quadratus lumborum muscle

Introduction

Flat muscle of the posterior abdominal wall.

Origin

• internal lip of iliac crest
• iliolumbar ligament
• transverse processes of the lower lumbar vertebrae

Insertion

• 12th rib
• transverse processes of the upper lumbar vertebrae

Action

• extends & laterally flexes vertebral column
• abducts the trunk
• fixes 12th rib during inspiration

Innervation

• ventral primary rami of T12
• ventral primary rami of L1-L4

More general terms

• skeletal muscle (voluntary muscle)