External Oblique Muscle: Actions, Anatomy, and Clinical Significance

Action: Flexes the trunk from the side and rotates it ipsilateral. The external oblique muscles bilaterally act to flex the spine forward. These muscles work along with rectus abdominis and internal obliques to produce crunch movement

Innervation: Lower six thoracic nerves T7-T12.

Blood supply: Thoracoacromial, lateral thoracic, superficial and deep epigastric and lumbar arteries.

Clinical Relevance:

- Rhomboid major (RM): Scapular adduction, Retraction, and Downward rotation of scapula.

- Levator scapulae (LS): Elevation and upward rotation of scapula.

- Scalenes (S): Flexion of the neck, Lateral flexion and rotation to the ipsilateral side

- Pectoralis major (PM): Adduction, Medial rotation, and Flexion (sternal fibers only)

- Pectoralis minor (Pec.min): Protraction and depression of the shoulder joint

- Serratus anterior (SA): Protraction, Upward rotation, and Lateral rotation of scapula.

- Trapezius (TP): Upper, middle, and lower fibers have separate functions.

- Upper: Elevation and retraction of the scapula.

- Middle: Retraction of the scapula.

- Lower: Depression and retraction of the scapula

- Latissmus dorsi (LD): Extension, Adduction, and Medial rotation of the shoulder joint.