The rectus sheath is a fibrous structure formed by the aponeuroses (flat tendinous extensions) of the three anterolateral abdominal wall muscles — external oblique, internal oblique, and transverse abdominis — which interdigitate and unite in the midline (linea alba) after wrapping around the rectus abdominis muscle. The lateral boundary of this structure is marked by the semilunar lines, and the specific arrangement of which aponeurotic layers pass anterior versus posterior to rectus abdominis differs depending on whether the cross-section is taken above or below the umbilicus. This is gross anatomy of the abdominal wall, describing how individual muscle aponeuroses combine to form a compound fascial sheath enclosing a named muscle.
The rectus sheath is a fibrous structure formed by the aponeuroses (flat tendinous extensions) of the three anterolateral abdominal wall muscles — external oblique, internal oblique, and transverse a…