The arcuate line of rectus sheath (the arcuate line or the semicircular line of Douglas) is a line of demarcation corresponding to the free inferior margin of the posterior layer of the

rectus sheath The rectus sheath (also called the rectus fascia.) is a tough fibrous compartment formed by the aponeuroses of the transverse abdominal, transverse abdominal muscle, and the internal oblique, internal and external oblique muscles. It contains the ...

inferior to which only the anterior layer of the rectus sheath is present and the rectus abdominis muscle is therefore in direct contact with the

transversalis fascia The transversalis fascia (or transverse fascia) is the fascial lining of the anterolateral abdominal wall situated between the inner surface of the transverse abdominal muscle, and the preperitoneal fascia. It is directly continuous with the ilia ...

. The arcuate line is concave inferior-wards. The arcuate line is visible upon the inner surface of the abdominal wall. The arcuate line may be a well-defined, or may be represented by a gradual waning of the aponeurotic fibres with concomitant increasing prominence of the

. The arcuate line occurs about midway between the umbilicus and

pubic symphysis The pubic symphysis (: symphyses) is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attache ...

, however, this varies from person to person. The

inferior epigastric artery In human anatomy, the inferior epigastric artery is an artery that arises from the external iliac artery. It is accompanied by the inferior epigastric vein; inferiorly, these two inferior epigastric vessels together travel within the lateral um ...

and

vein Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and feta ...

pass across the arcuate line to enter the rectus sheath.

Anatomy

Superior to the arcuate line, the internal oblique muscle

aponeurosis An aponeurosis (; : aponeuroses) is a flattened tendon by which muscle attaches to bone or fascia. Aponeuroses exhibit an ordered arrangement of collagen fibres, thus attaining high tensile strength in a particular direction while being vulnerable ...

splits to envelop the

rectus abdominis muscle The rectus abdominis muscle, () also known as the "abdominal muscle" or simply better known as the "abs", is a pair of segmented skeletal muscle on the ventral aspect of a person's abdomen. The paired muscle is separated at the midline by a ba ...

both anteriorly and posteriorly. The anterior layer is derived from the

external oblique The abdominal external oblique muscle (also external oblique muscle or exterior oblique) is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. Structure The external oblique is situated on the lateral ...

and the anterior lamina of the

internal oblique The abdominal internal oblique muscle, also internal oblique muscle or interior oblique, is an abdominal muscle in the abdominal wall that lies below the external oblique muscle and just above the transverse abdominal muscle. Structure Its fiber ...

aponeurosis. The posterior layer is made up of the posterior lamina of the internal oblique aponeurosis and the transversus abdominis aponeurosis. Inferior to the arcuate line, the aponeuroses of the

external oblique muscle The abdominal external oblique muscle (also external oblique muscle or exterior oblique) is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. Structure The external oblique is situated on the lateral ...

, the internal oblique muscle, and the

transversus abdominis muscle The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall, deep to (layered below) the inter ...

merge and pass superficial to the

. Therefore, inferior to the arcuate line, the rectus abdominis rests directly on the

Clinical significance

Spigelian hernias and, exceedingly rarely, arcuate line hernias may occur inferior to the arcuate line. The arcuate line must be incised at its lateral-most point in order to enter the

space of Retzius Retropubic space is a potential avascular space located between the pubic symphysis and the urinary bladder. The retropubic space is a preperitoneal space, located behind the transversalis fascia and in front of peritoneum. Other names for the r ...

and space of Bogros from within the rectus sheath during surgery during retrorectus repair and transversus abdominis release.

History

The arcuate line is also known as the linea semicircularis, and the semicircular line of Douglas.

References

External links

* - "Anterior Abdominal Wall: The Posterior Wall of the Rectus Sheath" * * * * * - "Anterior Abdominal Wall, Lower Part, Posterior View" {{Authority control Abdomen