Latissimus Dorsi Anatomy: Origin, Insertion, Action, Innervation

Latissimus Dorsi Anatomy Study

Latissimus Dorsi Anatomy
Origin: Spinous processes of thoracic T7-T12, 9th to 12th ribs, the lumbar and sacral vertebrae (via the thoracolumbar fascia), and the posterior third of the external lip of the iliac crest. Occasionally by a slip from the posterior surface of the inferior angle of the scapula.
Insertion: Ends as a flattened tendon in front of the attachment of teres major to the floor of the bicipital groove of the humerus. As the muscle curves around the inferolateral border of teres major, the fiber bundles of latissimus dorsi rotate around each other, so that fibers that originate lowest insert highest on the humerus, and fibers that originate highest insert lowest on the humerus.
Action: Adducts, extends and internally rotates the arm at the shoulder
Innervation: Thoracodorsal nerve (C6 – C8)
Blood Supply:  Thoracordosal Artery from the axillary artery

Synergist: Pectoralis major and minor, Subclavius, Serratus anterior, Trapezius, Rhomboid major and minor, Levator scapulae.

Antagonist: Deltoid, Supraspinatus, Infraspinatus, Teres major and minor, Subscapularis

 

 

Primary Actions of the Latissimus Dorsi

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

    • Angonists: Deltoid (posterior) Triceps brachii (long head), pectoralis major (sternal head)
    • Antagonists: Deltoid (anterior) Biceps brachii, Coracobrachialis, Pectorial 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

    • Agonist: Rectus abdominis
    • Antagonists: Longissimus thoracis, Iliocostalis lumborum, Iliocostalis thoracis

3. Assists with lateral flexion of the trunk

    • Agonist: Quadratus lumborum, Rectus abdominis
    • Antagonists: Longissimus thoracis, Iliocostalis lumborum, Iliocostalis thoracis

4. Assists with anterior and lateral pelvic tilt

    • Agonist: Rectus abdominis
    • Antagonists: Semitendinosus, Semimembranosus, Biceps femoris

5. Assists with depression of the scapula

    • Agonists: Serratus Anterior (lower fibers), Trapezius (lower fibers), Pectoralis minor
    • Antagonists: Levator Scapulae, Trapezius (upper fibers)

6. Assist with protraction of the scapula

7. Assists with deep inspiration and forced expiration

For more information see:  Latissimus Dorsi Muscle: Shoulder, Arm, Low Abdominal, Pain 


An Anatomy Book That Uses Live Human Bodies And Muscle Overlays For Pictures That Allow You See Exact Muscle Location

basic_clinical_massa
Out of the scores of books in my office Basic Clinical Massage Therapy is by far the most referenced book in my library. The musculoskeletal system is overlaid on human models allowing you to learn the precise location, origin and insertions of each muscle. The models are pictured in various poses throughout the book which also helps you visualize muscles in motion and their actions relationship with the skeletal structure and other muscles. Though it is written for massage therapists, it is an excellent book for anyone who wants to learn about the muscular system. MT’s will benefit from recommended treatments for each muscle.


References:

The Trigger Point Therapy Workbook – Claire Davies, Amber Davies, and David G. Simons

Basic Clinical Massage Therapy: Integrating Anatomy and Treatment – James H. Clay and David M. Pounds

Trigger Point Therapy for Myofascial Pain – Donna Finando and Steven Finando

Massage Therapy Principles and Practice – Susan Salvo

Theory & Practice of Therapeutic Massage – Mark Beck

 

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