Lower lateral

Oblique Muscles: Anatomy and Clinical Significance

Introduction

The oblique muscles of the abdomen include the external oblique and internal oblique muscles. They are key components of the lateral abdominal wall, playing vital roles in trunk rotation, lateral flexion, and maintaining abdominal pressure.

External Oblique Muscle

Origin

• Lower eight ribs (ribs 5-12): The anterior borders of ribs 5-12.

Insertion

• Linea alba: Via the aponeurosis.
• Pubic tubercle and anterior superior iliac spine (ASIS): Via the external oblique aponeurosis.

Innervation

• Thoracoabdominal nerves (T7-T11): Main supply.
• Subcostal nerve (T12): Also supplies part of the muscle.

Function

• Contralateral rotation of the trunk: When one side contracts, it rotates the trunk to the opposite side.
• Lateral flexion: Bending the trunk sideways.
• Compression of abdominal contents: Assists in increasing intra-abdominal pressure.

Internal Oblique Muscle

Origin

• Thoracolumbar fascia: The deep back fascia.
• Anterior two-thirds of the iliac crest:
• Inguinal ligament:

Insertion

• Lower ribs (ribs 10-12): Ribs 10-12 via the aponeurosis.
• Linea alba: Via the internal oblique aponeurosis.
• Pubic crest and pecten pubis:

Innervation

• Thoracoabdominal nerves (T7-T11):
• First lumbar nerve (L1):

Function

• Ipsilateral rotation of the trunk: Rotates the trunk to the same side.
• Lateral flexion:
• Supports abdominal wall: Assists in compressing abdominal contents and respiration.

Clinical Significance

Injuries and Disorders

• Muscle strain: Common in athletes performing twisting movements.
• Oblique muscle tear: Causes pain and weakness in trunk rotation and lateral bending.
• Hernias: Inguinal hernias may be related to weakness in the oblique muscles, especially the internal oblique.

Signs and Symptoms

• Lower lateral abdominal pain.
• Difficulty rotating or bending the trunk.

Management

Rest, physiotherapy, and in some cases surgical repair for hernias or severe tears.

Related Structures

• Linea alba: The fibrous structure where aponeuroses of oblique muscles meet in the midline.
• Inguinal ligament: A fibrous band from the anterior superior iliac spine to the pubic tubercle, serving as an attachment point.
• Pelvis and lower ribs: Points of origin and insertion.

Summary

The external and internal oblique muscles are essential components of the lateral abdominal wall, contributing to trunk movement, stabilization, and increasing intra-abdominal pressure. Knowledge of their anatomy is vital for diagnosing abdominal and lumbar injuries and understanding core stability.

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