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