron @hungrybox is !! +2  
leaf_house  MCAT flashbacks on this image +1  

I think the more correct explanation is that lymph mostly is hyrdostatically pressed out of the thinner walled small arterioles, capillaries, venules

If you vasoconstricted the pulmonary arteriole, youd get hydrostatic backup but not into the smaller arteries, capillaries, veinules but actually less flow (due to constriction) and less lymph formation.

+/- jackie_chan(16),

submitted by d_holles(173),
unscramble the site ⋅ remove ads ⋅ become a member ($39/month)

%20 aunlmbi si EcHonYiRtP dna euassc wgianrd of fldui uot fo eth uimritttnes dna inot eth doolb.

"mAbinlu Hn(a)mu 2%0 si ieiadctdn in teh eycneremg aeenrtmtt fo lyaoivhoepm tihw ro itwohut .kshco tIs eeiscsvftenef in gensrirve mlevyophioa nedsdep lgrelay puno its ilyitba ot dwra nlititestiar dufil tnoi the niiarcuc.lto tI is omst feiecevft in itsnptea owh rae llwe ryhetdd.a Wenh odobl omvelu dcftiei is the eultrs fo reh,agorhem aptmeblcoi der bdolo lcesl ro helwo doblo dlusoh eb rdaiesiemdnt sa ucqkily as pie"lsso.b


submitted by assoplasty(91),
unscramble the site ⋅ remove ads ⋅ become a member ($39/month)

aicittVncsronoos sesrceeda lobod owfl dna tuhs eceaesdrs oayhrttcdis erusre.sp Sesme toucren vnttieuii btu I adh to loko htis up frtae I otg it wrng,o