External abdominal oblique muscle

Last update: May 25th, 2023

The external abdominal oblique is a muscle located in the anterolateral abdominal wall. It belongs to a group that also includes the transversus abdominis, internal abdominal oblique, rectus abdominis, and pyramidalis muscles.

The primary functions of this muscle involve the flexion, rotation, and lateral flexion of the trunk. Additionally, it aids in increasing abdominal pressure in situations where it is needed, such as during coughing, labor, defecation, and more.

External abdominal oblique muscle
Origin	External surfaces of the ribs 5-12
Insertion	Linea alba; Pubic tubercle; Anterior half of the iliac crest
Innervation	Intercostal nerves T7-T11; Subcostal nerve (T12)
Functions	Lateral flexion of the trunk; Rotation of the trunk; Flexion of the trunk

In this article, we will discuss the anatomy and functions of the external oblique muscle.

External oblique muscle with labels: Deltoid, latissimus dorsi, external oblique, biceps brachii, abdominal aponeurosis, pectoralis major, serratus anterior

External oblique muscle with labels: Pectoralis minor, latissimus dorsi, external oblique, biceps brachii, rectus abdominis, serratus anterior, Linea alba

External oblique muscle with labels: External intercostals, internal intercostals, serratus anterior, external oblique, linea alba, rectus abdominis

External oblique muscle with labels: external oblique, linea alba, internal oblique, abdominal aponeurosis

External oblique muscle with labels: external oblique, linea alba, internal oblique, transversus abdominis, abdominal aponeurosis

Relations of the external abdominal oblique muscle

Origin and insertion

The external oblique muscle originates from the external surfaces of ribs 5-12. From there, it courses obliquely and inferiorly to insert onto structures on the midline of the body, including the linea alba, pubic tubercle, and anterior half of the iliac crest.

External Oblique highlighted and labeled

External Oblique with labels: Insertion and Origin

Origin and insertion of the external oblique muscle

Innervation

The external abdominal oblique is innervated by intercostal nerves T7-T11 and the subcostal nerve (T12). These nerves are essentially the anterior rami of the thoracic spinal nerves.

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Functions

Depending on whether both or only one muscle contracts, the external oblique performs several functions:

Unilateral contraction (from one side) results in the lateral flexion of the trunk to the same side.

First image in animation of a figure with lateral flexion

Second image in animation of a figure with lateral flexion

Third image in animation of a figure with lateral flexion

Fourth image in animation of a figure with lateral flexion

Fifth image in animation of a figure with lateral flexion

Lateral flexion of the trunk

When unilateral contraction is paired with the contraction of the internal abdominal oblique from the opposite side, it produces rotation of the trunk to the opposite side.

First image in animation of a figure with a rotated vertebral column

Second image in animation of a figure with a rotated vertebral column

Third image in animation of a figure with a rotated vertebral column

Fourth image in animation of a figure with a rotated vertebral column

Rotation of the trunk

When both muscles contract (bilateral contraction), it leads to the flexion of the trunk. This movement helps increase intraabdominal pressure.

First image in animation of a figure with a flexed vertebral column

Second image in animation of a figure with a flexed vertebral column

Third image in animation of a figure with a flexed vertebral column

Fourth image in animation of a figure with a flexed vertebral column

Flexion of the trunk

An Overview of the External Oblique Muscle

Muscles That Act On Abdominal Wall

Test yourself on external oblique muscle with answers hidden

Test yourself on external oblique muscle with answers shown:Deltoid, pectoralis major, latissimis dorsi, serratus anterior, biceps brachii, external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown:Pectoralis major, latissimis dorsi, serratus anterior, biceps brachii, external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown:Pectoralis minor, latissimis dorsi, serratus anterior, biceps brachii, external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown: :External intercostals, internal intercostals, serratus anterior, external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown:External intercostals, internal intercostals, external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown: Internal intercostals, external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown: external oblique, linea alba, rectus abdominis, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown: external oblique, linea alba, abdominal aponeurosis

Test yourself on external oblique muscle with answers shown: external oblique, linea alba, internal oblique, abdominal aponeurosis

Test yourself while observing the external oblique muscle anatomy

References

Open Anatomy. (n.d.). TA2 Viewer. Retrieved April 5, 2023, from https://ta2viewer.openanatomy.org/
Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., & Kruse, D. H. (2022). Anatomy and Physiology (2nd ed.). OpenStax. https://openstax.org/details/books/anatomy-and-physiology-2e
Palastanga, N., & Soames, R. (2012). Anatomy of Human Movement (6th ed.). Edinburgh, Scotland: Churchill Livingstone.
Moore, K. L. (2018). Clinically Oriented Anatomy (8th ed.). Philadelphia, PA: Wolters Kluwer.
Drake, R. L., Vogl, A. W., & Mitchell, A. W. M. (2015). Gray’s Anatomy for Students (3rd ed.). Edinburgh, Scotland: Churchill Livingstone.