Anatomy and Function of the Posterior Abdominal Muscle

Hello everyone, In my previous post, I wrote on Anatomy and Function of the Anterior Abdominal Muscle, where I explained the five muscles which are the pyramidalis muscle, Rectus Abdominis muscle (known as the Six-pack muscle), External Abdominal Oblique Muscle, Internal Abdominal Oblique Muscle, and the Transversus Abdominis Muscle. I will be writing today on the anatomy and functions of the Posterior Abdominal Wall.

The posterior abdominal wall is the back side of the posterior muscle region of the abdominal cavity, which is located between the thoracic cavity and the pelvis. The Posterior abdominal wall is made up of four muscles which are the Psoas Major Muscle, the Iliacus Muscle, Quadratus Lumborum Muscle, and Psoas minor muscle.

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Iliopsoas group

The Iliopsoas Muscle group is a group that consists of two muscles, the iliacus muscle, and the psoas muscle. The muscle group is located in the anterior (front) of the hip and lower back. The Psoas Major Muscle originates from the vertebral body T12 through L4, and the associated intravertebral disc, it also originates from the transverse processes L1 to L5. The musculotendinous junction of the Psoas major muscle blends with the musculotendinous junction of the Iliacus muscle where it forms a tendon known as the Iliopsoas tendon or conjoined tendon that exits from the pelvic cavity, attaching at the lesser trochanter located at the femur. It is responsible for the flexion of the hip in external rotation and the ipsilateral lateral flexion of the trunk. It is innervated by the anterior rami of the spinal nerve L1 to L3 and blood is supplied to the muscle through the lumber branch of the Iliolumbar artery (the Iliolumbar arteries are small branches of the posterior division of the internal iliac artery).

The Iliacus muscle which is part of the Iliopsoas group has its origin at the iliac fossa. It inserts through the musculotendinous junction just like the Psoas major muscle where they both form a tendon Iliopsoas tendon which then inserts into the lesser trochanter of the femur. Similar to the Psoas major muscle, it allows for hip flexion, allowing the external rotation of the hip, and the flexion of the trunk. It is innervated via the femoral nerve L1 through L3, and blood is supplied to the muscle through the femoral artery, the iliolumbar artery, the deep circumflex iliac artery, and the Obturator artery.

Clinical Relevance of the Ilopsoas Group

People who sit for a long time without being active suffer from sitting disease which causes hip flexor tightness, hip pain, femoral nerve entrapment, excessive anterior pelvic tilt, and weakness of the rectus abdominus muscle. Another clinical condition associated with the iliopsoas group muscle is the Psoas abcess where there is a painful collection of pus in an iliopsoas muscle. It is usually treated with antibotics and the drainange of the abcess.

Quadratus Lumborum Muscle

The quadratus lumborum muscle is a deep muscle located in the lower back. This muscles descend down from the arcuate ligament, and it originates from the iliac crest and the iliolumber ligament. The muscle fibers run vertically upwards inserting on the inferior border of the Rib 12, and the transverse processes of vertebrae L1 through L4. Bilateral contraction of the Quadratus Lumborum Muscle allows for rib 12 fixation during inspiration, and trunk extension (Extension of the lumbar spine), Stabilizing the lower back, and unileteral contraction of the Quadratus Lumborum Muscle allows for the ipsilateral lateral flexion. The Quadratus Lumborum Muscle is innervated by the subcostal nerve T12, and the Anterior Remi of L1 through L4. Blood is supplied to the muscle through the Lumbar artery, Median Sacral artery, Iliolumbar artery, and the Subcostal artery. If the Quadratus Lumborum Muscle is strained, it can lead to certain clinical condition such as low back pain as it weakens the intrinsic back muscles, stiffening of the muscle and pain, Unequal leg lenghts can also cause the Quadratus Lumborum Muscle to be overused as well as sitting for a prolonged period of time.

Psoas Minor Muscle

The psoas minor is thin muscle located in the front of the lumbar spine, beneath the medial arcuate ligament. it is anterior to the Psoas major which is bigger than the Psoas minor. The Psoas minor originates from the T12 and L1 vertebral bodies. The psoas minor muscle is a flexor of the hip and trunk helping in side bending and rotation of the lumbar spine. It is innervated by the anterior ramus of L1. It doesn't really contribute to trunk flexion much and is likely to perform proprioceptive function, and it is missing in a lot of people. People who have Agenesis tend not to have the muscle and about 33% of the population suffer from this condition. Blood is supplied to the Psoas Minor Muscle through the lumber artery.

Conclusion

In conclusion, let me explains that the posterior and the anterior abdominal walls a the abdominal muscles that are responsible for flexion and protection of our abdominal cavity, and the movement of different parts of the body. The posterior abdominal wall is found at the back while the anterior muscles are found in the frontsides of the abdomen.

Reference

Hi, I am Tobi a writer, speaker, relationship blogger, and lover of good music. I love making friends and learning from people. Want to hear me speak on relationships and general life issues, you can find my podcast channel Here and I also have a youtube channel where you can listen and watch any episode for free, do not forget to subscribe and share with friends. I sincerely appreciate every love I get from members of the community and do well to keep them coming.