Posterior Abdominal Wall Muscles

Question 1

Psoas Major

Answer 1

O: transverse processes of lumbar vertebrae; sides of bodies T 12-L5 and intervening discs
I: lesser trochanter of femur
A: acting superiorly with ilicuas- flexes hip; acting inferiorly- used to balance trunk in sitting position; w/ iliacus- flexes hip
I: lumbar plexus and anterior branches L1-L3

Question 2

Iliacus

Answer 2

O: superior two thirds of iliac fossa, ala of sacrum and anterior sacroiliac ligaments
I: lesser trochanter of femur and shaft of inferior to it, and to psoas major tendon
A: flexes hip and stabilizes hip joint; acts with psoas major
I: femoral nerve (L2-L4)

Question 3

Quadratus lumborum

Answer 3

O: medial half of inferior border of the 12th rib and tips of lumbar transverse processes
I: iliolumbar ligament and internal lip of iliac crest
A: extends and laterally flexes vertebral column; fixes 12th rib during inspiration
I: anterior branch of T12 and L1-L4nerve

Question 4

Respiratory diaphragm

Answer 4

O: xiphoid process, lower six costal cartilages, L1-L3 vertebrae
I: converge into central tendon
A: draws central tendon down and forward during inspiration
I: phrenic nerve (C3-C5)