In human anatomy, the anterolateral abdominal wall is composed of layered muscles — external oblique, internal oblique, transversus abdominis, and rectus abdominis — whose fiber orientations, origins, insertions, and innervation (thoracoabdominal and subcostal nerves, T6–T12) determine their shared functions of trunk flexion/rotation and compression of abdominal viscera to support intra-abdominal pressure and the vertebral column. These muscles' flattened tendons (aponeuroses) interdigitate around rectus abdominis to form the rectus sheath, whose composition differs above versus below the arcuate line (umbilicus region): above, the internal oblique aponeurosis splits into anterior and posterior laminae, while below, all three aponeuroses pass anterior to rectus abdominis, leaving only transversalis fascia posteriorly. This concept belongs to abdominal wall anatomy and relates to the broader discipline by establishing the muscular and fascial architecture that also delineates the inguinal canal.
In human anatomy, the anterolateral abdominal wall is composed of layered muscles — external oblique, internal oblique, transversus abdominis, and rectus abdominis — whose fiber orientations, origins…