Nerves of the Pelvis Flashcards
What forms the sacral plexus?
- lumbosacral trunk (L4, L5): part of the lumbar plexus
2. anterior primary rami of S1-S4
Where does the sacral plexus lie?
primarily on the anterior surface of piriformis
Where do the anterior primary rami of S1-S4 enter the pelvis?
through the anterior sacral foramina
What are the branches of the sacral plexus that supply the buttock and lower limb?
- superior gluteal nerve (L4-S1)
- inferior gluteal nerve (L5-S2)
- sciatic nerve (L4-S3)
- nerve to obturator internus muscle (L5-S2)
- nerve to quadratus femoris muscle (L5-S1)
- posterior cutaneous nerve of the thigh (S1-S3)
Describe the superior gluteal nerve.
- from L4-S1
- exits the pelvis through the greater sciatic foramen superior to piriformis
- supplies the gluteus medius, gluteus minimus, and tensor fasciae latae muscles
- impingement or injury results in trendelenberg’s gait
- anterior gluteal muscles prevent pelvis from slumping to unsupported side during gait
Describe the inferior gluteal nerve.
- from L5-S2
- exits the pelvis through the greater sciatic foramen inferior to piriformis
- supplies the gluteus maximus
- gluteus maximus functions in trunk control and standing from a seated position
Describe the sciatic nerve.
- from L4-S3
- the largest nerve in the body
- exits the pelvis through the greater sciatic foramen inferior to piriformis
- supplies numerous structures in the lower extremity
- impingement causes sciatica
Describe the nerve to obturator internus muscle.
- from L5-S2
- exits the pelvis through the greater sciatic foramen inferior to piriformis
- then enters the perineum through the lesser sciatic foramen
- supplies the obturator internus and superior gemellus
Describe the nerve to the quadratus femoris muscle.
- from L5-S1
- exits the pelvis through the greater sciatic foramen inferior to piriformis
- supplies the quadratus femoris and inferior gemellus
Describe the posterior cutaneous nerve of the thigh.
- from S1-S3
- exits the pelvis through the greater sciatic foramen inferior to piriformis
- sensory to part of the gluteal region and perineum
What are the branches of the sacral plexus which supply the pelvis?
- nerve to piriformis muscle (S1, S2)
- nerves to levator ani and coccygeus muscles (S3, S4)
- nerve to external anal sphincter muscle (S4)
- pudendal nerve (S2-S4)
Describe the nerve to piriformis.
- from S1 and S2
- supplies the piriformis
- impingement leads to Piriformis Syndrome, which contributes to Sciatica
Describe the nerves to levator ani and coccygeus.
- from S3 and S4
- supply levator ani and coccygeus
- impingement may affect:
1. integrity of the pelvic floor
2. urinary continence
3. fecal continence
4. parturition
Describe the nerve to the external anal sphincter.
- from S4
- supplies the external anal sphincter
- impingement may affect fecal continence
Describe the pudendal nerve.
- from S2-S4
- exits the pelvis through the greater sciatic foramen inferior to piriformis
- enters the perineum through the lesser sciatic foramen, traveling in the pudendal canal
- gives off important branches to the perineum
- supplies the external genitalia and underlying musculature; also sensory
- impingement may affect sexual function
What are the routes by which sympathetic fibers reach the pelvis?
- the downward continuation of the sympathetic trunk
2. the downward continuation of the aortic plexus, as the superior hypogastric plexus
What is the ganglion impar?
the union of the left and right sympathetic trunks in front of the coccyx
What are the components of the pelvic autonomic system?
- superior hypogastric plexus
- left and right hypogastric nerves
- left and right inferior hypogastric plexuses (pelvic plexuses)
- sacral splanchnic nerves
- pelvic splanchnic nerves (nervi erigentes)
Describe the superior hypogastric plexus.
- the downward continuation of the aortic plexus below the bifurcation of the abdominal aorta
- contains mainly:
1. sympathetic fibers from the lumbar splanchnic nerve
2. visceral afferent fibers
Describe the left and right hypogastric nerves.
- formed by the superior hypogastric plexus
- two long, narrow nerve plexuses which connect the superior hypogastric plexus to the inferior hypogastric plexus
Describe the left and right inferior hypogastric plexuses (pelvic plexuses).
- formed by the union of the hypogastric, pelvic splanchnic, and sacral splanchnic nerves
- they contain:
1. sympathetic fibers
2. parasympathetic fibers
3. visceral afferent fibers
What do the inferior hypogastric plexuses give rise to?
subsidiary plexuses which supply pelvic viscera
Describe the sacral splanchnic nerves.
preganglionic sympathetic nerves which arise from the sympathetic trunk and synapse in the inferior hypogastric plexus
Describe the pelvic splanchnic nerves (nervi erigentes).
- parasympathetic nerves which arise from the sacral segments of the spinal cord (S2-S4)
- they contribute to the formation of the inferior hypogastric plexuses
- supply pelvic viscera
