Arcuate Line

Arcuate line is a margin that anatomically and visibly divides regions among organs, it is found in:

• Rectus sheath
• ilium

Rectus Sheath

The arcuate line differentiates the inferior margin of the posterior rectus sheath. In contrast, below the arcuate line, the aponeurosis of the internal oblique muscle contributes solely to the anterior rectus sheath.

Arcuate Line – Rectus Sheath

Relations

• Above the arcuate line, the aponeurosis contributes to the posterior rectus sheath along with the internal oblique; below the arcuate line, it joins the internal and external oblique to form the anterior rectus sheath.
• The aponeurosis of the internal oblique muscle works for both the anterior and posterior rectus sheaths above the arcuate line.
• The innermost muscular layer of the abdominal wall created by the transversus abdominis.
• The transversus abdominis travels transversely, medially contributing to the rectus sheath.
• The inferior edge of the transversus abdominis aponeurosis attaches on Cooper ligament, which is made up of periosteum and fascial concentrations along the posterior aspect of the superior pubic ramus.

Ilium

Anteriorly, the ridge separating the upper and lower parts of the ilium is rounded and termed the arcuate line.

Arcuate Line: Ilium

Relations

• The medial surface of the ilium is divided into two parts by the arcuate line.
  1. A concave surface called the iliac fossa is located above arcuate line.
  2. A flattened surface that is constant with the medial surfaces of the pubis and ischium is located below arcuate line.
• The arcuate line of the ilium forms the posterior part of the iliopectineal line and the pectineal line forms the anterior part of the iliopectineal line.
• The arcuate line forms part of the linea terminalis and the pelvic brim.

The pelvic part of the ilium that is located inferiorly towards the arcuate line adds to the wall of the lesser or true pelvis.