Transverse abdominal muscle

Transverse abdominal muscle
Muscles of the trunk.
The Transversus abdominis, Rectus abdominis, and Pyramidalis.
Details
Origin	Iliac crest, inguinal ligament, thoracolumbar fascia, and costal cartilages 7-12
Insertion	Xiphoid process, linea alba, pubic crest and pecten pubis via conjoint tendon
Artery	subcostal arteries.
Nerve	Thoracoabdominal nn. (T6-T11), Subcostal n. (T12), iliohypogastric nerve (L1), and ilioinguinal nerve (L1).
Actions	Compresses abdominal contents
Identifiers
Latin	Musculus transversus abdominis
TA98	A04.5.01.019
TA2	2375
FMA	15570
Anatomical terms of muscle

The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall which is deep to (layered below) the internal oblique muscle. It is thought by most fitness instructors to be a significant component of the core.

Structure

The transverse abdominal, so called for the direction of its fibers, is the innermost of the flat muscles of the abdomen. It is positioned immediately inside of the internal oblique muscle.

The transverse abdominal arises as fleshy fibers, from the lateral third of the inguinal ligament, from the anterior three-fourths of the inner lip of the iliac crest, from the inner surfaces of the cartilages of the lower six ribs, interdigitating with the diaphragm, and from the thoracolumbar fascia. It ends anteriorly in a broad aponeurosis (the Spigelian fascia), the lower fibers of which curve inferomedially (medially and downward), and are inserted, together with those of the internal oblique muscle, into the crest of the pubis and pectineal line, forming the inguinal conjoint tendon also called the aponeurotic falx. In layman's terms, the muscle ends in the middle line of a person's abdomen.^{[1]: 248–250}

Throughout the rest of its extent the aponeurosis passes horizontally to the middle line, and is inserted into the linea alba; its upper three-fourths lie behind the rectus muscle and blend with the posterior lamella of the aponeurosis of the internal oblique; its lower fourth is in front of the rectus abdominis.

Function

The transverse abdominal helps to compress the ribs and viscera, providing thoracic and pelvic stability. This is explained further here. The transverse abdominal also helps a pregnant woman to deliver her child.

Without a stable spine, one aided by proper contraction of the TVA, the nervous system fails to recruit the muscles in the extremities efficiently, and functional movements cannot be properly performed.^[2] The transverse abdominal and the segmental stabilizers (e.g. the multifidi) of the spine have evolved to work in tandem.

While it is true that the TVA is vital to back and core health, the muscle also has the effect of pulling in what would otherwise be a protruding abdomen (hence its nickname, the “corset muscle”). Training the rectus abdominis muscles alone will not and can not give one a "flat" belly; this effect is achieved only through training the TVA.^[3] Thus to the extent that traditional abdominal exercises (e.g. crunches) or more advanced abdominal exercises tend to "flatten" the belly, this is owed to the tangential training of the TVA inherent in such exercises. Recently the transverse abdominal has become the subject of debate between biokineticists, kinesiologists, strength trainers, and physical therapists. The two positions on the muscle are (1) that the muscle is effective and capable of bracing the human core during extremely heavy lifts and (2) that it is not. Specifically, one recent systematic review has found that the baseline dysfunction of TVA cannot predict the clinical outcomes of low back pain.^[4] Similarly, another systematic review has revealed that the changes in TVA function or morphology after different nonsurgical treatments are unrelated to the improvement of pain intensity or low back pain related-disability.^[5] These findings have challenged the traditional emphasis of using TVA-targeted intervention to treat low back pain.

Additional images

• 
  Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the lumbodorsal fascia.
• 
  Posterior surface of sternum and costal cartilages, showing Transversus thoracis.
• 
  The interfoveolar ligament, seen from in front.
• 
  Diagram of sheath of Rectus.
• 
  Diagram of a transverse section through the anterior abdomina wall, below the linea semicircularis.
• 
  The abdominal inguinal ring.
• 
  The abdominal aorta and its branches.

References

This article incorporates text in the public domain from page 414 of the 20th edition of Gray's Anatomy (1918)

External links

• Anatomy figure: 35:07-04 at Human Anatomy Online, SUNY Downstate Medical Center - "Incision and reflection of the internal abdominal oblique muscle."
• Anatomy photo:35:17-0100 at the SUNY Downstate Medical Center - "Anterior Abdominal Wall: The Transversus Abdominis Muscle"
• Anatomy figure: 40:07-06 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles and nerves of the posterior abdominal wall."
• Anatomy image:7183 at the SUNY Downstate Medical Center
• Anatomy image:7194 at the SUNY Downstate Medical Center
• Anatomy image:7209 at the SUNY Downstate Medical Center
• Anatomy image:7311 at the SUNY Downstate Medical Center