Sacral Plexus Lecture Notes

Overview

• Continuation of discussion from cervical, brachial, and lumbar plexuses
• Importance of watching lumbar plexus lecture for context

Sacral Plexus Origins

• From spinal nerves L4, L5, and S1–S5
• Includes coccygeal nerve (C1)

Key Nerves from Sacral Plexus

Sciatic Nerve

• Major nerve from sacral plexus
• Formed by branches from L4, L5, S1, S2, and S3
• Important for motor and sensory functions
• Splits into the anterior (tibial nerve) and posterior (common fibular nerve) divisions near the knee
• Clinical relevance: Sciatic nerve pain, often due to herniated disks

Superior Gluteal Nerve

• Formed from L4, L5, and S1
• Motor nerve
• Supplies: Gluteus medius and gluteus minimus (hip abductors)

Inferior Gluteal Nerve

• Formed from L5, S1, and S2
• Supplies: Gluteus maximus (hip extensor and lateral rotator)

Obturator Internus Nerve

• Formed from L5, S1, and S2
• Supplies: Obturator internus and superior gemellus (lateral rotators of the hip)

Posterior Cutaneous Nerve

• Formed from S1, S2, and S3
• Sensory nerve
• Supplies: Inferior buttocks, posterior thigh, popliteal region, calf, and heel

Pudendal Nerve

• Formed from S2, S3, and S4
• Motor functions: External anal sphincter, external urethral sphincter
• Sensory functions: Entire perineum (scrotum, penis, anus for males; clitoris, labia majora, perineum for females)

Nerve to Piriformis

• Formed from S1 and S2 (posterior division)
• Supplies: Piriformis muscle (lateral rotator of the hip)

Coccygeal Plexus

• Formed from S4, S5, and Coccygeal 1
• Supplies: Cutaneous area around the coccyx

Clinical Correlations

Sciatica

• Caused by compression of the sciatic nerve (common cause: herniated disk)
• Results in pain, numbness, tingling in posterior and lateral legs
• Treatments: Rest, NSAIDs, physical therapy, possible surgery

Hilton's Law

• States that a nerve supplying muscles crossing a joint also supplies the skin around that joint

Summary of Nerve Branches

• Superior Gluteal Nerve: L4, L5, S1
• Inferior Gluteal Nerve: L5, S1, S2
• Sciatic Nerve: L4, L5, S1, S2, S3 (Anterior division: L4–S3; Posterior division: L4–S2)
• Pudendal Nerve: S2, S3, S4
• Posterior Cutaneous Nerve: S1, S2, S3
• Nerve to Piriformis: S1, S2
• Obturator Internus Nerve: L5, S1, S2
• Coccygeal Plexus: S4, S5, C1

Conclusion

• Comprehensive study of the sacral plexus
• Clinical importance of nerve damage and irritations

Key Takeaways

• Motor and sensory functions of various nerves
• Clinical conditions and their impact on daily life