Latissimus Dorsi Muscle
Origin: Spinous processes of vertebrae T7-T12, Thoracolumbar fascia, Posterior third of crest of ilium, Ribs 9-12, Inferior angle of scapula
Insertion: Intertubercular groove of the humerus
Actions: Adducts, extends and internal rotation of the arm at the shoulder
Innervation: Thoracodorsal nerve (C6 – C8)
Blood Supply: Thoracodorsal artery from the axillary artery
Primary Actions of the Latissimus Dorsi Muscle
1. Adduction of the arm at shoulder
Agonists:
- Pectoralis Major
- Teres Major
- Triceps Brachii (long head)
Antagonists:
- Deltoid (middle)
- Supraspinatus
2. Extension of the arm at the shoulder
Agonists:
- Deltoid (posterior)
- Triceps brachii (long head)
- Pectoralis major (sternal head)
Antagonists:
- Deltoid (anterior)
- Biceps brachii
- Coracobrachialis
- Pectoralis Major (clavicular head)
3. Internal rotation of the arm at the shoulder
Agonists:
- Subscapularis
- Deltoid (anterior)
- Pectoralis major
- Teres major
Antagonists:
- Infraspinatus
- Teres minor
- Deltoid (posterior)
Secondary Actions of the Latissimus Dorsi:
1. Assists with extension of the trunk
Agonists:
- Longissimus thoracis
- Iliocostalis lumborum
- Iliocostalis thoracis
Antagonists:
- Rectus Abdominis
2. Assists with flexion of the trunk
Agonists:
- Rectus Abdominis
Antagonists:
- Longissimus thoracis
- Iliocostalis lumborum
- Iliocostalis thoracis
3. Assists with lateral flexion of the trunk
Agonists:
- Quadratus lumborum
- Rectus abdominis
Antagonists:
- Longissimus thoracis
- Iliocostalis lumborum
- Iliocostalis thoracis
4. Assists with anterior and lateral pelvic tilt
Agonists:
- Rectus abdominis
Antagonists:
- Semitendinosus
- Semimembranosus
- Biceps femoris
5. Assists with depression of the scapula
Agonists:
- Serratus anterior (lower part)
- Trapezius (lower part)
- Pectoralis minor
Antagonists:
- Levator scapulae
- Trapezius (upper part)
6. Assists with protraction of the scapula
7. Assists with deep inspiration and forced expiration
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