8- Lumbar and Sacral Plexuses

iliohypogastric & ilioinguinal

what nerve?

-anterior ramus L1

-enter abdomen posterior to diaphragm and pass inferolaterally, anterior to quadratus lumborum

-pierce transversus abdominis near ASIS and pass through internal and external obliques to supply abdominal muscles and skin of the pubic and inguinal regionsterior to diaphragm and pass inferolaterally, anterior to quadratus lumborum

lumbar spinal nerves

-pass from spinal cord through the intervertebral foramen inferior to the corresponding vertebrae

-divide into dorsal (posterior) and ventral (anterior) rami

dorsal rami

-pass posteriorly to supply the deep back muscles and skin of the back

ventral rami

pass through the Psoas Major to supply the skin and muscles of most inferior trunk and lower limb

sympathetic

What kind of nerves are lumbar spinal nerves?

lumbar plexus

-Network of nerves in posterior part of Psoas Major, anterior to lumbar transverse processes

-Comprised of ventral rami of L1-L4 nerves

-All rami receive gray communicating branches from the sympathetic trunks --->post-ganglionic sympathetic fibers

transversus abdominis near ASIS and pass through IAO and EAO to supply abdominal muscles and skin of the pubic and inguinal regions

What areas do the the iliohypogastric and ilioinguinal nerves pierce?

ilioinguinal nerve in lumbar plexus

-anterior ramus L1

-enter abdomen posterior to diaphragm and pass inferolaterally, anterior to quadratus lumborum

-Pierce transversus abdominis near ASIS and pass through internal and external obliques to supply abdominal muscles and skin of the pubic and inguinal regions

genitofemoral nerve in lumbar plexus

-pierces anterior surface of psoas major and runs inferiorly along it

-lateral to common and external iliac arteries, it divides into femoral and genital branches

lateral femoral cutaneous nerve in lumbar plexus

-runs inferolaterally along the iliacus and enters the thigh posterior to the inguinal ligament

-supplies the skin on the anterolateral thigh

-sensory

femoral nerve in lumbar plexus

-emerges from lateral border of Psoas Major and innervates the iliacus

-passes deep to inguinal ligament to the anterior thigh

-motor innervation to hip flexors and knee extensors

-cutaneous sensation to anterior thigh

-gives off saphenous nerve

saphenous nerve- branch of femoral nerve, cutaneous to anterior/medial lower leg and foot

obturator nerve in lumbar plexus

-emerges from medial border of psoas major

-passes through the pelvis to medial thigh

-motor innervation to hip adductors

-cutaneous sensation to proximal medial thigh

lumbosacral trunk in lumbar plexus

-passes over ala (wings) of sacrum and descends into pelvis to help form the sciatic nerve and sacral plexus along with anterior rami S1-S4

femoral nerve, obturator nerve, lumbosacral trunk

Which three nerves in the lumbar plexus are the largest?

"I Twice Got Lost On Freeways"

How to remember the nerves of the lumbar plexus

sacral nerves

-innervate the pelvic structures and the pelvic part of the autonomic nervous system

-located on the posterolateral wall of the true (lesser) pelvis

-two main nerves: sciatic and pudendal

-most of the branches leave pelvis through the greater sciatic foramen

sciatic nerve in the sacral plexus

-most often passes through the greater sciatic foramen, inferior to piriformis, to enter gluteal region

-goes to posterior thigh

-motor only

pudendal nerve in the sacral plexus

-accompanies internal pudendal artery and leaves the pelvis through greater sciatic foramen between piriformis and coccygeus

-hooks around the ischial spine and sacrospinous ligament to enter perineum through the lesser sciatic foramen

-supplies skin and muscles of the perineum, including reproductive, urinary, and digestive tracts

-motor and sensory to pelvic floor

anterior rami S2-S4

Nerve roots of pudendal nerve

ventral rami L4, L5, S1, S2, S3

Nerve roots of sciatic nerve

anterior rami L4, L5

Nerve roots of lumbosacral trunk

anterior rami L2, L3, L4

Nerve roots of obturator nerve

anterior rami L2, L3, L4

Nerve roots of femoral nerve

anterior rami L2, L3

Nerve roots of lateral femoral cutaneous

anterior rami L1, L2

Nerve roots of genitofemoral nerve

anterior rami L1

Nerve roots of iliohypogastric nerve

anterior rami L1

Nerve roots of ilioinguinal nerve

superior gluteal nerve in sacral plexus

-leaves the pelvis through the greater sciatic foramen with the superior gluteal vessels, superior to the piriformis

-supplies glute med, glute min, and tensor fascia latae

anterior rami L4, L5, S1

Nerve roots of superior gluteal nerve

inferior gluteal nerve in sacral plexus

what nerve?

-leaves the pelvis through the greater sciatic foramen with the inferior gluteal vessels, inferior to the piriformis and superficial to sciatic nerve

-breaks up into several branches that supply the glute max

Anterior rami L5, S1, S2

Nerve roots of inferior gluteal nerve

articular branches to hip joint and muscular branches to knee flexors (HS) and all muscles in leg and foot

Distribution of sciatic nerve

abdominal muscles and skin of pubic and inguinal regions

Distribution of iliohypogastric nerve

abdominal muscles and skin of pubic and inguinal regions

Distribution of ilioinguinal nerve

anterior psoas major; divides into femoral and genital branches

Distribution of genitofemoral nerve

supplies skin on anterolateral thigh (sensory only)

Distribution of lateral femoral cutaneous nerve

motor to hip adductors; cutaneous sensation to proximal medial thigh

Distribution of obturator nerve

motor to hip flexors and knee extensors; cutaneous to anterior thigh

Distribution of femoral nerve

perineum, sensory to genitalia; muscular to perineal muscles

Distribution of pudendal nerve

glute med, glute min, tensor fascia latae

Distribution of superior gluteal nerve

glute max

Distribution of inferior gluteal nerve

lateral cutaneous branch of subcostal nerve

#16; T12

lateral femoral cutaneous nerve

#4

anterior cutaneous branches of femoral nerve

#1

femoral branch of genitofemoral nerve

#7

genital branch of genitofemoral nerve

#10

ilioinguinal nerve

cutaneous branch of obturator nerve

L

saphenous nerve

superior gluteal cutaneous (clunial nerves)

posterior rami; #1

lateral cutaneous nerve of thigh

posterior cutaneous nerve of thigh

S1-S3

L2 dermatome

L1 dermatome

L3 dermatome

L4

L5 dermatome

S1

what dermatome?