NBME Explanations

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NBME Explanations

NBME 17 Questions and Answers

Discussion in 'USMLE Step 1' started by orthopod, May 24, 2015.

  1. PNWMD

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    Block 3 Part 1 #5

    The correct answer was the one about intact basement membranes. As with most tissues, complete regeneration is possible as long as the basement membrane stays intact, otherwise scarring.
     
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  2. PNWMD

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    Block 4 Part 1 #17

    I think this one can be solved if you look at the homunculus for the somatosensory cortex and know where the region that deals with the foot is.
     
  3. PNWMD

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    Block 4 Part 1 # 21

    There is no way levator labii superioris is the correct answer. The image was of bilateral mandibular fractures on either side of the arch, I am positive the correct answer was injury to the inferior alveolar nerve.
     
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  4. PNWMD

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    Block 4 Part 2 # 46

    The vignette is definitely describing endometriosis with chocolate cysts. Retroflexed uterus + painful menses + infertility = endometriosis.
     
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  5. PNWMD

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    Multiply the serum concentration by the volume of distribution to get the total amount of drug in the body at the time of the lab draw:
    0.3 units of drug x 200L = 60 units/L drug in the whole body

    6 hrs since first dose / 2hrs per half life = 3 half lives elapsed

    Working backwards through the half lives to original concentration: 60-->120-->240-->480 (each arrow represents one half life)
     
  6. Mohammad Taha

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    Thanks PNWMD!
     
  7. Rajiv Chibundu

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    I selected TSH, and the question didn't appear among the ones I failed
     
  8. Rajiv Chibundu

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    Block 3: #5; this question didn't appear among the questions I failed, and I know I didn't select "metaplasia of mesenchymal cells to pneumocytes", can't remember the options

    I can remember the rest I selected, that didn't appear among my failed questions, even though I may paraphrase

    Block 4: #13; peroxidase mediated membrane damage
    Block 4: #19; most people find it difficult to adhere to a routine, how did you do
    Block 4: #21; inferior alveolar nerve
    Block 4: #26; TSH
     
  9. ymma

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    its free t4, because estrogen [she's preggo] augments binding protein, so you have to make sure the FREE t4 is the one thats elevated
     
  10. mahmoud

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    omeprazole decrease the efficacy of itraconazole because PPI will decrease itraconazole absorption
     
  11. mahmoud

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    block 3- question 9
    the right amswer is increase blood HCO3 because the patient has respiratory acidosis( CO2 retention) with compensatory renal metabolic alkalosis ( increase renal HCO3 absorption) so blood HCO3 will increae
     
  12. mahmoud

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    I agree- I choose that answer and it is correct
     
  13. mahmoud

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    can anyone explain to me why the correct answer to is this question is (25% )

    9. 45yo woman follow-up exam after 8 weeks tamoxifen therapy for estrogen- and progesterone-positive invasive ductal carcinoma of breast. 50yo sister also hormone-sensitive breast cancer. Physical exam normal. Serum decreased concentrations of endoxifen, active metabolite of prodrug tamoxifen. Genetic analysis shows homozygous cytochrome P450 2D6*4 alleles. Likelihood patient's sisters has same alleles?
    - 25%
     
  14. Jill_Aileen

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    Block 2 Part 1 #20

    I think the answer should be "they must be given decreased doses of 6-MP." What do you think?

    6-MP is broken down by the 3 pathways shown in the picture to form:
    1) oxidized metabolites by XO
    2) 6-MMP by TPMT
    3) 6-TGN
    The question tells you that the 6-TPMT byproduct is responsible for drug efficacy, but that it is also toxic at high levels. So if a patient taking 6-MP has less TPMT enzyme, then more of the drug will be pushed toward the other 2 pathways. The answer I put was to inject the person w/ XO (which I assume would prevent any 6-MP from being converted to 6-TGN. I was thinking only about the toxicity of 6-TGN, and ignoring its role in drug efficacy). NBME marked that wrong. So considering that you want SOME of the 6-MP to be converted to 6-TGN, I think it should be "give decreased doses of 6-MP."
     
  15. smile

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    maintenance of basement membrane integrity
    because of intact B.M. the organ infrastructure is maintained.
     
  16. smile

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    T10
     
  17. smile

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    i guess its membrane damage due to free radicals.
     
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  18. Lenka Penka

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    Thants right, here's a quote from pubmed article:
    Due to the suppression of gastric acid secretion, they (PPIs) can significantly alter the intragastric pH conditions and are thus likely to affect the bioavailability of coadministered drugs requiring an acidic gastric environment for dissolution and subsequent absorption. Among these drugs can be found itraconazole, a poorly soluble triazole-type antifungal compound. Based on observations reported in the literature, gastric pH alterations due to the coadministration of PPIs or acidic beverages can significantly decrease (PPI) or increase (e.g., Coca-Cola) the bioavailability of this compound.
    https://www.ncbi.nlm.nih.gov/pubmed/23947755
     
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  19. Lenka Penka

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    These are the structures depicted:
    a- capillary endothelial cell
    b- erythrocite in capillary
    c- type I pneumocyte
    d- type II pneumocyte- correct answer (produces surfactant)
    e- macrophage

    This illustration is helpfull-
     
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  20. Lenka Penka

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    Explanation:
    The description is of contact dermatitis.
    Plant-related contact dermatitis most commonly occurs from exposure to poison ivy, poison oak, or poison sumac. The pruritic rash is typically erythematous with papular lesions in a linear pattern.
    source:
    http://www.aafp.org/afp/2009/0515/p901.html
     
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