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Transverse abdominal muscle

The transverse abdominal muscle (transversus abdominis) is the deepest layer of the anterolateral abdominal wall muscles. It forms a broad muscular sheet that encircles the abdomen and plays a major role in abdominal wall tension, visceral support, and core stability.

It is an important anatomical structure in abdominal wall integrity, hernia formation, postoperative assessment, and imaging of the abdominal wall.

Synonyms

  • Transversus abdominis muscle

  • Transverse abdominalis muscle

Location

  • Situated in the deepest muscular layer of the lateral abdominal wall

  • Deep to the internal oblique muscle

  • Superficial to the transversalis fascia and peritoneum

  • Extends from the costal margin superiorly to the pelvis inferiorly

  • Forms part of the anterior abdominal wall and flank regions

Anatomical components

  • Flat, thin muscular sheet

  • Muscle fibers oriented horizontally (transversely)

  • Aponeurotic portion:

    • Contributes to the posterior and anterior rectus sheath

  • Lower fibers:

    • Contribute to the inguinal region and conjoint tendon

Relations

Superficially:

  • Internal oblique muscle

  • External oblique muscle (more superficial layer)

Deep:

  • Transversalis fascia

  • Extraperitoneal fat

  • Parietal peritoneum

Medially:

  • Rectus sheath and linea alba

Laterally:

  • Lateral abdominal wall fascia

Superiorly:

  • Lower ribs and costal margin

Inferiorly:

  • Iliac crest

  • Inguinal region

Structures related to the muscle

  • Thoracolumbar nerves (T7–L1) coursing between internal oblique and transversus abdominis

  • Deep circumflex iliac vessels

  • Inguinal canal (inferomedial fibers)

Function

  • Abdominal wall tension: Compresses abdominal contents

  • Core stabilization: Provides deep trunk stability

  • Respiratory assistance: Aids forced expiration

  • Postural control: Essential for spinal and pelvic stability

X-ray appearance

Plain abdominal radiographs:

  • Transverse abdominal muscle: Not directly visualized

  • Assessment: Inferred from abdominal wall contour

  • Bony landmarks: Ribs, iliac crests, and spine used for orientation

CT appearance (pre-contrast)

Non-contrast CT:

  • Muscle layer: Thin, symmetric soft-tissue density layer deep to internal oblique

  • Fiber plane: Horizontal orientation of muscle fibers

  • Fascial planes: Clear separation from transversalis fascia and peritoneum

  • Abdominal wall symmetry: Bilateral uniform thickness

MRI appearance

T1-weighted images:

  • Normal muscle: Intermediate signal intensity

  • Fascial planes: Low-signal thin lines separating muscle layers

  • Subcutaneous fat: High signal superficial to muscle

T2-weighted images:

  • Normal muscle: Low-to-intermediate signal

  • Internal architecture: Homogeneous appearance

  • Perimuscular fat: Higher signal than muscle

STIR:

  • Normal muscle: Low-to-intermediate signal

  • Edema-sensitive sequence: Muscle normally shows no hyperintensity

  • Fascial planes: Well delineated

MRI image

Transverse abdominal muscle mri anatomy Location and Imaging Appearance -img-00000-00000

CT image

Transverse abdominal muscle CT anatomy Location and Imaging Appearance -img-00000-00000

CT image

Transverse abdominal muscle CT anatomy Location and Imaging Appearance -img-00000-00000_00001