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Transversus abdominis muscle

The transversus abdominis (TrA) is the deepest of the three flat muscles of the anterolateral abdominal wall, lying beneath the internal oblique. It originates from the inner surfaces of the 7th–12th costal cartilages, thoracolumbar fascia, iliac crest, and lateral third of the inguinal ligament. Its fibers run transversely across the abdomen and insert into the linea alba, pubic crest, and pecten pubis via the conjoint tendon.

The transversus abdominis is often described as the “corset muscle” because its contraction significantly increases intra-abdominal pressure, stabilizes the lumbar spine, and provides dynamic support to the abdominal contents. Along with the diaphragm, multifidus, and pelvic floor muscles, it forms part of the core stabilizing unit.

Clinically, the TrA is vital in abdominal wall surgery, hernia repair, and physical rehabilitation. Weakness contributes to lumbar instability, abdominal hernias, and poor postural control. In surgery, it is a landmark in transversus abdominis plane (TAP) block, used for regional anesthesia of the abdominal wall.

Synonyms

  • Transverse abdominal muscle

  • Musculus transversus abdominis

  • Deep abdominal wall muscle

Function

  • Compresses and supports abdominal contents

  • Increases intra-abdominal pressure for defecation, micturition, and childbirth

  • Stabilizes lumbar spine and pelvis during movement

  • Assists in forced expiration and respiration

  • Provides structural support for abdominal wall integrity

Nerve Supply

  • Lower six thoracoabdominal nerves (T7–T11)

  • Subcostal nerve (T12)

  • Iliohypogastric and ilioinguinal nerves (L1)

Arterial Supply

  • Lower posterior intercostal arteries

  • Subcostal artery

  • Deep circumflex iliac artery

  • Inferior epigastric artery

Venous Drainage

  • Parallels arterial supply: intercostal, subcostal, and epigastric veins → azygos and external iliac venous systems

MRI Appearance

T1-weighted images:

  • Normal muscle shows intermediate signal intensity with visible fascicular pattern

  • Surrounding fat provides high contrast with the muscle sheath

T2-weighted images:

  • Muscle appears as intermediate-to-low signal intensity

  • Pathology such as edema or tears appear hyperintense

STIR:

  • Suppresses fat, highlighting muscle edema, inflammation, or hematomas as bright hyperintense signal

  • Useful in trauma or post-surgical evaluation

T1 Fat-Saturated (Pre-contrast):

  • Muscle shows intermediate signal standing out against suppressed fat planes of the abdominal wall

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Mild, homogeneous enhancement in normal muscle

  • Abnormal enhancement in cases of myositis, tumor, or infection

MRI Non-Contrast 3D Imaging:

  • Provides multiplanar assessment of TrA thickness and morphology

  • Useful for hernia mapping and surgical planning

CT Appearance

CT Pre-Contrast:

  • Muscle seen as a soft-tissue density layer, deepest among abdominal wall flat muscles

  • Helpful in detecting atrophy, hernia defects, or hematoma

CT Post-Contrast:

  • Shows homogeneous enhancement of muscle

  • Abnormal enhancement or thickening may indicate inflammation, neoplasia, or infection

  • 3D reconstructions useful in abdominal wall reconstruction planning

CT images

Transversus abdominis muscle ct axial image 1

CT images

Transversus abdominis muscle ct axial image

CT images

Transversus abdominis muscle ct coronal image

MRI image

Transversus abdominis muscle MRI axial image anatomy image -img-00000-00000