[Anatomy] Shoulder

Front 1

extrinsic muscles of the back

Back 1

originate on the posterior aspect of the axial skeleton; trapezius, rhomboid minor and major, levator scapulae, latissimus dorsi,

Front 2

shoulder muscles

Back 2

include extrinsic muscles of the back, muscle of pectoral region, intrinsic muscles of shoulder

Front 3

trapezius

Back 3

Origin: occipital bone, nuchal ligament, cervical and thoracic spinous processes
Insertion: clavicle, acromion, spine of scapula

Action: elevation, retraction, depression, and upward rotation of scapula
Innervation: spinal accessory nerve (CN XI)

Note: the spinal accessory n. (CN XI) can be tested by asking the patient to shrug their shoulders against resistance.

Front 4

rhomboid minor and major

Back 4

Origin: nuchal ligament and cervical spinous processes (minor); thoracic spinous processes (major)
Insertion: medial border of scapula
Action: retraction and downward rotation of scapula (also fixes scapula on body wall)
Innervation: dorsal scapular nerve

Front 5

levator scapulae

Back 5

Origin: cervical transverse processes
Insertion: superior angle of scapula
Action: elevation and downward rotation of scapula
Innervation: dorsal scapular nerve and ventral rami of C3, C4

Front 6

latissimus dorsi

Back 6

Origin: thoracolumbar fascia, iliac crest, ribs
Insertion: proximal humerus
Action: extension and adduction of glenohumeral joint (GHJ), medial rotation of humerus
Innervation: thoracodorsal nerve

Front 7

muscles of pectoral region

Back 7

originate on the anterior aspect of the axial skeleton; pectoralis major and minor, serratus anterior

Front 8

pectoralis major

Back 8

Origin: clavicle, sternum, costal cartilages of superior ribs
Insertion: proximal humerus
Action: adduction, flexion, and medial rotation of GHJ
Innervation: medial and lateral pectoral nerves

Front 9

pectoralis minor

Back 9

Origin: superior ribs
Insertion: coracoid process of scapula
Action: protraction and depression of scapula (stabilizes scapula)
Innervation: medial pectoral nerve

Front 10

serratus anterior

Back 10

Origin: superior ribs
Insertion: medial border of scapula
Action: protraction and upward rotation of scapula, fixes scapula on body wall
Innervation: long thoracic nerve

Note: Lesion of the long thoracic nerve (common due to
superficial location) paralyzes the serratus anterior muscle,
resulting in a winged scapula

Front 11

intrinsic muscles of shoulder

Back 11

originate on the scapula and insert on the humerus; rotator cuff muscles crate a supportive musculotendinous cuff around the glenohumeral joint (stabilizing this joint); SITS

Front 12

supraspinatus

Back 12

Origin: supraspinous fossa of scapula
Insertion: greater tubercle of humerus
Action: abduction of GHJ (initial 15º), stabilize GHJ
Innervation: suprascapular nerve

Front 13

infraspinatus

Back 13

Origin: infraspinous fossa of scapula
Insertion: greater tubercle of humerus
Action: lateral rotation of GHJ, stabilize GHJ
Innervation: suprascapular nerve

Front 14

teres minor

Back 14

Origin: lateral border of scapula
Insertion: greater tubercle of humerus
Action: lateral rotation of GHJ, stabilize GHJ
Innervation: axillary nerve

Front 15

subscapularis

Back 15

Origin: subscapular fossa of scapula
Insertion: lesser tubercle of humerus
Action: medial rotation and adduction of GHJ, stabilize GHJ
Innervation: upper and lower subscapular nerves

Front 16

teres major

Back 16

Origin: inferior angle of scapula
Insertion: proximal humerus
Action: medial rotation and adduction of GHJ
Innervation: lower subscapular nerve

Front 17

deltoid

Back 17

(three-part muscle)
Origin: clavicle, acromion and spine of scapula
Insertion: deltoid tuberosity of humerus
Action:
Anterior portion: flexion and medial rotation of GHJ
Middle portion: abduction of GHJ (after initial 15º)
Posterior portion: extension and lateral rotation of GHJ
Innervation: axillary nerve

Front 18

arterial supply of shoulder

Back 18

subclavian artery gives rise to thyrocervical trunk (Transverse cervical artery and suprascapular artery); axillary artery gives rise to thoracoacromial artery and lateral thoracic artery

Front 19

transverse cervical artery

Back 19

branch of thyrocervical trunk
• Superficial branch supplies trapezius
• Deep branch (= dorsal scapular artery) supplies rhomboids and levator scapulae. This branch may arise separately from the subclavian artery.

Front 20

suprascapular artery

Back 20

branch of thyrocervical trunk
• Supplies supraspinatus and infraspinatus
• Contributes to collateral circulation of the shoulder (see M&A p. 426)
• This Artery courses over the superior transverse scapular ligament while the suprascapular Nerve passes under the superior transverse scapular ligament
• “Army over Navy”

Front 21

thoracoacromial artery

Back 21

branch of axillary artery
• Supplies pectoral muscles and deltoid

Front 22

lateral thoracic artery

Back 22

branch of axillary artery
• Courses with the long thoracic nerve
• Supplies serratus anterior and pectoral muscles

Front 23

venous drainage of shoulder

Back 23

Parallels the arterial supply. Adjacent vessels share the same names (exception: there is no thyrocervical vein). It is not usual for a single artery to have a pair of associated veins.