The Obliquus externus abdominis. (Linea semilunaris labeled vertically at center, at border between brown and gray.)
Linea semilunares are at lateral borders of rectus abdominis.
Each corresponds with the lateral border of the rectus abdominis, extends from the cartilage of the ninth rib to the pubic tubercle, and is formed by the aponeurosis of the internal oblique at its line of division to enclose the rectus, reinforced anteriorly by the external oblique and posteriorly by the transversus abdominis above the arcuate line (also known as linea semicircularis or Douglas' line).
A hernia through the linea semilunaris is called a Spigelian hernia, which is also referred to as a spontaneous lateral ventral hernia.
- Anatomy photo:35:06-0102 at the SUNY Downstate Medical Center - "The Linea Alba and Linea Semilunaris"
- Atlas image: abdo_wall52 at the University of Michigan Health System - "Insertions of Rectus Abdominis, Anterior View"