Transversus Abdominis muscle is a thin sheet-like muscle that lies deep to the internal oblique. It is the deepest of the lateral abdominal muscles. The muscle fibers run horizontally forward.
Origin of transversus abdominis:
Transversus abdominis originates from;
- Deep surface of lower six costal cartilages
- Lumbar fascia
- Anterior two thirds of the iliac crest
- Lateral third of inguinal ligament
The part of transversus abdominis, which originates from the costal cartilages, interdigitate with the attachment of diaphragm from the same place.
Insertion of transversus abdominis:
Transversus abdominis is inserted into:
- Xiphoid process
- Linea alba
- Symphysis pubis
The lowest tendinous fibers of transversus joint similar fibers from the internal oblique to form the conjoint tendon, which is fixed to the pubic crest and the pectineal line.
It should be appreciated that the posterior border of external oblique muscle is free, while the same borders of internal oblique and transversus abdominis are attached to the lumbar vertebrae through lumbar fascia.
Blood supply of transversus abdominis:
It receives its blood supply from;
- Lower posterior intercostal and subcostal arteries
- Superior and inferior epigastric arteries
- Superficial and deep circumflex arteries
- Posterior lumbar arteries
Nerve supply to transversus abdominis:
It is innervated by the branches of following nerves.
- Lower five intercostal nerves
- Subcostal nerve
- Iliohypogastric nerve
- Ilioinguinal nerve
The lower five intercostal and subcostal nerves represent the lower six thoracic spinal nerves while the iliohypogastric and ilioinguinal nerves represent the first lumbar spinal nerve.
Actions of transversus abdominis:
Main function of transversus abdominis is maintenance of abdominal tone. It also plays significant role in increasing the intra-abdominal pressure.