THE SHOULDER THE SHOULDER GIRDLEGIRDLE

Maribel G. Castro-Enano, M.D.Maribel G. Castro-Enano, M.D.

CPU College of MedicineCPU College of Medicine

Introduction1. Man phylogenetically follows the development of the

vertebrate species.

2. Pinching, holding and grasping are the 3 basic motor functions of the hand.

3. The hand has a rich sensory innervation and is thus the organ of feeling.

4. In relation to the telencephalon, the hand is also an organ of expression. Other animals cannot do this.

5. Greek/Latin terms:arm – brachium

elbow – cubitus

forearm - antibrachium

wrist - carpus

hand - manus

A. Skeletal System

1. Clavicle- a long bone, clavius (“little key”)- strut bone – gives a good range of motion to the shoulder- first bone to ossify - the only bony connection of the upper extremity to the axial skeleton- attachment of muscles- transmits force from upper extremity to the axial skeleton

- one of the most commonly fractured bones

2. Scapula- a flat bone with 2 surfaces, a coastal (anterior) and a dorsal (posterior)- triangular in shape with 3 borders (superior, lateral and vertebral) and 3 angles (superior, inferior and lateral)- the lateral angle is the glenohumeral joint- superior angle = T2, inferior angle = T7- in the superior border is the suprascapular notch through which some vessels pass through- has 2 processes the coracoid and the spine (T3)- the spine of the scapula divides it into a smaller supraspinatus & a larger infraspinatus fossa; the 2 fossae communicate with each other at the spinoglenoid notch

2. Scapula cont….

- free border or crest of the spine ends superior to the shoulder joint in a free, flattened expanded piece of bone, the acromion

- the acromion articulates with the clavicle

- on the lateral angle is a round-shaped shallow facet, the glenoid

- the glenoid articulated with the head of the humerus , the glenohumeral joint

3. Humerus

- glenohumeral joint – where most of the movements of the shoulder will occur

a. head – covered with cartilage, directed superomedially

b. anatomical neck – fibrous capsule of the joint is attached

c. lesser tubercle – points anteriorly, insertion for the subscapularis

d. greater tubercle – bulges laterally beyond the acromion; gives the shoulder its roundness; insertion for the supraspinatus, infraspinatus & teres minor

e. surgical neck – between the head and the tubercles proximally and the body distally; completely encircled by the circumflex humeral

vessels and partly by the axillary nerve

3. Humerus cont…..

- between the greater and the lesser tubercles is the bicipital groove (intertubercular groove) where the tendon of the biceps attach

- the deltoid tuberosity in the shaft is the attachment of the deltoid m.

- above the deltoid tuberosity is the spiral groove where the radial nerve will course through

- into the crest of the greater tubercle the pectoralis major is inserted

- into the crest of the lesser tubercle the teres major is inserted

The HumerusThe Humerus

Bones of the Shoulder Girdle

B. Joints/Articulations1. Sternoclavicular Joint

- ligaments keep the joint stablea. thick articular disc of fibrocartilage between the joint prevents the clavicle from being displaced mediallyb. anterior and posterior sternoclavicular ligamentsc. costoclavicular ligament – ligament from the first rib to the clavicled. interclavicular ligament – ligament between calvicles; homologous to the “wishbone”e. coracoclavicular ligament – between the coracoid process and the clavicle; is in 2 parts: a conoid & a trapezoid

1.) prevents the scapula from being driven medially2.) it is the mainstay of the acromioclavicular joint and, so long

as it is intact, the joint may , indeed, undergo subluxation, but the acromion cannot be driven inferior to the clavicle

3.) suspends the scapula

1. Sternoclavicular Joint cont….

f. coracoacromial ligament – between the coracoid process and acromion

g. coracohumeral ligament – between the coracoid process and the humerus

2. Acromioclavicular Joint

- a synovial joint

- strong parallel fibers form a complete capsule and a small articular disc hangs into the cavity

1.) prevents the scapula to move vertically on the chest wall when the pectoral girdle rises and falls

2.) permits the scapula (with the glenoid cavity) to glide forward and backward on the clavicle and so to face directions convenient to eh head of the humerus

3.) its freedom is essential to free elevation of the limb

- vulnerable to injury in contact sports

3. Glenohumeral Joint

- stabilized by muscles and a glenohumeral ligament

4. Scapulothoracic Articulation

- actually not a joint

- scapula is not attached to the thoracic wall but can glide and move

C. Muscular System

1. The Pectoralis Muscles – pectus (chest)

a. pectoralis major

- covers almost the entire chest

- origin : it has 2 heads:

1.) clavicular – from the clavicle

2.) sternocostal – from the sternum and ribs

insertion : inserted by means of a folded aponeurosis into the crest of the greater tubercle of the humerus (lateral lip of the bicipital groove)

- action : adducts the humerus and rotates it medially

2. The Superficial Extrinsic Back Muscles

a. trapezius

- origin: skull and spinous processes of the cervical vertebrae via the ligamentum nuchae and all 12 thoracic spines

- insertion: lateral 3rd of the clavicle, acromion and crest of the spine of the scapula, and tubercle on the inferior lip of the crest of the spine

- action: suspensory muscles of the shoulder girdles; square the shoulders and elevate the shoulder girdle

b. pectoralis minor

- origin: ribs (3rd, 4th 5th )

- insertion: coracoid process

- action: stabilizes scapula in the thoracic cage

c. subclavius

- origin: rib 1

- insertion: inferior surface of middle 3rd of clavicle

- action: draws scapula medially

d. serratus anterior

- origin: outer surfaces of the the first 8 ribs

- insertion: medial border of scapula

- action: protract the scapula anteriorly

- “winged scapula” – results from paralysis of the serratus anterior

2. The Back Muscles cont….

b. latissimus dorsi

- widest muscle of the back

- origin: by an aponeurosis (thoracolumbar fascia), from the inferior 6 thoracic, all lumbar and sacral spines, & the outer lip of the iliac crest, also arises from ribs 9-12

- insertion: lesser tubercle of the humerus and medial lip of the intertubercular sulcus

- action: extends, medially rotates and adducts the humerus; brings the outstretched arm from above the head to behind the back

3. The Deep Extrinsic Back Muscles

a. levator scapulae

- origin: transverse processes of the cervical vertebrae 1-4

- insertion: superior angle of scapula

- action: elevates the scapula

b. rhomboideus (minor and major)

- origin: ligamentum nuchae and the spines of cervical and 1st 4 thoracic vertebrae

- insertion: medial border of scapula

- action: retracts/depresses the shoulder

4. The Intrinsic Muscles

a. deltoideus

- origin: lateral 3rd of the clavicle, the lateral border of the acromion, and the whole length of the spine of the scapula

- insertion: deltoid tuberosity

- action: abducts, flexes and extends the shoulder

b. supraspinatus

- origin: supraspinatus fossa

- insertion: greater tubercle

- action: with the deltoid elevate the arm

4. The Intrinsic Muscle cont…..

c. infraspinatus

- origin: infraspinatus fossa

- insertion: greater tubercle

- action: depress the arm

d. teres minor

- origin: lateral border of the scapula

- insertion: greater tubercle

- action: lateral rotation of the humerus

e. subscapularis

- origin: subscapular fossa (anterior surface of scapula)

- insertion: lesser tubercle

- action: medial rotation & adduction of the humerus

4. The Intrinsic Muscles cont…..

f. teres major

- origin: dorsum of the inferior angle of the scapula

- insertion: crest of the lesser tubercle tubercle anteriorly

- action: adducts and medially rotates arm

Rotator Cuff Muscles

(supraspinatus, infraspinatus, teres minor, subscapularis)

- they form a musculotendinous rotator cuff for the shoulder joint

- a mass of tendons fused with the lateral part of the capsule of the shoulder joint

- all except supraspintus are rotators of the humerus

- Protects the shoulder joint and gives it stability by holding the head of the glenoid cavity of the scapula

D. Bursae Associated with the Shoulder Joint

- Lined by synovial fluid- Lessens friction between a muscle and a

bone, or sometimes between the skin and a bony prominence

1. Subscapularis Bursa

- lies between the subscapularis tendon and the neck of the scapula

- protects the subscapularis tendon where it passes inferior to the root of the coracoid process and over the neck of the scapula

- usually communicates with the cavity of the shoulder joint through an opening in its fibrous capsule

2. Subacromial Bursa

- lies between the deltoid muscle, supraspinatus tendon, & the fibrous capsule of the shoulder joint

- does not normally communicate with the cavity of the shoulder

- facilitates movement of the deltoid muscle over the fibrous capsule of the shoulder joint and the supraspinatus tendon

E. The Axilla

- has 4 walls (anterior, posterior, medial, lateral)

- Anterior wall: pectoralis major (pectoralis minor and subclavius)

- Posterior wall: subscapularis, teres major, and latissimus dorsi

- Lateral wall: the intertubercular sulcus

- Medial wall: intercostal muscles covered with serratus anterior

F. The Brachial Plexus

- A plexus is a network of nerves

- Arise from the ventral rami of C5-8, T1a. sensory nerves go to the dorsal root and motor nerves go to the ventral root

b. the venral rami is a mixed nerve ( sensory and motor)

c. the dorsal rami provide for some of the deep muscles of the back

F. The Brachial PlexusF. The Brachial Plexus

G. The Vascular SystemG. The Vascular System- great axillary vessels (and nerves)

- enveloped in the axillary sheath which is continuous with the prevertebral fascia of the neck

- enter the axilla at its apex through the triangle formed by the clavicle, 1st rib and superior border of the scapula

- Great Arterial Trunk of the limb

- called the subclavian artery until it reaches the inferior border of the 1st rib

*Sources of Blood Supply to the Scapular Area from the Subclavian A.

1. suprascapular artery

2. transverse cervical a.

- in the axilla, it is known as the axillary artery

- in the arm, it becomes the brachial artery

A. The Axillary Artery

- divided into 3 parts by the pectoralis minor

Branches per Region:

1. supreme thoracic artery

2. thoracoacromial a. – large branch which sends 1 branch each to the thorax, deltoid and acromion

lateral thoracic a. – accompanies the long thoracic n.

3. anterior humeral circumflex a.

posterior humeral circumflex a. – goes around the surgical neck of the humerus; accompanies the axillary n.

subscapular a. – follows the inferior border of the pectoralis minor; source of collateral circulation in case the axillary artery becomes occluded

- sends a large branch to the dorsum of the scapula, the circumflex scapular artery

2. The Axillary Vein

- lies on the medial or concave side of its artery

- continuation of the basilic vein

- at the 1st rib becomes the subclavian vein

- receives tributaries corresponding to the 6 branches of the axillary artery

- receives the 2 venae comitantes of the brachial artery and the cepahalic vein

3. The Axillary Lymph Nodes

- “checkpoints” which prevent the spread of infection

- arranged in several main groups

a. lateral nodes – receive lymph vessels that ascend along the medial side of the arm and they empty into the

b. apical (infraclavicular) nodes – all the vessels of the limb drain either directly or indirectly into this group, and it in turn drains into the subclavian lymph trunk, which ends in the right lymph duct or (on the left) the thoracic duct

c. pectoral (anterior) nodes - lie along the inf. border of the pectoralis minor with the lateral thoracic vein

d. subscapular (posterior) nodes – lie along the subscapular veins

e. central nodes – lie between the layers of the fascia at the base of the axilly or in the fat deep to it

f. deltopectoral nodes – occasional; small nodes along the cephalic vein

The Axillary Lymph NodesThe Axillary Lymph Nodes

Thank You!Thank You!