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NBME 24 Answers

nbme24/Block 4/Question#35

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Basal keratinocyte:suprabasal keratinocyte

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 +5  upvote downvote
submitted by lsmarshall(215),

"Desmosome (Macula adherens) - A cell-to-cell connection that provides structural support with intermediate filaments, particularly in tissues that undergo mechanical stress (e.g., skin, gastric tissue, bladder). Connects keratinocytes in the stratum spinosum of the epidermis." - AMBOSS

sympathetikey  This is why I was looking for some answer indicating keratinocytes in the stratum spinosum...instead they just gave a bunch of bs choices. +9  
roygbiv  I'm confused because I also know that S. aureus cleaves desmoglein in the stratum granulosum, so why is it specifically this answer? +  
duat98  desomosomes connects cells to cells. hemidesmosome connects cells to basement membrane. +  




Stupid question, honestly just take your best guess and move on lol.

seagull  ░░░░░░░░░░░█▀▀░░█░░░░░░ ░░░░░░▄▀▀▀▀░░░░░█▄▄░░░░ ░░░░░░█░█░░░░░░░░░░▐░░░ ░░░░░░▐▐░░░░░░░░░▄░▐░░░ ░░░░░░█░░░░░░░░▄▀▀░▐░░░ ░░░░▄▀░░░░░░░░▐░▄▄▀░░░░ ░░▄▀░░░▐░░░░░█▄▀░▐░░░░░ ░░█░░░▐░░░░░░░░▄░█░░░░░ ░░░█▄░░▀▄░░░░▄▀▐░█░░░░░ ░░░█▐▀▀▀░▀▀▀▀░░▐░█░░░░░ ░░▐█▐▄░░▀░░░░░░▐░█▄▄░░░ ░░░▀▀▄░░░░░░░░▄▐▄▄▄▀░░░ THis Question ░░░░░░░░░░░░░░░░░░░░░░░ +2  




Basically asking if you know Pemphigus Vulgaris. Separation of suprabasilar epidermis, intact basal keratinocytes vs Bollous pemphigoid--> includes separation of basal layer

subclaviansteele  This how I thought of the question...Classic histology photo of the "tomb stone" row of basal cells and the lifted keratinocytes. +  




After some research this is why the other answers are incorrect:

  1. basal keratinocyte & lamina lucida
  2. Incorrect b/c lamina lucida is a component of the basement membrane which is found between the epithelium and underlying connective tissue (e.g., epidermis and dermis of the skin).
  3. It is a roughly 40 nanometre wide electron-lucent zone between the plasma membrane of the basal cells and the (electron-dense) lamina densa of the basement membrane. (WIKI)
  4. basal keratinocyte attaches to the basement membrane using hemidesmosome

  5. Granular keratinocyte & stratum corneum

  6. Stratum lucidum separates these two layers.
  7. there are no desmosome that connect these two layers
  8. Image for reference

  9. Lamina lucida & Lamina densa -- click for image

  10. both are part of the basement membrane and not the epidermis

  11. Melanocyte & basal kertinocyte --- click for image

  12. are both connected to eachoter via E-cadherins
  13. it is probably the damage to this connection that might lead to melanoma




After some research this is why the other answers are incorrect:

Basal keratinocyte & lamina lucida

  • Incorrect b/c lamina lucida is a component of the basement membrane which is found between the epithelium and underlying connective tissue (e.g., epidermis and dermis of the skin).
  • It is a roughly 40 nanometre wide electron-lucent zone between the plasma membrane of the basal cells and the (electron-dense) lamina densa of the basement membrane. (WIKI)
  • basal keratinocyte attaches to the basement membrane using hemidesmosome

Granular keratinocyte & stratum corneum

  • Stratum lucidum separates these two layers.
  • there are no desmosome that connect these two layers
  • Image for reference

Lamina lucida & Lamina densa -- click for image

  • both are part of the basement membrane and not the epidermis

Melanocyte & basal kertinocyte --- click for image

  • are both connected to eachoter via E-cadherins
  • it is probably the damage to this connection that




Blistering diseases such as pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are autoimmune diseases in which auto-antibodies target desmogleins.

  • PV is caused by circulating autoantibodies (IgG) that target Dsg3 (Desmoglein 3) and sometimes Dsg1.
  • PV is manifested by suprabasal acantholysis, or blisters in the mucous membrane and blisters in the epidermis.
  • PF patients have autoantibodies that target Dsg1 with superficial blisters on the epidermis with no mucous membrane issues.
  • Both disease result in a loss of keratinocyte adhesion.
  • Pemphigus can also be caused by a bacterial infection: bullous impetigo is an infection caused by a staphylococcus bacterium that releases a toxin that cleaves the Dsg1 extracellular domain.




Desomosmes by function interconnect keratinocytes in the stratum spinosum - startum spinosum is the suprabasal layer. Exclude option: a) Lucida is too high ; not in continuation with basal layer c) Corneum is even higher, Granulosum and Corneum aren't n continuation d) Lamina dens (BM) and lamina lucida not keratinocytes and not in continuation either e) Melanocyte are in the basal layer; it is not a keratinocyte

b) is the only option that makes sense based on histology and also the only option that speaks about inter-keratinocyte linkage





 +0  upvote downvote
submitted by rocmed(-1),

Desmoglein: Component of desmosomes, which connect keratinocytes in the stratum spinosum - FA 2018, p.467, Pemphigus Vulgaris

By this I can only assume that they mean that desmoglein connects keratinocytes to EACH OTHER, hence why the other options connecting keratinocytes to other structures are incorrect

charcot_bouchard  The epidermis primarily consists of keratinocytes[4] (proliferating basal and differentiated suprabasal), which comprise 90% of its cells. You are right. both are keratinocyte +  




Why is basal keratinocyte : suprabasal keratinocyte the cell junction that’s most likely to be affected? Is it because it’s the only answer that lists a junction between two keratinocytes?

sattanki  Not too sure on this one, but I interpreted the basal keartinocyte:suprabasal keratinocyte as the stratum spinosum region, which is known to have the most desmosomes. +  




Desomosmes by function interconnect keratinocytes in the stratum spinosum - startum spinosum is the suprabasal layer. Exclude option: a) Lucida is too high ; not in continuation with basal layer c) Corneum is even higher, Granulosum and Corneum aren't n continuation d) Lamina dens (BM) and lamina lucida not keratinocytes and not in continuation either e) Melanocyte are in the basal layer; it is not a keratinocyte

b) is the only option that makes sense based on histology and also the only option that speaks about inter-keratinocyte linkage