Sacral Plexus Flashcards

Explore sacral plexus anatomy, including its spinal roots, pelvic relationships, major nerve branches, motor and sensory supply, and clinical relevance.

Card 1 of 30Question

Which spinal nerve levels contribute to the sacral plexus?

The anterior rami of L4 to S4, including the lumbosacral trunk.

In This Section

1. Which spinal nerve levels contribute to the sacral plexus?

The anterior rami of L4 to S4, including the lumbosacral trunk.

2. Which spinal nerve roots form the lumbosacral trunk?

Part of the anterior ramus of L4 and the anterior ramus of L5.

3. Where is the sacral plexus located?

On the posterolateral wall of the pelvis, anterior to the piriformis muscle.

4. Which muscle forms the principal muscular bed of the sacral plexus?

Piriformis.

5. Which pelvic blood vessels lie anterior to the sacral plexus?

Branches of the internal iliac vessels.

6. Which major nerve is formed by the anterior rami of L4 to S3?

The sciatic nerve.

7. What are the two major components of the sciatic nerve?

The tibial and common fibular components.

8. Which divisions of the sacral plexus form the tibial component of the sciatic nerve?

The anterior divisions of L4 to S3.

9. Which divisions form the common fibular component of the sciatic nerve?

The posterior divisions of L4 to S2.

10. Through which opening do most major branches of the sacral plexus leave the pelvis?

The greater sciatic foramen.

11. Which major nerve normally exits the pelvis inferior to piriformis?

The sciatic nerve.

12. Which nerve exits the pelvis superior to piriformis?

The superior gluteal nerve.

13. Which spinal nerve roots form the superior gluteal nerve?

L4, L5, and S1.

14. Which muscles receive motor innervation from the superior gluteal nerve?

Gluteus medius, gluteus minimus, and tensor fasciae latae.

15. Which spinal nerve roots form the inferior gluteal nerve?

L5, S1, and S2.

16. Which muscle is innervated by the inferior gluteal nerve?

Gluteus maximus.

17. Which sacral plexus nerve supplies cutaneous sensation to much of the posterior thigh?

The posterior femoral cutaneous nerve.

18. Which spinal nerve roots form the posterior femoral cutaneous nerve?

S1, S2, and S3.

19. Which nerve supplies obturator internus and superior gemellus?

The nerve to obturator internus, arising from L5 to S2.

20. Which nerve supplies quadratus femoris and inferior gemellus?

The nerve to quadratus femoris, arising from L4 to S1.

21. Which spinal nerve roots typically form the nerve to piriformis?

S1 and S2.

22. Which nerve from the sacral plexus is the principal somatic nerve of the perineum?

The pudendal nerve.

23. Which spinal nerve roots form the pudendal nerve?

S2, S3, and S4.

24. How does the pudendal nerve enter the perineum?

It exits through the greater sciatic foramen and reenters through the lesser sciatic foramen.

25. Which ligament does the pudendal nerve pass near as it curves around the ischial spine?

The sacrospinous ligament.

26. Which nerve roots provide parasympathetic fibers to pelvic organs through the pelvic splanchnic nerves?

S2, S3, and S4.

27. What clinical sign may result from injury to the superior gluteal nerve?

A positive Trendelenburg sign due to weakness of the hip abductors.

28. What movement becomes particularly difficult following inferior gluteal nerve injury?

Powerful hip extension, such as rising from a chair or climbing stairs.

29. What motor deficits can occur with a severe sciatic nerve injury?

Weakness of knee flexion and loss or impairment of most movements at the ankle and foot.

30. Which anatomical variation can affect the relationship between the sciatic nerve and piriformis?

The common fibular component may pass through or above piriformis instead of below it.