Trunk (thorax, abdomen, back)

Transversus Abdominis

Musculus transversus abdominis

Origin

Inguinal ligament, iliac crest, thoracolumbar fascia, and the inner surface of the lower six costal cartilages

Insertion

Linea alba and the pubic crest (via the conjoint tendon)

Function

Compresses the abdominal contents, raises intra-abdominal pressure, and stabilizes the lumbar spine

Innervation

Intercostal nerves T7-T12, iliohypogastric nerve and ilioinguinal nerve

Movement & chain

As the deepest abdominal muscle layer with predominantly horizontally running fibers, the primary muscle for local (segmental) stability of the lumbar spine, often the first trained in core stability exercises.

Palpation

Palpable beneath the internal oblique by gently pressing medial to the anterior superior iliac spine during coughing or bracing ("drawing in the abdomen").

Clinical

Inadequate activation of this muscle is associated with low back pain; it is often specifically trained in core stability rehabilitation.

Segmental innervation

T7-T12, L1 (iliohypogastric/ilioinguinal).

In clinical practice

The plane between this muscle and the internal oblique is the injection site for the TAP block (transversus abdominis plane block), a commonly used regional anesthesia technique for postoperative pain management after abdominal surgery.

Region in the model

Trunk (thorax, abdomen, back)