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Attachments, innervation and functions of the transversus abdominis muscle.
Hello again! It’s Matt from Kenhub, and in this tutorial, we will discuss the transversus abdominis. The lateral abdominal muscles are part of the tension system of the abdominal wall musculature. Together with the anterior abdominal muscles, they form the musculature of the anterior body wall. The lateral abdominal muscles are made up of the abdominal external oblique muscle, abdominal internal oblique muscle, and the transversus abdominis muscle which is the focus of this short video tutorial.
The transversus abdominis muscle has 4 points of origin running from the inner surface of the 7th to 12th costal cartilages, the thoracolumbar fascia, the iliac crest horizontally, and the inguinal ligament. It has its insertion on the linea alba. The innervation of the transverse abdominis is supplied by the 7th to 12th intercostal nerves as well as the branches of the lumbar plexus namely the iliohypogastric nerve and the ilioinguinal nerve.
The aponeurosis of the lateral abdominal muscles build the rectus sheath, a tendinous envelope for the rectus abdominis muscle. It is divided into an anterior and posterior layer which interdigitate in the median line called the linea alba. Above the arcuate line, about 4-5 cm caudal of the umbilicus, the anterior layer of the rectus sheath consists of the aponeurosis of the internal and external oblique and the posterior layer is made up of the aponeurosis of the internal oblique and transverse abdominis. Below the arcuate line, the anterior layer of the rectus sheath is built by the aponeurosis of all 3 lateral abdominal muscles whereas the posterior layer is only covered by the transverse fascia and the peritoneum.
The abdominal muscles are responsible for the tension of the anterior body wall. In collaboration with the back musculature, they stabilize the vertebral column and move the trunk. Through abdominal press, they increase the intra-abdominal pressure and, thereby, support emptying processes such as defecation and urination and also support exhalation. A unilateral contraction of the transversus abdominis leads to an ipsilateral rotation along with the internal oblique muscle.
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