Simplified Thoracic Cage Muscles

External intercostals — Origin

Ribs

External intercostals — Insertion

Inferior adjacent ribs

External intercostals — Action

Elevation of ribs (inspiration)

External intercostals — Innervation

Intercostal nerves

Internal intercostals — Origin

Ribs

Internal intercostals — Insertion

Superior adjacent ribs

Internal intercostals — Action

Depression of ribs (expiration)

Internal intercostals — Innervation

Intercostal nerves

Innermost intercostals — Origin

Ribs

Innermost intercostals — Insertion

Superior adjacent ribs

Innermost intercostals — Action

Depression of ribs (expiration)

Innermost intercostals — Innervation

Intercostal nerves

Subcostals — Origin

Ribs

Subcostals — Insertion

Superior non-adjacent ribs

Subcostals — Action

Depression of ribs (expiration)

Subcostals — Innervation

Intercostal nerves

Transversus thoracis — Origin

Sternum

Transversus thoracis — Insertion

Ribs (via costal cartilages → chart shows cervical vertebrae but likely ribs)

Transversus thoracis — Action

Depression of ribs (expiration)

Transversus thoracis — Innervation

Intercostal nerves

Diaphragm — Origin

Ribs

Diaphragm — Origin

Vertebrae

Diaphragm — Insertion

Central tendon

Diaphragm — Action

Inspiration

Diaphragm — Innervation

Phrenic nerve

Rectus abdominis — Origin

Pubis

Rectus abdominis — Insertion

Costal cartilages

Rectus abdominis — Action

Flexion of spine

External oblique — Origin

Ribs

External oblique — Insertion

Linea alba

External oblique — Action

Flexion of spine

External oblique — Action

Rotation of spine

External oblique — Action

Lateral flexion of spine

External oblique — Innervation

Anterior rami

Internal oblique — Origin

Iliac crest

Internal oblique — Insertion

Linea alba

Internal oblique — Action

Flexion of spine

Internal oblique — Action

Rotation of spine

Internal oblique — Action

Lateral flexion of spine

Internal oblique — Innervation

Anterior rami

Transversus abdominis — Origin

Ribs

Transversus abdominis — Origin

Iliac crest

Transversus abdominis — Insertion

Linea alba

Transversus abdominis — Action

Increase abdominal pressure

Transversus abdominis — Innervation

Anterior rami

Quadratus lumborum — Origin

Vertebrae

Quadratus lumborum — Origin

Ribs

Quadratus lumborum — Insertion

Iliac crest

Quadratus lumborum — Action

Extension of spine

Quadratus lumborum — Action

Lateral flexion of spine

Psoas minor — Origin

Vertebrae

Psoas minor — Insertion

Pubis

Psoas minor — Action

Flexion of spine (minimal)

Psoas major — Origin

Vertebrae

Psoas major — Insertion

Lesser trochanter (femur)

Psoas major — Action

Hip flexion

Psoas major — Innervation

Femoral nerve

Iliacus — Origin

Ilium

Iliacus — Insertion

Lesser trochanter (femur)

Iliacus — Action

Hip flexion

Iliacus — Innervation

Femoral nerve