Abdominal wall muscles

Authors
Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Muscles of the Abdomen1
Note

Brad Jones2 separated the abdominal wall into 2 sections:

  • Anterolateral
    • External oblique
    • Internal oblique
    • Transversus abdominis
    • Rectus abdominis
    • Pyramidalis
  • Posterior
    • Psoas major
    • Iliacus
    • Quadratus lumborum (QL)
    • Psoas minor2
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Muscle Origin Insertion Innervation Action
External oblique
Iliacus Iliac Fossa Lesser Trochanter Femoral n.
L2 - L3		 Hip: Flexion, ER
L/S (UNIL contraction on fixed femur): I/L spine sidebend
L/S (BIL contraction): Raises trunk from supine position
Internal oblique
Psoas Major T12-L4 and associated IV discs
L1-L5 TP		 Lesser Trochanter Lumbar Plexus Direct Br.
L1 - L3		 Hip: Flexion, ER
L/S (unilateral contraction with femur fixed): I/L spine sidebend
L/S (bilateral contraction): Raises trunk from supine position
Psoas Minor T12, L1 vertebrae (lateral aspect) and IVD Pectineal Line
Iliopubic ramus
Iliac fascia
Inguinal ligament		 Spinal nn.
L1 - L3		 Trunk: Weak flexion
Pyramidalis T12 Tenses linea alba
Quadratus lumborum
Rectus abdominis Trunk: Flexion
Abdomen: Compression
Pelvic: stabilization
Transversus abdominis

Anterolateral abdominal wall

The 5 paired muscles of the anterolateral abdominal wall can be divided into 2 groups2:

Anterior vertical muscles

  • Rectus abdominis2
  • Pyramidalis2

Lateral flat muscles

  • Transverse abdominis
  • Internal oblique
  • External oblique

Hollowing

All of these muscles are important for flexion and “hollowing”2. Each part of the abdominal wall draws in a different part of the body towards the midline of the (linea alba). The external obliques draw in the ribcage infero-medially. The internal obliques draw the ilium superior medially. the transverse abdominis draws the sides of the body medially. The rectus abdominis pulls the ribcage inferiorly and pelvis superiorly.

Trunk Flexion

2 levers:

  1. Pubic symphysis to the sacral promontory
  2. Xiphoid to thoracic spine

References

1.
Betts JG, Blaker W. Anatomy and Physiology. 2nd ed. OpenStax; 2022. https://openstax.org/details/books/anatomy-and-physiology-2e/?Book%20details
2.
Jones B. B Project Foundations. b Project; 2025.

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