Lecture 4: Upper limb II: Scapular Muscles and Axilla

Scapular Muscles

deltoid

supraspinatus

infraspinatus

teres minor

teres major

subscapularis

deltoid

Origin- lateral 1/2 of clavicle, acromion, scapular spine

Insertion- deltoid tuberosity

Innervation- axillary

Actions- abduction 15-90 can do everything BUT adduction

supraspinatus

Origin- supraspinous fossa of scapula

Insertion- greater tubercle of humerus

Innervation- suprascapular

Actions-abduction 0-15*

Infraspinatus

Origin- infraspinous fossa of scapula

Insertion-greater tubercle of humerus

Innervation-suprascapular

Actions- lateral rotation, adduction

teres minor

Origin- lateral border of scapula

Insertion-greater tubercle of humerus

Innervation-axillary

Actions-lateral rotation, adduction

teres major

Origin- inferior angle of scapula

Insertion- intertubercular groove of humerus- medial lip

Innervation- lower subscapular

Actions- adduction, medial rotation

Subscapularis

Origin- subscapular fossa

Insertion-greater tubercle of humerus

Innervation-upper and lower subscapular

Actions- medial rotation, adduction

Movement in the Shoulder Joint

Abduction/ adduction

Flexion/ Extension

Medial Rotation/ Lateral Rotation

Circumduction

Joints that movement at Shoulder joint depends on

Glenohumeral joint movement

Sternoclavicular joint movement

Acromioclavicular joint movement

Scapular rotation

Abduction at the Shoulder Joint

pure abduction is limited to 90* by the acromion

Deltoid muscle is only effective in abduction AFTER initiation by the supraspinatus muscle.

Abduction over 90* requires scapular rotation

Lateral Rotation at the Shoulder Joint

tilting of the scapula such that the inferior angle moves away from the vertebral column

Glenoid cavity tilts upwards via serratus anterior and trapezius

Medial Rotation at the Shoulder Joint

tilting of the scapula such that the inferior angle moves towards the vertebral column

Glenoid cavity tilts downward via the rhomboid major and minor, pectoralis minor, levator scapulae and trapezius

Rotator Cuff (SITS muscles)

- no major ligaments

-supported by the tendons of the rotator cuff muscles

major role in stabilizing the head of the humerus during shoulder movements

acts in rotation of the humerus

Tendinous insertions of:

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

Inflammation of the rotator cuff

most often involves the supraspinatus tendon and the overlying subdeltoid bursa; both structures can be compresses in the small spaces between the acromion and the humerus

Shoulder Dislocation

usually occurs in the anterior and inferior direction because the joint capsule is reinforced superiorly, anteriorly and posteriorly by the rotator cuff tendons but NOT Inferiorly.

-can damage the axillary artery and nerve

Upper Limb Muscle Testing

Deltoid: resisted abduction of arm at 90*

Supraspinatus: resisted initial abduction

Infraspinatus and teres minor: resisted lateral rotation

Subscapularis: resisted medial rotation or lift off test

Rotator Cuff (especially supraspinatus): inverted soda can test

Impingement test

AXILLA

Boundaries, Contents, Axillary Artery

Axilla boundaries

Anterior, Posterior, Medial, Lateral

Axilla anterior boundary

Clavicle and pectoral muscles

Axilla posterior boundary

scapula and subscapularis muscle

Axilla medial boundary

Serratus anterior muscle

Axilla lateral boundary

humerus

Axilla Contents

Axillary Artery

Axillary vein

Brachial plexus

Long head of the biceps brachii muscles

Short head of the biceps brachii muscles

Coracobrachialis muscle

Axillary Artery

artery that carries oxygenated blood to the axilla (armpit) area

Axillary vein

accompanying vein of axillary artery,located medial & superficial to axillary artery

Brachial Plexus

network of interlacing nerves found in the upper arm area

Long head of the biceps brachii muscles

origin: supraglenoid tubercle

insertion: radial tuberosity

movement: flexes elbow, supinates forearm, flexes shoulder

Short head of the biceps brachii muscles

origin: coracoid process

insertion: radial tuberosity

movement: flexes elbow, supinates forearm, flexes shoulder

Coracobrachialis muscle

flexion, adduction, horizontal adduction, diagonal adduction

Axillary Artery; break down

divided into 3 parts by the pectoralis minor muscle

extends from the first rib to the inferior margin of teres major muscle

Axillary Artery: part 1

I. proximal to the pectoralis minor muscle

II. superior thoracic artery to the 1st/2nd intercostal spaces (small)

Axillary Artery: part 2

I. distal to the pecoralis minor muscle

II. thoracoacromial trunk with branches to shoulder, acromion, deltoid, clavicle, and pectoralis

III. lateral thoracic artery (highly variable) to breast and lateral chest wall

Axillary Artery: part 3

I. distal to the pectoralis minor muscle

II. anterior humeral circumflex artery (sometimes absent)

III. posterior humeral circumflex artery (usually larger than its anterior partner)

IV. subscapular artery (largest branch of the axillary artery) divides into the thoracodorsal and circumflex scapular arteries.

brachiocephalic trunk

The first large artery arising from the aortic arch. It carries oxygenated blood to the neck, head, and right forelimb.

subclavian artery

Both a left and right, blood vessels that supply blood to the shoulders and upper limbs.

superior thoracic artery

first branch of axillary artery

supplies 1st and 2nd intercostal spaces

thoracoacromial artery

supplies superior shoulder and pectoral regions

subscapular artery

serves scapula and dorsal thorax (upper back muscles)

anterior circumflex humeral artery

Origin: axillary (this is smaller then the one opposite to it)

posterior circumflex humeral artery

Origin: axillary (this is bigger then the one opposite to it)

circumflex scapular artery

Originates as a branch of the subscapular artery, which is a branch of the axillary artery

Leaves the axilla through the triangular space to enter the posterior scapular region

brachial artery

The major vessel in the upper extremity that supplies blood to the arm.

lateral thoracic artery

serves lateral chest wall

internal thoracic artery

branch of subclavian artery; supplies costal and sternum