Anterior layer of rectus sheath

The anterior layer of rectus sheath is is the front fibrous covering of the rectus abdominis muscle. The composition of the anterior layer differs above and below the arcuate line.

Above the Arcuate Line

Above the arcuate line, the anterior layer is formed by:

• The aponeurosis of the external oblique muscle

• The anterior lamina of the internal oblique aponeurosis

At this level; above the arcuate line, the internal oblique aponeurosis splits into anterior and posterior laminae to enclose the rectus abdominis muscle.

Below the Arcuate Line

Below the arcuate line, all three aponeuroses pass anterior to the rectus abdominis muscle. Therefore, the anterior layer is formed by:

• External oblique aponeurosis

• Internal oblique aponeurosis

• Transversus abdominis aponeurosis

As a result, the anterior wall of the sheath becomes thicker inferiorly, while the posterior wall is absent.

Functions

The anterior layer of the rectus sheath protects and encloses the rectus abdominis muscle, and helps maintain abdominal wall strength.