Rectus sheath

Template:Infobox Anatomy The Rectus sheath is formed by the aponeuroses of the Obliqui and Transversus. It contains the Rectus abdominis and Pyramidalis muscles.

It can be divided into anterior and posterior laminae.

The arrangement of the layers has important variations at different locations in the body.

Below the costal margin

For context, above the sheath are the following three layers:

1. superficial fascia
2. Camper's fascia
3. Scarpa's fascia

Within the sheath, the layers vary:

Region	Illustration	Description
Above the umbilicus		At the lateral margin of the Rectus, the aponeurosis of the Obliquus internus divides into two lamellae: one of which passes in front of the Rectus, blending with the aponeurosis of the Obliquus externus. the other, behind it, blending with the aponeurosis of the Transversus, and these, joining again at the medial border of the Rectus, are inserted into the linea alba.
Below the arcuate line		Below this level, the aponeuroses of all three muscles (including the internus) pass in front of the Rectus.

Below the sheath are the following three layers:

1. transversalis fascia
2. extraperitoneal fat
3. parietal peritoneum

The Rectus, in the situation where its sheath is deficient below, is separated from the peritoneum only by the transversalis fascia, in contrast to the upper layers, where part of the internal oblique also runs beneath the rectus. Because of the thinner layers below, this region is more susceptible to herniation.

Above the costal margin

Since the tendons of the Obliquus internus and Transversus only reach as high as the costal margin, it follows that above this level the sheath of the Rectus is deficient behind, the muscle resting directly on the cartilages of the ribs, and being covered merely by the tendon of the Obliquus externus.

Additional images

• 
  The Cremaster
• 
  The interfoveolar ligament, seen from in front.

External links

• Template:SUNYAnatomyFigs - "Incisions and the contents of the rectus sheath."
• Template:SUNYAnatomyLabs - "Anterior Abdominal Wall: The Rectus Abdominis Muscle"
• Template:SUNYAnatomyImage - anterior layer
• Template:SUNYAnatomyImage - posterior layer above arcuate line
• Template:SUNYAnatomyImage - posterior layer above arcuate line
• Template:GPnotebook
• Template:NormanAnatomy
• Template:UMichAtlas - "The Rectus Sheath, Anterior View & Transverse Section"
• Template:MUNAnatomy