1b - Muscles Involved in Movement of the Scapula

Question 1

Pectoralis minor - Origin, Insertion, Action, and Innervation

Answer 1

Origin: Anterior surface of ribs 3-5
Insertion: Coracoid process of scapula
Primary action: When ribs are fixed, it protracts and rotates scapula downwards.
Other action(s): When scapula is fixed, pulls ribs superiorly.
Innervation: Medial Pectoral

Question 2

Serratus anterior - Origin, Insertion, Action, and Innervation

Answer 2

Origin: Series of muscle slips from ribs 1-8
Insertion: Entire anterior surface of vertebral (medial) border of scapula.
Primary action: Rotate scapula upward.
Other action(s): Prime mover to protract and hold scapula against chest wall. Called ‘boxer’s muscle’ because it’s important in abduction and raising of arm in horizontal movements (pushing, punching)
Innervation: Long Thoracic

Question 3

Subclavius - Origin, Insertion, Action, and Innervation

Answer 3

Origin: Cartilage of first rib
Insertion: Groove on inferior surface of clavicle.
Primary action: Helps stabilize and depress pectoral girdle.
Innervation: Subclavian

Question 4

Trapezius - Origin, Insertion, Action, and Innervation

Answer 4

Origin: Occipital bone, ligamentum nuchae and spines of C7 and T1-12
Insertion: Continuous insertion on acromion and spine of scapula as well as the lateral third of the clavicle.
Primary action: Stabilizes, elevates, retracts, and rotates scapula.
Other action(s): Superior fibers elevate the scapula (shrugging) or extend head when scapula is fixed. Middle fibers adduct the scapula. Inferior fibers depress the scapula (and shoulders).
Innervation: Spinal Accessory (CN XI)

Question 5

Levator scapulae - Origin, Insertion, Action, and Innervation

Answer 5

Origin: Transverse processes of C1 - C4
Insertion: Medial border of the scapula superior to the spine. Insertion is superior to rhomboids.
Primary action: Elevates and adducts scapula. Synergizes with superior fibers of Trapezius muscle.
Other action(s): Rotate scapula downwards. When scapula is fixed, flexes neck to same side.
Innervation: Dorsal Scapular

Question 6

Rhomboids - Origin, Insertion, Action, and Innervation

Answer 6

Origin: Spinous process of C7 and T1 (minor) and of T2 - T5 (major)
Insertion: Medial border of scapula inferior to levator scapulae.
Primary action: Stabilize scapula.
Other action(s): Acts with middle Trapezius muscle fibers to retract scapula (square shoulders). Rotates scapula downwards (with levator scapulae).
Innervation: Dorsal Scapular

Question 7

What is/are the major muscle(s) in scapula elevation?

Answer 7

Done by muscles that run inferolaterally. Primarily by the Levator Scapulae and superior Trapezius muscle fibers. Rhomboids are synergists.

Question 8

What is/are the major muscle(s) in scapula depression?

Answer 8

The Serratus Anterior, Pectoralis Minor, and inferior fibers of Trapezius muscle.

Question 9

What is/are the major muscle(s) in scapula protraction/abduction?

Answer 9

Primarily the Serratus Anterior muscle (the boxer’s muscle).

Question 10

What is/are the major muscle(s) in scapula retraction/adduction?

Answer 10

Middle fibers of Trapezius and the Rhomboid muscles.

Question 11

What is/are the major muscle(s) in scapula upward rotation?

Answer 11

The Serratus Anterior muscle pulls the inferior angle of the scapula laterally, while the Trapezius muscle pulls the superior angle of the scapula medially.

Question 12

What is/are the major muscle(s) in scapula downward rotation?

Answer 12

The Rhomboid muscles pull the inferior angle of the scapula medially, while the levator scapulae steadies the superior angle.