Linea alba (abdomen) From Wikipedia, the free encyclopedia Jump to: navigation, search Linea alba Diagram of sheath of Rectus. The Obliquus externus abdominis. Gray's subject #118 417 Dorlands/Elsevier l_10/12496016 The linea alba is a fibrous structure that runs down the midline of the abdomen in humans and other vertebrates. The name means white line and the linea alba is indeed white, being c..