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NBME 20 Answers

nbme20/Block 4/Question#47 (reveal difficulty score)
A 61-year-old man has erectile dysfunction ...
Area labeled โ€˜Dโ€™ (Corpus cavernosum) ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags: anatomy pharm

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submitted by โˆ—neovanilla(57)

A = Maybe the superficial dorsal vein

B = Areolar tissue

C = Urethra (surrounded by corpus spongiosum)

D = Corpus cavernosum (correct answer)

Sildenafil increases blood flow to the penis by dilating the corpus cavernosum (increased NO via inhibition of PDE5 --> cGMP --> smooth muscle relaxation). It doesn't actually affect the blood vessels supplying the corpus cavernosum, I believe

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mangotango  This pathway causes relaxation of vascular smooth muscle so it causes vasodilation and increased blood flow to the corpus cavernosum, causing an erection. +2

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submitted by โˆ—xxabi(293)

PDE-5 inhibitors (e.g. sildenafil, tadalafil) are indicated for ED by way of increasing blood flow in the corpus cavernosum (labeled D) of the penis

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dulxy071  I believe technically the answer would not be (B) as the corpus cavernosum isn't ACTED ON by PDE inhibitors ( per the words used in the question ) but rather simply fills as a result of PDE inhibitors acting on the internal pudis artery among many others to allow more blood flow into the corpus cavernosum for an erection +4

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submitted by โˆ—calvin_and_hobbes(2)

Due to its pink staining, I thought B was smooth muscle surrounding the corpus cavernosum. But I suppose that the cells composing the CC are contractile by themselves? And my assumption would make the penis a giant muscle โ€” which it most certainly is not...

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submitted by โˆ—ley(1)

cGMP is broken down by phosphodiesterase so phosphodiesterase inhibitors will cause more cGMP and more vasodilation.

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