Muscle
External oblique
Superficial sheet linking the ribs to the abdominal wall
High-yield
A right external oblique helps turn the trunk left. Its aponeurosis also contains the superficial inguinal ring.
Overview
External oblique covers the lateral abdominal wall. Its muscle fibers become an aponeurosis toward the midline, transmitting force to the linea alba. Most fibers slope downward and medially; the lower aponeurotic margin forms the inguinal ligament.
Reference facts
- Origin
- Ribs 5–12, on their outer surfaces.
- Insertion
- The aponeurosis reaches the linea alba and pubic tubercle; muscular attachment also extends along the anterior iliac crest.
- Action
- Both sides compress the abdominal contents and assist trunk flexion; one side contributes to rotation away from that side.
- Innervation
- Thoracoabdominal nerves T7–T11 and the subcostal nerve, T12.
- Blood supply
- Segmental branches include lower posterior intercostal and subcostal arteries.
Clinical correlation
An inguinal hernia may extend through the superficial ring into superficial tissues. This opening belongs to the external oblique aponeurosis, whereas the canal's posterior wall lies deeper.
Frequently asked questions
What does the external oblique do?
Both sides compress the abdominal contents and assist trunk flexion; one side contributes to rotation away from that side.
What nerve innervates the external oblique?
The external oblique is innervated by the thoracoabdominal nerves T7–T11 and the subcostal nerve, T12.
Where does the external oblique attach?
Origin: Ribs 5–12, on their outer surfaces. Insertion: The aponeurosis reaches the linea alba and pubic tubercle; muscular attachment also extends along the anterior iliac crest.
What is the blood supply of the external oblique?
The external oblique is supplied by the segmental branches include lower posterior intercostal and subcostal arteries.