Posterior Abdominal Wall Muscles

Question 1

Psoas Major

Answer 1

O: TPs of Lumbar Vertebrae; sides of bodies of T12-L5 vertebrae and intervening IV discs
I: By a strong tendon to lesser trochanter of Femur
N: APR of Lumbar Nerves L1-3
A: acting inferiorly with iliac, it flexes thigh; acting superiorly it flexes vertebral column laterally; it is used to balance the trunk; when sitting it acts inferiorly with iliac to flex trunk

Question 2

Iliacus

Answer 2

O: superior 2/3 of iliac fossa, ala of sacrum, and anterior sacroiliac ligaments
I: Lesser Trochanter of Femur and Shaft inferior to it, and to Psoas Major tendon
N: Femoral Nerve (L2-L4)
A: flexes thigh and stabilizes hip joint; acts with psoas major

Question 3

Quadratus Lumborum

Answer 3

O: Medial half of Inferior border of 12th ribs and tips of Lumbar TPs
I: Iliolumbar Ligaments and Internal Lip of Iliac Crest
N: Anterior branches of T12 and L1-L4 nerves
A: extends and laterally flexes vertebral column; fixes 12th rib during inspiration