Spine and Thorax Abdominal Muscles

Rectus Abdominis Action

Flex the vertebral column
Tilt pelvis posteriorly

Rectus Abdominis Origin

Pubic crest, pubic symphysis

Rectus Abdominis Insertion

Cartilage of 5th, 6th and 7th ribs and xiphoid process

Rectus Abdominis Innervation

T5-T12 and ventral rami

External Oblique Action

Unilaterally: laterally flex vertebral column to the same side, rotate vertebral column to opposite side
Bilaterally: Flex the vertebral column and compress abdominal contents

External Oblique Origin

External surfaces of 5th-12th rib

External Oblique Insertion

Anterior part of the iliac crest, rectus sheath to linea alba

External Oblique Innervation

T5-T12

Internal Oblique Action

Unilaterally: Laterally flex vertebral column and rotate trunk to same side
Bilaterally: Flex the vertebral column and compress abdominal content

Internal Oblique Origin

Lateral inguinal ligament, iliac crest, and thoracolumbar fascia

Internal Oblique Insertion

Internal surface of lower 3 ribs, rectus sheath to linea alba

Internal Oblique Innervation

T7, 8, T9-T12, L1, iliohypogastric and illioinguinal ventral rami

Transverse Abdominis Action

Compresses abdominal contents

Transverse Abdominis Origin

Lateral inguinal ligament, iliac crest, thoracolumbar fascia, and internal surface of lower six ribs

Transverse Abdominis Insertion

Rectus sheath to linea alba

Transverse Abdominis Innervation

T7-12, L1, iliohypogastric and ilioinguinal, ventral divisions