Rectus Abdominis Muscle
External abdominal oblique muscle
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|
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.
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.
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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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.
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.
When both muscles contract (bilateral contraction), it leads to the flexion of the trunk. This movement helps increase intraabdominal pressure.
An Overview of the External Oblique Muscle
Muscles That Act On Abdominal Wall
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- Palastanga, N., & Soames, R. (2012). Anatomy of Human Movement (6th ed.). Edinburgh, Scotland: Churchill Livingstone.
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