Transversus Abdominis

The transversus abdominis is a muscle of the anterior abdominal wall. It is the deepest of the flat abdominal wall muscles.

• Attachments: Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. It inserts onto the conjoint tendon, xiphoid process, linea alba and the pubic crest.
• Actions: Compression of abdominal contents.
• Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.
• Blood supply: Lower posterior intercostal and subcostal arteries, superior and inferior epigastric arteries, superficial and deep circumflex arteries, posterior lumbar arteries.

By OpenStax [CC BY 4.0], via Wikimedia Commons

Fig 1
The muscles of the anterolateral abdominal wall. Note how the flat muscles form aponeuroses medially.