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MSAK101-II – Session 2 – Shoulder Muscles

BLUE SKY SCHOOL OF PROFESSIONAL MASSAGE AND

THERAPEUTIC BODYWORK

Musculoskeletal Anatomy & Kinesiology II

SHOULDER GIRDLE MUSCLES

MSAK101-II Session 2

LEARNING OBJECTIVES:

By the end of this session, the student will be expected to:

1. Apply all review material.

2. List and describe new structures.

3. For the muscles of the shoulder muscles:

a. Locate.

b. Identify attachments points.

c. Demonstrate fiber direction.

d. List actions.

e. Describe relationship or layering to other musculoskeletal structures.

f. Palpate.

1) POSTERIOR SHOULDER GIRDLE MUSCLES:

a) Trapezius

i) Upper Trapezius

(1) Origin: External occipital protuberance, Nuchal ligament.

(2) Insertion: Lateral third of clavicle, acromion process.

(3) Fiber Direction: Superior to inferior at an angle laterally.

(4) Actions:

(a) Elevation of scapula.

(b) Upward rotation of scapula

(c) Unilateral lateral flexion of neck

(d) Bilateral extension of head and neck.



ii) Middle Trapezius

(1) Origin: SP’s of T1-T5.

(2) Insertion: Medial border of the acromion process and

the spine of scapula.

(3) Fiber Direction: Medial to lateral.

(4) Action: Retraction of scapula.

iii) Lower Trapezius


(2) Insertion: Root of the spine of scapula.

(3) Fiber Direction: Inferior to superior at a lateral angle.

(4) Actions:

(a) Depression and retraction of scapula

(b) Upward rotation of scapula.

b) Levator Scapulae

i) Origin: TP’s of C1-C4.

ii) Insertion: Vertebral border of scapula from the superior

angle to the root of the scapular spine.

iii) Fiber Direction: Superior to inferior at an angle laterally.

iv) Actions:

(1) Elevation of the scapula

(2) Downward rotation of scapula

(3) Lateral flexion of neck

(4) Extension of neck.

v) Notes / relationship to other musculoskeletal structures:

(1) At its scapular attachment, the Levator is deep

only to the Trapezius.

(2) At its TP attachments, Levator is deep to the

Splenius capitis and the SCM.



c) Rhomboids

i) Rhomboid Minor

(1) Origin: SP’s of C7-T1.

(2) Insertion: Root of the spine of scapula.

(3) Fiber Direction: Superior to inferior at

an angle laterally.

(4) Actions:

(a) Retraction of the scapula.

(b) Elevation of the scapula.

(c) Downward rotation of the scapula.

(5) Notes / relationship to other musculoskeletal structures:

(a) The rhomboids are deep to the Trapezius.

(b) Rhomboid minor is directly superior to Rhomboid major.

(c) Rhomboid minor is directly inferior to Levator’s attachment.

ii) Rhomboid Major


(2) Insertion: Vertebral border of scapula from

root of the spine to the inferior angle.

(3) Fiber Direction: Superior to inferior at

an angle laterally.

(4) Actions:

(a) Retraction of the scapula.

(b) Elevation of the scapula.

(c) Downward rotation of scapula.


(a) When the Rhomboids are weak, they can contribute

to a “rounded shoulder” type appearance because they

(b) are unable to oppose protraction and depression of the scapulae.



2) ANTERIOR SHOULDER GIRDLE MUSCLES:

a) Serratus Anterior

i) Origin: Outer surface of ribs 1-9.

ii) Insertion: Anterior surface of the vertebral border of scapula.

iii) Fiber Direction: Lateral to medial.

iv) Actions:

(1) Protraction of scapula.

(2) Upward rotation of scapula.

(3) Stabilizes scapula against the chest wall.


(1) Posteriorly, Serratus anterior lies deep to the scapula.

Anteriorly, it is deep to the Pectoralis major and minor.

(2) The lowest slips of costal attachments interdigitate with the external obliques.

(3) Serratus anterior lies anterior to Subscapularis.

b) Pectoralis Minor

i) Origin: Anterior ribs 3-5 near the

costal cartilages.

ii) Insertion: Coracoid process of the scapula.

iii) Fiber Direction: Inferior to superior at lateral angle.

iv) Actions:

(1) Protraction of the scapula.

(2) Depression of the scapula.

(3) Downward rotation of scapula.


(1) Pectoralis minor is deep to Pectoralis major.

(2) Deep to Pectoralis minor are Serratus anterior and the ribcage.

(3) Pectoralis minor is one of three muscles that attach to the coracoid process.



c) Subclavius

i) Origin: First rib at costal cartilage (costochondral)

junction.

ii) Insertion: Middle third of inferior shaft of clavicle.

iii) Fiber Direction: Medial to lateral.

iv) Actions:

(1) Depression of clavicle.

(2) Stabilizes clavicle by moving it medially


(1) Subclavius is deep to the Pectoralis major.

(2) Deep to Subclavius are the brachial plexus and the subclavian artery and vein.

3) SHOULDER MUSCLES:

a) Deltoid

i) Origin:

(1) Anterior – Lateral third of clavicle.

(2) Middle - Lateral acromion process.

(3) Posterior – Spine of scapula.

ii) Insertion: Deltoid tuberosity.

iii) Fiber Direction: Generally, medial to lateral.

iv) Actions: (All of glenohumeral joint)

(1) Anterior – Flexion, abduction, horizontal adduction,

internal rotation

(2) Middle – Abduction to 90 degrees.

(3) Posterior – Extension, abduction, horizontal abduction, external rotation.


(1) Deltoid is superficial gives the shoulder its characteristic shape.

b) Coracobrachialis

i) Origin: Coracoid process of scapula.

ii) Insertion: Medial middle third of shaft of humerus.

iii) Fiber Direction: Superior to inferior at an angle laterally.




(1) Flexion.

(2) Adduction.


(1) This is one of three muscles that attach to the coracoid

process of the scapula. The other two are the short

head of the Biceps and the Pectoralis minor.

c) Latissimus Dorsi

i) Origin: Thoracolumbar aponeurosis, SP’s of T7-12, Sacrum, Iliac crest, Ribs 9-12

ii) Insertion: Medial lip of the bicipital groove of humerus.

iii) Fiber Direction: Inferior to superior at lateral angle.


(1) Extension.

(2) Internal rotation.

(3) Adduction.


(1) Teres major and Latissimus dorsi both attach onto the

medial lip of the biciptial groove.

d) Teres Major

i) Origin: Lower third of lateral border of scapula

just superior to inferior angle.

ii) Insertion: Medial lip of the bicipital groove.

iii) Fiber Direction: Inferior to superior at a lateral angle.


(1) Extension.


(3) Adduction.


(1) Teres major and the Latissimus dorsi both attach onto the medial lip of the bicipital groove.

(2) Teres major is sometimes referred to as “Lat’s little helper”



e) THE ROTATOR CUFF (SITS Group)

i) Supraspinatus

(1) Origin: Supraspinous fossa of scapula.

(2) Insertion: Superior portion of greater tubercle of humerus.

(3) Fiber Direction: Generally, medial to lateral.

(4) Actions:

(a) Abduction of glenohumeral joint.

(b) Maintains vertical traction of the head of humerus

helping to hold the head in the glenoid fossa.


(a) “S” in “SITS”.

(b) The only rotator cuff muscle that does not contribute to rotation of arm.

(c) Supraspinatus is the most commonly injured of the rotator cuff musculature.

Infraspinatus

(6) Origin: Infraspinous fossa of scapula.

(7) Insertion: Posterior surface of greater tubercle of humerus.

(8) Fiber Direction: Medial to lateral at an angle superiorly.

(9) Actions: (All of glenohumeral joint)

(a) Extension.

(b) External rotation.

(c) Horizontal adduction.


(a) “I” in “SITS”.

ii) Teres Minor

(1) Origin: Upper lateral border of scapula.

(2) Insertion: Inferior facet of greater tubercle of humerus.

(3) Fiber Direction: Medial to lateral at an angle superiorly.

(4) Actions: (All of glenohumeral joint)

(a) Extension

(b) External rotation

(c) Horizontal adduction.


(a) “T” in “SITS”.

(b) On the scapula, the Teres minor attaches superiorly to Teres major.



iii) Subscapularis

(1) Origin: Entire anterior surface of the subscapular fossa.

(2) Insertion: Lesser tubercle of humerus.

(3) Fiber Direction: Medial to lateral.

(4) Action: (All of glenohumeral joint)

(a) Internal rotation.


(a) The Second “S” in “SITS”.

(b) Subscapularis is deep to scapula and superficial to

Serratus Anterior and the ribcage.

(c) Only rotator cuff muscle to attach to lesser tubercle and to rotate the arm internally.

f) Pectoralis Major

i) Origin:

(1) Clavicular head – medial half of anterior clavicle.

(2) Sternal head – sternum and cartilages of ribs 1-6.

ii) Insertion: Lateral lip of the bicipital groove.

iii) Fiber Direction: Generally from medial to lateral.


(1) Adduction.

(2) Horizontal adduction.


(4) Flexion.

(5) Extension


(1) Pectoralis major is a superficial chest muscle.

g) Biceps and Triceps (Covered Next Session)



4) MOTION OF SHOULDER GIRDLE

ACTION

AGONIST SYNERGIST

Elevation Upper Trapezius

Levator Scapulae

Rhomboids

Depression Lower Trapezius Pectoralis Minor

Retraction Rhomboids Middle Trapezius

Protraction Serratus Anterior Pectoralis Minor

Upward Rotation Lower and Upper Trap

Serratus Anterior

Downward Rotation Pectoralis Minor Rhomboids

Levator Scapulae

5) MOTION OF SHOULDER

ACTION

Normal ROM AGONIST SYNERGIST

Flexion 180° Anterior Deltoid

Coracobrachialis

Pectoralis Major

Biceps Brachii

Extension 45° Latissimus Dorsi

Posterior Deltoid

Teres Major

Triceps Brachii

Adduction 45° Pectoralis Major

Latissimus Dorsi

Ant and Post Deltoid

Coracobrachials

Teres Major

Abduction 180° Middle Deltoid

Supraspinatus

External rotation 40 - 45° Infraspinatus

Teres Minor

Posterior Deltoid

Internal rotation 55° Subscapularis

Pectoralis Major

Latissimus Dorsi

Teres Major

Anterior Deltoid

Horizontal Adduction Pectoralis Major

Coracobrachialis

Anterior Deltoid

Bicheps Brachii

Horizontal Abduction Posterior Deltoid

Infraspinatus

Latissimus Dorsi

Teres Minor

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