Muscles of Posterior Abdominal Wall

Question 0

Iliacus

Answer 0

Origin: superior 2/3s of iliac fossa, ala of sacrum, and anterior sacro-iliac ligaments
Insertion: lesser trochanter of femur and shaft inferior to it and to psoas major tendon
Innervation: femoral nerve (L2-L4)
Action: flexes thigh and stabilizes hip joint, acts with psoas major

Question 1

Psoas Major and Minor

Answer 1

Origin: transverse processes of lumbar vertebrae; sides of bodies of T12-S1 vertebrae and intervening IV discs
Insertion: by a strong tendon to the lesser trochanter of the femur
Innervation: lumbar plexus vis anterior branches of nerves L2-L4
Action: Acting inferiorly with iliacus flexes thigh; acting superiorly flexes vertebral column laterally to balance the trunk; when sitting, acts inferiorly with iliacus to flex trunk

Question 2

Quadratus Lumborum

Answer 2

Origin: medial 1/2 of inferior border of 12th rib and tips of lumbar transverse processes
Insertion: iliolumbar ligament and internal lip of iliac crest
Innervation: anterior branches of T12 and L1-L4 nerves
Action: extends and laterally flexes vertebral column; fixes 12th rib during inspiration