What is the rectus sheath and what is its function?

The rectus sheath is an aponeurotic sheath that encloses the rectus abdominis and pyramidalis muscles. It improves muscle efficiency by preventing bowing during contraction and reinforces the structural strength of the anterior abdominal wall.

How does the formation of the rectus sheath change at different levels of the abdomen?

Above the costal margin, the sheath has only an anterior wall from the external oblique aponeurosis. Between the costal margin and arcuate line, the anterior wall includes external and internal oblique, while the posterior wall includes transversus abdominis and internal oblique. Below the arcuate line, the anterior wall has all three aponeuroses, and there is no posterior wall.

What are the contents of the rectus sheath?

The rectus sheath contains the rectus abdominis and pyramidalis muscles, the superior and inferior epigastric arteries and veins, and the lower six thoracic nerves (T7–T12).

What is the clinical significance of the rectus sheath?

The rectus sheath is clinically significant for pedicle flap surgery in breast reconstruction, rectus sheath hematoma from trauma or coughing, and divarication of recti, which can cause hernias.

What is the arcuate line and why is it important?

The arcuate line is a landmark between the umbilicus and pubic symphysis that marks the lower limit of the posterior wall of the rectus sheath, below which there is no posterior wall.

How do the nerves and blood vessels relate to the rectus sheath?

The lower six thoracic nerves (T7–T12) enter the sheath through the posterior wall to supply the rectus abdominis. The superior and inferior epigastric arteries provide blood supply, entering via the diaphragm and anterior to the arcuate line, respectively.

Rectus Sheath – Formation, Layers & Contents