Muscles of the shoulder and arm

Question 1

trapezius

Answer 1

O: medial third of superior nuchal line of occipital bone, external occipital protuberance, ligamentum nuchae, spinous processes and supraspinous ligaments of 7th cervical vertebra C7 and all thoracic vertebrae (T1-L2)

I: superior edge of crest of spine of scapula, medial border of acromion, posterior border of lateral 1/3 of clavicle

A: powerful elevator of scapula, rotates scapula during abduction of humerus above horizontal, middle fibers retract scapula, lower fibers depress scapula, particularly against resistance as when using hands to get up from a chair

Question 2

levator scapulae

Answer 2

O: transverse processes of C1 and C2 and posterior tubercles of transverse processes of third and fourth cervical vertebrae C3,4)

I: posterior surface of medial border of scapula from superior angle to root of spine of scapula

A: elevates scapula helps retract scapula helps side flex neck

Question 3

Rhomboid minor

Answer 3

Minor

O: spinous processes of C7 and T1 lower part of ligamentum nuchae

I: posterior surface of medial border of scapula at the root of spine of scapula

A: elevates and retracts scapula

Question 4

rhomboid major

Answer 4

O: spinous processes of T2-5 and intervening supraspinous ligaments

I: posterior surface of medial border of scapula from the root of spine of scapula to inferior angle

A: elevates and retracts scapula

Question 5

serratus anterior

Answer 5

O: lateral surfaces of upper 8 or 9 ribs and deep fascia covering the related intercostal spaces

I: anterior surface of medial border of scapula

A: rotates scapula for abduction and flexion of arm, protracts scapula (pulls it forward on the ribs and holds it closely into the chest wall) facilitating pushing movements such as press-ups or punching

Question 6

Pectoralis major clavicular head

Answer 6

Clavicular head:

O: anterior surface of medial half of clavicle

I: lateral lip of intertubercular sulcus of humerus

A: flexion of extended arm, flexion adduction and medial rotation of arm at glenohumeral joint

Question 7

pectoralis major sternocostal head

Answer 7

O: anterior surface of sternum first seven costal cartilages sternal end of sixth rib aponeurosis of external oblique

I: lateral lip of intertubercular sulcus of humerus

A: extension of flexed arm, flexion, adduction, and medial rotation of arm at glenohumeral joint

Question 8

Latissimus Dorsi

Answer 8

O: spinous processes of lower six thoracic vertebrae and related interspinous ligaments; via thoracolumbar fascia (a broad sheet of tendon) to the spinous processes of lumbar vertebrae related interspinous ligaments, and iliac crest lower three or four ribs

I: twists to insert into the floor of intertubercular sulcus of humerus just below the shoulder joint

A: adduction, medial rotation, and extension of the arm at the glenohumeral joint, it is one of the chief climbing muscles since it pulls shoulders downward and backward and pulls trunk up to fixed arms. Assists in forced inspiration by raising lower ribs

Question 9

Deltoid (3 origins) of anterior middle and posterior fibers

Answer 9

O: Anterior fibers: anterior border of lateral one-third of clavicle

O: middle fibers: lateral margin of acromion process

O: Posterior fibers: inferior edge of crest of spine of scapula

I: deltoid tuberosity of humerus

A: major abductor of arm (abducts beyond initial 15 degrees which is done by supraspinatus) anterior fibers assist in flexing the arm; posterior fibers assist in extending the arm

Question 10

supraspinatus

Answer 10

O: medial two thirds of supraspinous fossa of scapula and deep fascia that covers the muscle

I: most superior facet on the greater tubercle of humerus

A: initiates abduction of arm to 15 degrees at glenohumeral joint (at which point deltoid takes over)

Question 11

infraspinatus

Answer 11

O: medial 2/3 of infraspinous fossa of scapula and deep fascia that covers the muscle

I: middle facet on the posterior surface of greater tubercle of humerus

A: lateral rotation of arm at glenohumeral joint

Question 12

Teres minor

Answer 12

O: upper 2/3 of a strip of bone on posterior surface of scapula immediately adjacent to lateral border of scapula

I: inferior facet on greater tubercle of humerus

A: lateral rotation of arm at glenohumeral joint

Question 13

subscapularis

Answer 13

O: medial 2/3 of subscapular fossa

I: lesser tubercle of humerus

A: medial rotation of arm at glenohumeral joint

Question 14

Teres major

Answer 14

O: oval area on lower third of posterior surface of inferior angle of scapula

I: medial lip of intertubercular sulcus on anterior surface of humerus

A: medial rotation and extension of arm at glenohumeral joint

Question 15

Biceps Brachii long and short head (2 origins)

Answer 15

O: Long Head: supraglenoid tubercle of scapula

O: Short head: tip of coracoid process

I: radial tuberosity

A: powerful flexor of forearm at elbow joint. Supinates forearm accessory flexor of arm at glenohumeral joint (been described as the muscle that puts the corkscrew and pulls out the cork)

Question 16

brachialis

Answer 16

O: anterior aspect of humerus (medial and lateral surfaces and adjacent intermuscular septae

I: tuberosity of ulna

A: powerful flexor of the forearm at elbow joint

Question 17

Triceps Brachii 3 origins long medial and lateral head

Answer 17

O: Long Head: infraglenoid tubercle of scapula

O: Medial head: posterior surface of humerus (below and medial to radial groove)

O: lateral head: posterior surface of humerus (above and lateral to radial groove)

I: posterior part of olecranon process of ulna

A: extends forearm at elbow joint, long head can also extend and adduct arm at shoulder joint