Rectus Abdominis

Abdomen · Trunk

Rectus Abdominis belongs to the Abdomen group of the Trunk. Originating at Pubic crest, pubic tubercle, and pubic symphysis, it inserts at Xiphoid process and costal cartilages of ribs 5–7. It is responsible for several movements: Flexion of trunk; compresses abdominal viscera; stabilizes pelvis. Its nerve supply is the Thoracoabdominal nerves, anterior rami of T7–T12.

Origin, Insertion, Action & Nerve

Origin

Pubic crest, pubic tubercle, and pubic symphysis

Insertion

Xiphoid process and costal cartilages of ribs 5–7

Action

Flexion of trunk; compresses abdominal viscera; stabilizes pelvis

Nerve

Thoracoabdominal nerves, anterior rami of T7–T12

Attachments explained

The Rectus Abdominis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Origin

Pubic crest, pubic tubercle, and pubic symphysis

Insertion

Xiphoid process and costal cartilages of ribs 5–7

Action & function

When the Rectus Abdominis contracts, it produces the following movements: Flexion of trunk; compresses abdominal viscera; stabilizes pelvis.

As part of the Abdomen group of the Trunk, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Rectus Abdominis receives its nerve supply from the Thoracoabdominal nerves, anterior rami of T7–T12. This nerve carries fibres from spinal segment(s) T7, T12.

Because a muscle can only contract when its nerve is intact, injury to the Thoracoabdominal nerves, anterior rami of T7–T12 or to its spinal roots (T7, T12) can weaken or paralyse the Rectus Abdominis, impairing the movements it normally produces (flexion of trunk). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Rectus Abdominis (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Rectus Abdominis, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Rectus Abdominis fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.