unit 4 second order

external oblique origin

Linea alba by a broad aponeurosis; some to iliac crest

external oblique insertion

External and inferior borders of the inferior 8 ribs

external oblique action

Unilateral action: Lateral flexion of vertebral column; rotation of vertebral column to opposite side

Bilateral action: Flexes vertebral column and compresses abdominal wall; used in forced exhalation

external oblique innervation

Spinal nerves T8-T12, L1

transversus abdominis origin

Linea alba and pubic crest

transversus abdominis insertion

Iliac crest, cartilages of inferior 6 ribs; lumbar fascia; inguinal ligament

transversus abdominis action

Bilateral action: Compresses abdominal wall; used in forced exhalation

transversus abdominis innervation

Spinal nerves T8-T12, L1

rectus abdominis origin

Superior surface of pubis near symphysis

rectus abdominis insertion

Xiphoid process of sternum; inferior surfaces of ribs 5-7

rectus abdominis action

Flexes vertebral column; compresses abdominal wall; used in forced exhalation

rectus abdominis innervation

Spinal nerves T7-T12

internal intercostals origin

Inferior border of superior rib

internal intercostals insertion

Superior border of inferior rib

internal intercostals action

Depresses ribs during forced exhalation; antagonistic to external intercostals

internal intercostals innervation

Thoracic spinal nerves

diaphragm origin

Inferior internal surface of ribs 7-12; xiphoid process of sternum and costal cartilages of inferior 6 ribs; lumbar vertebrae

diaphragm insertion

Central tendon

diaphragm action

Contraction causes flattening of diaphragm (moves inferiorly), and thus expansion of thoracic cavity; increases pressure in abdominopelvic cavity

diaphragm innervation

Phrenic nerves (C3-C5)