Lumbosacral Plexus

Question 1

Lumbar Plexus

Answer 1

Anterior Rami

L1-L4

Some contribution from T12 and part of L4

Emerging position relative to psoas major:

• Anterior: genitofemoral (on top or through)
• Medial: Obturator
• Lateral: all rest

Question 2

Iliohypogastric

Answer 2

Roots: L1

Lateral to psoas (superior) and posterior to kidney)

Sensory: posterolateral gluteal region and L1 dermatonal region of pubis

Motor: internal oblique and transverse abdominus

Question 3

Ilioinguinal

Answer 3

Roots: L1

Lateral to psoas (superior) and posterior to kidney), traverses anteriorly along with iliac crest

At ASIS:

• Pierces through TA and internal oblique fascia
• Runs thru superficial ring

Motor: internal oblique and TA

Sensory: upper medial thigh

Question 4

Genitofemoral

Answer 4

Roots: L1, 2

Lateral through psoas (anterior), posterior to ureter (inferior to kidney)

Divides into genital branch and femoral branch

Question 5

Genital Branch of Gentifemoral

Answer 5

Into inguinal canal

Motor: cremasteric muscle and skin on upper and anterior scrotum (men)

Sensory: overlapping sensation of ilioinguinal

Question 6

Femoral Branch of Genitofemoral

Answer 6

Under inguinal ligament to anterior medial thigh

Sensory only

Question 7

Lateral Femoral Cutaneous

Answer 7

Roots: L2, 3

Cutaneous

Lateral femoral cutaneous region

Deep to inguinal ligament

Question 8

Femoral

Answer 8

Roots: L2-4

Largest branch

Under inguinal ligament

Sensory: anterior central thigh, anterior medial shank via saphenous nerve

Motor: quads, iliacus, pectineus, sartorius

Question 9

Obturator

Answer 9

Roots: L2-4

Medial to psoas

Motor: obturator externus, pectineus (dual with femoral), adductors (longus, brevis, 1/2 magnus), gracilis

Sensory: medial upper thigh, hip joint

Question 10

Sacral Plexus

Answer 10

L4-S4

Anterior rami

Anterior/posterior divisions

Terminal nerves

Lie anterior to piriformis muscle (exit pelvis through greater sciatic foramen)

Question 11

External Rotators

Answer 11

Ventral division

Motor branch

N. to obturator internus and superior gemellus

N. to quadratus femoris and inferior gemellus

Piriformis muscle

Question 12

Pelvic Floor

Answer 12

Ventral division

Motor branch

Pudendal (levator ani, urogenital, anal triangle)

N. to levator ani, coccycgeus, ext. anal sphincter

Question 13

Motor Ventral Division

Answer 13

Tibial portion of sciatic

Pelvic splanchic (parasympathetic innervation)

Question 14

Sensory Ventral Division

Answer 14

Posterior femoral cutaneous

Anoccocygeal (cutaneous to skin and sacrococcygeal joint)

Question 15

Motor Dorsal Divisions

Answer 15

Superior gluteal nerve - glut med, glut min, TFL

Inferior gluteal nerve - glut max

Common fibular portion of sciatic nerve

Question 16

Sensory Dorsal Divisions

Answer 16

Common fibular portion of sciatic nerve

Posterior femoral cutaneous

Question 17

Clunial Nerves

Answer 17

Superior and middle

• Dorsal rami from vertebral column
• Superior portion of glut region

Inferior

• Ventral rami
• Lower portion of glut region