Structure
The rectus sheath is the fibrous covering that surrounds the rectus abdominis muscle. It is formed by the blending of the aponeuroses of the external abdominal oblique, internal abdominal oblique and the transversus abdominis muscles, and consists of anterior and posterior layers.
The anterior layer of the rectus sheath covers the entire length of the anterior aspect of the rectus abdominis muscle, where:
- its superior three quarters is formed by the aponeurosis of external abdominal oblique muscle and the anterior lamina of the aponeurosis of internal abdominal oblique muscle;
- its inferior one quarter is formed by the aponeuroses of external abdominal oblique, internal abdominal oblique and the transversus abdominis muscles.
The posterior layer of the rectus sheath only covers the superior two thirds of the posterior aspect of the rectus abdominis muscle, ending at the arcuate line. It is formed by the aponeurosis of transversus abdominis muscle and the posterior lamina of the aponeurosis of internal abdominal oblique muscle.
Along the midline, the anterior and posterior layers of the rectus sheath blend with each other and with the fibers of the contralateral rectus sheath, forming the linea alba (Moore, Dalley and Agur, 2009).
Related parts of the anatomy
Anatomical Relations
The rectus sheath contains the:
- rectus abdominis muscle;
- pyramidalis muscle;
- the terminal ends of the anterior rami of the seventh to twelfth thoracic nerves;
- the superior and inferior epigastric vessels.
The rectus sheath is located anterior to the transversalis fascia.
Function
The rectus sheath encloses the rectus abdominis and pyramidalis muscles. Both the rectus sheath and linea alba are the sites where the aponeuroses of the external abdominal oblique, internal abdominal oblique, and the transversus abdominis muscles blend together. They act as attachment sites for these muscles and allowing them to work in unison.
References
Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2009) Clinically Oriented Anatomy. Lippincott Williams & Wilkins.
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Rectus Sheath
The rectus sheath is the term used for the anatomic arrangement of the aponeuroses from the IAO, EAO and TAB around the RA.
