Posterior wall of rectus sheath (left), and transverse sections of rectus sheath at two different levels (A and B).

Posterior aspect of anterior abdominal wall removed from abdomen in illustration 2. 18A.

Transverse section of sheath of rectus abdominis (rectus sheath) superior to umbilicus. See arrow in illustration 2. 7A for orientation.

Posterior rectus sheath and inguinal canal. External oblique and its aponeurosis cut away to reveal the iliohypogastric and ilioinguinal nerves. Spermatic cord pulled medially to reveal genital branch of genitofemoral nerve.

Superficial dissection of trunk, lateral view, showing superficial nerves and muscles.

Transverse section of sheath of rectus abdominis (rectus sheath) inferior to umbilicus. See arrow in illustration 2. 7A for orientation.

Posterior view of the abdominal region illustrating the rectus abdominis (left) and transversus abdominis (right) muscles and their bony attachments.

Posterior view of the abdominal region illustrating the transversus abdominis muscle and its bony attachments. Both sides of muscle are shown.

Posterior view of the abdominal region illustrating the rectus abdominis muscle and its bony attachments. Muscles on both sides of the linea alba are shown.

Schematic of horizontal section of inguinal canal and testis. Drawing shows eight layers of abdominal wall and three evaginations: scrotum, coverings of spermatic cord, and constituents of the cord.

Transverse or horizontal (axial) MRI of the abdomen at the level of the lower L1. Image at bottom illustrates level of scan (line D).

Transverse or horizontal (axial) MRI of the abdomen at the level of the lower L3. Image at bottom illustrates level of scan (line F).

Rectus abdominis, action