Muscles of the Anterior Abdomen

External abdominal oblique m. (133) Internal abdominal oblique m. (134) Transversus abdominis m. Rectus abdominis m. (135) Pyramidalis m. Cremaster m. (136) Quadratus lumborum m. (137)

Generalized motions of the abdominal muscles In general, muscle have two attachment sites: Origin Insertion

For abdominal muscles, one set of attachment sites is often on the pelvis, while the other is on the trunk For some of the abdominal muscles, either the attachment on the trunk OR the attachment on the pelvis can be the fixed site, while the other attachment site moves. For that reason, we will talk about distal and proximal attachments for some of these muscles, rather than origin and insertion

Flexion (anterior) or extension (posterior) of the trunk on the pelvis Anterior or posterior tilt of the pelvis Lateral flexion of the trunk on the pelvis Lifting up of one side of the pelvis

Rotation of the trunk on the pelvis Rotation of the pelvis Ipsilateral rotation – when a muscle contracts, an anterior point on the moving region rotates toward the side of the muscle Contralateral rotation – The anterior surface of the body region rotates away from the contracting muscle

Iliac Crest Three lips Each lip is an attachment site for one of the three lateral abdominal muscles

Ext. Abd. Oblique m. Proximal and distal attachment sites T7-T12 Stabilizes trunk Compresses abdominal viscera Bilateral and unilateral actions Trunk movements Pelvic movements

Int. Abd. Obllique m. Proximal and distal attachment sites T7-T12, L1 Stabilizes trunk Compresses abdominal viscera Bilateral and unilateral actions Trunk movements Pelvic movements

Transversus Abd. m. Origin and insertion T7-T12, L1 Stabilizes trunk Compresses abdominal viscera

Rectus Abd. M. Proximal and distal attachments 3 Tendinous insertions Muscle can contract in segments T5-T12 Stabilizes Trunk Compresses abdominal viscera Bilateral actions Trunk movement Pelvic movement

Quad. Lumb. M. Proximal and distal attachments T12, L1-L3 Unilateral and bilateral actions Pelvis stable Trunk stable

Stabilizing actions Limit movement of the trunk Which muscles do this and which movements do they limit? Why is this important?

Compress Viscera Increases abdominal pressure What is this needed for?

Pyramidalis muscle

Cremaster muscle