Pelvic floor musculature, perineal spaces, and innervation tested on USMLE Step 1.
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- What are the three muscles that make up the levator ani?
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Puborectalis, pubococcygeus, and iliococcygeus.- Which levator ani muscle forms a U-shaped sling around the anorectal junction?
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Puborectalis.- What nerve innervates the levator ani muscle?
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The nerve to levator ani (S3-S4), with additional contribution from pudendal nerve branches.- Which muscle, together with the levator ani, forms the pelvic diaphragm?
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Coccygeus.- What spinal nerve roots supply the coccygeus muscle?
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S4 and S5.- What spinal nerve roots give rise to the pudendal nerve?
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S2, S3, and S4.- Through which foramen does the pudendal nerve leave the pelvis to enter the gluteal region?
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Greater sciatic foramen.- Through which foramen does the pudendal nerve re-enter to reach the perineum?
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Lesser sciatic foramen.- What is the name of the canal that carries the pudendal nerve along the lateral wall of the ischioanal fossa?
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Pudendal canal (Alcock's canal).- What bony landmark is palpated to guide a pudendal nerve block during labor?
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Ischial spine.- What are the three terminal branches of the pudendal nerve?
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Inferior rectal nerve, perineal nerve, and dorsal nerve of the penis/clitoris.- Which pudendal nerve branch innervates the external anal sphincter?
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Inferior rectal nerve.- Which artery travels alongside the pudendal nerve through the pudendal canal?
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Internal pudendal artery.- What bony and ligamentous landmarks form the diamond-shaped boundary of the perineum?
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Pubic symphysis, ischiopubic rami, ischial tuberosities, sacrotuberous ligaments, and coccyx.- An imaginary line between the ischial tuberosities divides the perineum into what two regions?
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The urogenital triangle (anterior) and the anal triangle (posterior).
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