Arcuate Line of Pelvis
The structure indicated is the arcuate line of the pelvis.
The pelvic bones consist of three parts:
The arcuate line is found on the medial surface of the ilium. The ilium is the most superiorly positioned bone of the pelvis. The medial surface of the ilium is divided into superior and inferior parts by a ridge – the anterior part of this ridge is known as the arcuate line and forms part of the border of the pelvic inlet. The arcuate line lies below the iliac fossa, and below the iliacus muscle of the pelvis. The pectineal line and arcuate line collectively form the iliopectineal line.
Learn more about the bones of the pelvis in this anatomy tutorial.