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PECTORAL REGION

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     Pectoralis major muscle

Origin	Clavicular head: anterior surface of medial half of clavicle Sternocostal head: anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle
Insertion	Lateral lip of intertubercular groove of humerus
Innervation	Medial and lateral pectoral nerves
Artery	Pectoral branch of thoracoacromial artery
Action	Adduction of humerus; medial rotation of humerus; draws scapula anteriorly and inferiorly; flexes humerus (clavicular head); extends humerus from flexed position (sternocostal head)

     Pectoralis minor muscle

Origin	Anterior surfaces and superior borders of ribs 3-5; deep fascia that lies over related intercostal spaces
Insertion	Coracoid process of scapula
Innervation	Medial pectoral nerve
Artery	Pectoral branch of thoracoacromial artery
Action	Draws scapula inferiorly and anteriorly to stabilize it

     Subclavius muscle

Origin	Junction of first rib and its costal cartilage
Insertion	Inferior surface of middle third of clavicle
Innervation	Nerve to subclavius
Artery	Clavicular branch of thoracoacromial artery
Action	Anchors and depresses clavicle

     Serratus anterior muscle

Origin	Lateral surfaces of ribs 1-8 and deep fascia overlying the related intercostal spaces
Insertion	Costal surface of medial border of scapula
Innervation	Long thoracic nerve
Artery	Lateral thoracic artery
Action	Protraction and rotation of scapula; keeps medial border and inferior angle of scapula opposed to thoracic wall

EXTRINSIC SHOULDER MUSCLES

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     Trapezius muscle

Origin	Superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of CVII to TXII
Insertion	Lateral one-third of clavicle, acromion, spine of scapula
Innervation	Motor-accessory nerve [XI]; proprioception-C3 and C4
Artery	Transverse cervical artery, dorsal scapular artery
Action	Assists in rotating the scapula during abduction of humerus above horizontal; upper fibers elevate, middle fibers adduct, and lower fibers depress scapula

     Latissimus dorsi muscle

Origin	Spinous processes of T7-T12 and related interspinous ligaments; thoracolumbar fascia; and iliac crest; ribs 9-12
Insertion	Floor of intertubercular groove of humerus
Innervation	Thoracodorsal nerve
Artery	Thoracodorsal artery
Action	Adducts, extends, and medially rotates humerus; raises body toward arms during climbing

     Levator scapulae muscle

Origin	Transverse processes of CI to CIV
Insertion	Upper portion medial border of scapula
Innervation	C3 to C4 and dorsal scapular nerve
Artery	Dorsal scapular artery
Action	Elevates scapula

     Rhomboid minor muscle

Origin	Lower portion of ligamentum nuchae, spinous processes of CVII and TI
Insertion	Medial border of scapula at the spine of scapula
Innervation	Dorsal scapular nerve
Artery	Dorsal scapular artery
Action	Retracts (adducts) and elevates scapula

     Rhomboid major muscle

Origin	Spinous processes of TII to TV
Insertion	Medial border of scapula between spine and inferior angle
Innervation	Dorsal scapular nerve
Artery	Dorsal scapular artery
Action	Retracts (adducts) and elevates scapula

INTRINSIC SHOULDER MUSCLES

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     Deltoid muscle

Origin	Lateral third of clavicle, acromion, and spine of scapula
Insertion	Deltoid tuberosity of humerus
Innervation	Axillary nerve
Artery	Deltoid branch of thoracoacromial artery, posterior humeral circumflex artery
Action	Abducts, adducts, flexes, extends, and rotates arm medially and laterally

 

     Supraspinatus muscle

Origin	Supraspinous fossa of the scapula
Insertion	Most superior facet on the greater tubercle of the humerus
Innervation	Suprascapular nerve
Artery	Suprascapular artery
Action	Rotator cuff muscle; initiation of abduction of arm to 15° at glenohumeral joint

     Infraspinatus muscle

Origin	Infraspinous fossa of the scapula
Insertion	Middle facet on posterior surface of the greater tubercle of the humerus
Innervation	Suprascapular nerve
Artery	Suprascapular artery, circumflex scapular artery
Action	Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint

     Teres minor muscle

Origin	Middle part of lateral border of scapula
Insertion	Inferior facet on the posterior surface of the greater tubercle of the humerus
Innervation	Axillary nerve
Artery	Circumflex scapular artery, subscapular artery
Action	Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint

     Teres major muscle

Origin	Posterior surface of inferior angle of scapula
Insertion	Medial lip of the intertubercular sulcus on the anterior surface of the humerus
Innervation	Lower subscapular nerve
Artery	Circumflex scapular artery, subscapular artery
Action	Adduction and medial rotation of arm

     Subscapularis muscle

Origin	Medial two-thirds of subscapular fossa
Insertion	Lesser tubercle of humerus
Innervation	Upper and lower subscapular nerves
Artery	Subscapular artery
Action	Rotator cuff muscle; medial rotation of the arm at the glenohumeral joint

Overview

• (Right side of body) Heart → aorta → brachiocephalic trunk → right subclavian artery
• (Left side of body) Heart → aorta →left subclavian artery
• Subclavian artery becomes the axillary artery after it crosses the first rib
• Axillary artery is divided into three parts.
  • Each part has the same number of branches (i.e., part 1 has 1 branch, part 2 has 2 branches, part 3 has 3 branches) (see chart below)
    • Note: Besides coming directly off of the subclavian artery, the dorsal scapular artery can also come off of the transverse cervical artery. When this happens, it is called the deep branch of transverse cervical artery.
• Axillary artery becomes brachial artery after the inferior border of teres major muscle

Subclavian Artery, Axillary Artery, and Branches

Axillary Artery

Nerves

Important Spaces in Posterior Scapular Region

1. Triangular space
   1. Borders
      1. Teres major
      2. Triceps brachii (long head)
      3. Teres minor
   2. Contents
      1. Circumflex scapular artery
2. Quadrangular space
   1. Borders
      1. Teres major
      2. Humerus
      3. Teres minor
      4. Triceps brachii (long head)
   2. Contents
      1. Axillary nerve
      2. Posterior humeral circumflex artery
3. Triangular interval
   1. Borders
      1. Teres major
      2. Triceps brachii (long head)
      3. Humerus
   2. Contents
      1. Profunda brachii artery
      2. Radial nerve