Chapter 2: Shoulder & Arm - Origins, Insertions and Actions - Pt 1 - V2

What is the origin of the deltoid muscle?

Lateral one-third of clavicle, acromion, and spine of scapula

Where does the deltoid muscle insert?

Deltoid tuberosity of the humerus

What action do all fibers of the deltoid muscle share?

Abduct shoulder at glenohumeral joint

What actions do the anterior fibers of the deltoid muscle perform?

Flex shoulder, medially rotate, horizontally adduct

What actions do the posterior fibers of the deltoid muscle perform?

Extend shoulder, laterally rotate, horizontally abduct

Which nerve innervates the deltoid muscle?

Axillary nerve

What is the origin of the trapezius muscle?

External occipital protuberance, medial portion of superior nuchal line of occiput, ligamentum nuchae, spinous processes of C7 through T12

What is the insertion of the trapezius muscle?

Lateral one-third of clavicle, acromion, and spine of scapula

What are the actions of the upper fibers of the trapezius muscle?

Bilaterally extend the head and neck; unilaterally: laterally flex head and neck to same side, rotate head and neck to opposite side, elevate scapula, upwardly rotate scapula

What are the actions of the middle fibers of the trapezius muscle?

Adduct the scapula, stabilize the scapula

What are the actions of the lower fibers of the trapezius muscle?

Depress the scapula, upwardly rotate the scapula

What is the nerve supply of the trapezius muscle?

Spinal portion of the CN XI accessory and ventral ramus

What is the origin of the Latissimus Dorsi?

Inferior angle of the scapula, spinous processes of last six thoracic vertebrae, last 3-4 ribs, thoracolumbar fascia, posterior iliac crest

Where does the Latissimus Dorsi insert?

Intertubercular groove of the humerus

What are the actions of the Latissimus Dorsi?

Extend shoulder, adduct shoulder, medially rotate shoulder

What nerve innervates the Latissimus Dorsi?

Thoracodorsal

What is the origin of the Teres Major?

Inferior angle and lower one-third of lateral border of the scapula

Where does the Teres Major insert?

Crest of the lesser tubercle of the humerus

What is the action of the Teres Major?

Extend the shoulder (GH), adduct the shoulder (GH), medially rotate the shoulder

Which nerve innervates the Teres Major?

Lower subscapular nerve

What muscle would be a synergist with teres major?

Latissimus Dorsi

What is the rotator cuff?

a group of 4 muscles that S-I-T-S around the shoulder and serves to stabilize the glenohumeral joint

What 4 muscles make up the rotator cuff?

supraspinatus, infraspinatus, teres minor, subscapularis

What is the origin of the supraspinatus muscle?

Supraspinous fossa of the scapula

Where does the supraspinatus muscle insert?

Superior facet of the greater tubercle of the humerus

What is the primary action of the supraspinatus muscle?

Abduct the shoulder

What nerve innervates the supraspinatus muscle?

Suprascapular nerve

What additional role does the supraspinatus play in shoulder movement?

Assists the deltoid with abduction of the shoulder

What is unique about the supraspinatus compared to other rotator cuff muscles?

It is the only muscle of the rotator cuff not involved in rotation

To what degree can the supraspinatus abduct the shoulder unassisted?

90 degrees

What is the origin of the Infraspinatus muscle?

Infraspinous fossa of the scapula

Where does the Infraspinatus muscle insert?

Middle facet of the greater tubercle of the humerus

What is the action of the Infraspinatus muscle?

Laterally rotate the shoulder, adduct the shoulder, and stabilize the head of humerus

Which nerve innervates the Infraspinatus muscle?

Suprascapular nerve

What is the origin of the Teres Minor?

Upper two-thirds of lateral border of the scapula

Where does the Teres Minor insert?

Inferior facet of the greater tubercle of the humerus

What is the action of the Teres Minor?

Laterally rotate the shoulder, adduct the shoulder and stabilize the head of humerus

Which nerve innervates the Teres Minor?

Axillary

What is the origin of the subscapularis muscle?

Subscapular fossa of the scapula

Where does the subscapularis muscle insert?

Lesser tubercle of the humerus

What is the action of the subscapularis muscle?

Medially rotate the shoulder and stabilize the head of humerus

Which nerves innervate the subscapularis muscle?

Upper and lower subscapular nerves

What is unique about the subscapularis muscle among the rotator cuff muscles?

It is the only rotator cuff muscle that attaches to the lesser tubercle.

Which rotator cuff muscle(s) abduct?

Supraspinatus

Which rotator cuff muscle(s) adduct?

Infraspinatus, teres minor

Which rotator cuff muscle(s) laterally rotate?

Infraspinatus, teres minor

Which rotator cuff muscle(s) medially rotate?

Subscapularis

What action do all four muscles have in common?

Stabilization of the glenohumeral (shoulder) joint

What is the origin of the Rhomboid Major?

Spinous processes of T2-T5

Where does the Rhomboid Major insert?

Medial border of the scapula between the spine of the scapula and the inferior angle

What is the action of the Rhomboid Major?

Adduct the scapula, elevate the scapula, downwardly rotate the scapula

What nerve innervates the Rhomboid Major?

Dorsal scapular

What is the origin of the Rhomboid Minor?

Spinous processes of C7-T1

Where does the Rhomboid Minor insert?

Upper portion of the medial border of the scapula, across from spine of scapula

What is the action of the Rhomboid Minor?

Adduct the scapula, elevate the scapula, downwardly rotate the scapula

What nerve innervates the Rhomboid Minor?

Dorsal scapular nerve

What is the origin of the Levator Scapula?

Transverse processes of the first through fourth cervical vertebrae

Where does the Levator Scapula insert?

Medial border of the scapula, between the superior angle and the superior portion of the spine of scapula

What is the unilateral action of the Levator Scapula?

Elevate the scapula, downwardly rotate the scapula, laterally flex head and neck, rotate head and neck to the same side

What is the bilateral action of the Levator Scapula?

Extend the head and neck

What nerves innervate the Levator Scapula?

Cervical and dorsal scapular