Transversus abdominis !
The transversus abdominis is the deepest abdominal muscle, wrapping the belly like a corset; it helps stiffen the spine before movement.
Official name: Transversus abdominis muscle
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What it is
The deepest abdominal muscle, wrapping around the belly like a corset from the thoracolumbar fascia to the front midline.
What it does
Raises pressure inside the abdomen and tightens the thoracolumbar fascia, helping stiffen the spine before you move.
Key facts
- Origin
- Inner surfaces of costal cartilages 7–12, thoracolumbar fascia, iliac crest, lateral third of inguinal ligament
- Insertion
- Linea alba via aponeurosis; pubic crest and pecten pubis via conjoint tendon
- Action
- Compresses abdominal contents; raises intra-abdominal pressure; tenses the thoracolumbar fascia
- Nerve
- Thoracoabdominal nerves (T7–T11), subcostal (T12), iliohypogastric and ilioinguinal (L1)
- Blood supply
- Deep circumflex iliac, inferior epigastric, lower posterior intercostal and lumbar arteries
Relations
- Superficial
- Internal oblique, with the lower thoracic, iliohypogastric and ilioinguinal nerves in the plane between them
- Deep
- Transversalis fascia, extraperitoneal fat and parietal peritoneum; the deep inguinal ring lies in the transversalis fascia, lateral to the inferior epigastric vessels
- Above
- Its upper fibres interlock with the costal fibres of the diaphragm on the inner costal cartilages
- Behind
- Its aponeurosis joins the thoracolumbar fascia around quadratus lumborum and the erector spinae; it forms the floor of the superior lumbar triangle
- Below
- Its lowest fibres arch over the inguinal canal with the internal oblique and join it in the conjoint tendon
How to find it
It cannot be felt. On ultrasound of the flank it is the deepest of the three layers, just above the peritoneum; drawing the navel gently toward the spine (abdominal hollowing) makes it thicken and slide visibly.
On imaging
Ultrasound shows the three flat muscles of the flank as dark layers separated by bright fascia; transversus abdominis is the deepest, just above the peritoneum. The TAP block is placed in the plane between it and the internal oblique. Ultrasound or CT shows a Spigelian hernia passing through its aponeurosis at the linea semilunaris, often hidden under an intact external oblique aponeurosis.
Common problems
- Delayed or weak activation is seen in some people with chronic low back pain.
How it is diagnosed
Exam; ultrasound can show its activation.
Treatment
- Core stability exercise programmes.
Clinical notes
- TAP block: under ultrasound, local anaesthetic placed between it and the internal oblique numbs the skin and muscle of the anterior abdominal wall after surgery
- Posterior component separation (transversus abdominis release) divides it to let the rectus abdominis move toward the midline in large hernia repairs
- Spigelian hernias come through the aponeurosis along the linea semilunaris, usually near the arcuate line, often hidden under an intact external oblique
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
Which way do the fibres of the transversus abdominis run, and where does it lie among the flat muscles?
Horizontally around the trunk; it is the deepest of the three flat abdominal muscles.
Between which layers is a TAP block given in relation to the transversus abdominis?
Between the transversus abdominis and the internal oblique, where the abdominal wall nerves run.
How does the transversus abdominis aponeurosis change at the arcuate line?
Above it the aponeurosis passes behind the rectus abdominis; below it, in front, leaving only transversalis fascia behind.
What nerves supply the transversus abdominis?
The thoracoabdominal nerves (T7–T11), the subcostal nerve (T12) and the iliohypogastric and ilioinguinal nerves (L1).
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- musculus transversus abdominis TA2 2375
- Official Spanish (DeCS)
- Músculo transverso del abdomen DeCS D000009
- English (TA2)
- Transversus abdominis muscle
- Also called
- transverse abdominal muscle
Related
- Thoracolumbar fascia
- Internal oblique
- Intercostal nerves
- Iliohypogastric and ilioinguinal nerves
- Hip bone
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Anterolateral Abdominal Wall Muscles.
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Representative model, for educational purposes only.
