Internal Abdominal Oblique Muscle

Origin

The internal abdominal oblique muscle originates from the:

- thoracolumbar fascia;

- anterior two thirds of the iliac crest;

- lateral two thirds of the inguinal ligament.

Insertion

The fibers of the internal abdominal oblique muscle travel in anterior, medial and superior directions around the abdomen and insert onto the:

- inferior margins and costal ends of the tenth to twelfth ribs and their adjacent costal cartilages;

- linea alba, via its broad aponeurosis;

- pecten pubis, via its inguinal falx.

Key Features & Anatomical Relations

The internal abdominal oblique muscle is one of the muscles of the abdomen. It is a broad, flat skeletal muscle.

Adjacent to the midclavicular line, the muscle belly gives rise to a broad aponeurosis of internal abdominal oblique, which contributes to the formation of the anterior and posterior layers of the rectus sheath.

The internal abdominal oblique muscle is located:

- superficial to the transversus abdominis muscle;

- deep to the external abdominal oblique muscle;

- lateral to the rectus abdominis muscle.

The internal abdominal oblique contributes to the formation of the:

- anterolateral abdominal wall;

- inguinal canal;

- lumbar triangle (triangle of Petit), where the internal abdominal oblique muscle forms its floor.

Actions

The internal abdominal oblique muscle is involved in multiple actions:

- during unilateral contraction, it laterally flexes the trunk to the same side;

- during unilateral contraction, it rotates the trunk to the same side;

- during bilateral contraction, it flexes the trunk;

- it compresses and provides structural support to adjacent abdominal structures;

- it depresses the ribs at their costovertebral joints during forced expiration (Sinnatamby, 2011).

List of Clinical Correlates

- Inguinal hernias

- Spigelian hernia (Kasirajan, Lopez and Lopez, 1997)

References

Kasirajan, K., Lopez, J. and Lopez, R. (1997) 'Laparoscopic technique in the management of Spigelian hernia', J Laparoendosc Adv Surg Tech A, 7(6), pp. 385-8.

Sinnatamby, C. S. (2011) Last's Anatomy: Regional and Applied. ClinicalKey 2012: Churchill Livingstone/Elsevier.

Actions

The internal abdominal oblique muscle is involved in multiple actions:

- during unilateral contraction, it laterally flexes the trunk to the same side;

- during unilateral contraction, it rotates the trunk to the same side;

- during bilateral contraction, it flexes the trunk;

- it compresses and provides structural support to adjacent abdominal structures;

- it depresses the ribs at their costovertebral joints during forced expiration (Sinnatamby, 2011).