Oblique muscle

Oblique Muscle

The oblique muscles, shown in a diagram from Gray's Anatomy.

The oblique muscle is a broad, thin, irregularly quadrilateral muscle group that forms the lateral wall of the abdomen. It is divided into three layers: the external oblique, the internal oblique, and the transversus abdominis.

Structure

External Oblique

The external oblique is the largest and most superficial of the three oblique muscles. It originates from the lower eight ribs and inserts into the iliac crest, linea alba, and the pubic tubercle.

The external oblique muscle.

Internal Oblique

The internal oblique lies just deep to the external oblique. It originates from the thoracolumbar fascia, the anterior two-thirds of the iliac crest, and the lateral half of the inguinal ligament. It inserts into the inferior borders of the 10th through 12th ribs, the linea alba, and the pecten pubis via the conjoint tendon.

The internal oblique muscle.

Transversus Abdominis

The transversus abdominis is the deepest of the three oblique muscles. It originates from the internal surfaces of the 7th to 12th costal cartilages, thoracolumbar fascia, iliac crest, and the lateral third of the inguinal ligament. It inserts into the linea alba with the aponeurosis of the internal oblique, the pubic crest, and the pecten pubis via the conjoint tendon.

The transversus abdominis muscle.

Function

The oblique muscles function to flex and rotate the trunk, as well as to increase intra-abdominal pressure. They also assist in forced respiration, aid in raising intra-abdominal pressure and, with the pelvic floor, act as a supportive shelf for the visceral contents while lifting or straining.

See also

• Abdominal exercise
• Rectus abdominis muscle
• Pyramidalis muscle