Shoulder, Arm And Forearm

Front 1

Trapezius

origin: skull and thoracic vertebrae
insertion: clavicle and scapula
shape: trapezium - divided into 3 sections (a) descending convergent fibres, superior; (b) transverse fibres, middle; (c) ascending convergent fibres, inferior
Layer: most superior layer of shoulder region

Group: superficial posterior (shoulder) group

Function:
1) descending part (superior) - elevate scapula
2) middle part - retracts scapula (pull posteriorly)
3) Ascending part (inferior) - descend scapula
4) ascending + descending = rotate glenoid cavity posteriorly

Back 1

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Front 2

Rhomboid minor

origin: cervical and thoracic vertebrae
insertion: medial border of scapula
shape: flat, rhomboid; descending parallel fibres
layer: superior to rhomboid major, under trapezius

Group: superficial posterior (shoulder) group
Function: retract scapula, rotate/depress glenoid cavity fix scapula to thoracic wall

Back 2

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Front 3

Rhomboideus Major

origin: cervical and thoracic vertebrae
insertion: medial border of scapula
shape: flat, rhomboid; descending parallel fibres

Group: superficial posterior (shoulder) group
position: inferior to rhomboid minor, under trapezius

Function: retract scapula, rotate/depress glenoid cavity fix scapula to thoracic wall

Back 3

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Front 4

Levator Scapulae

origin: cervical vertebrae
insertion: superior scapula

group: superficial posterior (shoulder) group
innervation:
position: next to subscapularis, under trapezius

joint:
function: + descending parts of trapezius = elevate scapula/fix against thoracic wall
extend neck (bilaterally with trapezius)
contribute to lateral flexion of neck (unilateral contraction)

Back 4

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Front 5

Latissimus Dorsi

origin: lumbar and thoracic vertebrae
insertion: anterior proximal humerus

group: superficial posterior group
innervation:
position: most superficial lower back muscle

Function: extends, retracts and rotates the humerus medially (directly at glenohumeral joint; indirectly at pectoral girdle - clavicle, scapula, scapulothoracic joint)

Back 5

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Front 6

Teres Major

origin: inferior angle of scapula (posterior surface)
insertion: anterior proximal humerus

group: superficial posterior (shoulder) group
innervation: Axillary nerve
blood supply:
drain into:
position: inferior to teres minor and infraspinatus, under or lateral to trapezius

Function: adducts and medially rotates the arm, important stabilizer of humerus head in glenoid cavity

Back 6

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Front 7

Teres Minor

origin: laterial border of scapula
insertion: greater tubercle of humerus

group: deep rotator cuff group; posterior
innervation: axillary nerve
blood supply:
drain into:
position: superior to teres major, under trapezius and superficial to infraspinatus

joint: glenohumeral joint
function:
1) dynamic ligament: keep head of humerus in socket and stabilize joint throughout wide range of movement
2) rotate humerus: lateral rotation (infraspinatus + teres minor)

Back 7

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Front 8

Supraspinatus

origin: supraspinous fossa of scapula
insertion: greater tubercle of humerus

group: deep rotator cuff group
innervation:
position: above the spine of of scapula (as named), under trapezius (but both anterior and posterior)

Function:
1) Dynamic ligament: keep head of humerus in socket and stabilize joint throughout wide range of movement
2) Assist abduction (away from midline)

Back 8

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Front 9

Subscapularis

origin: subscapular fossa of scapula
insertion: lesser tubercle of humerus

group: deep rotator cuff group
innervation:
position: anterior; under rhomboid minor and pectoralis major

Function:
1) Dynamic ligament - keep head of humerus in socket and stabilize joint throughout wide range of movement
2) rotate humerus - medial rotation (glenohumeral joint)

Back 9

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Front 10

Infraspinatus

origin: infraspinous fossa of scapula
insertion: greater tubercle of humerus

group: deep rotator cuff group; posterior
innervation:
position: posterior below spine of scapula, below teres minor, superior to teres major

Function:
1) Dynamic ligament - keep head of humerus in socket and stabilize joint throughout wide range of movement
2) rotate humerus - lateral rotation (infraspinatus + teres minor; glenohumeral joint)

Back 10

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Front 11

Deltoid

origin: lateral clavicles, acromion, spine of scapula
insertion: proximal, lateral humerus (deltoid tuberosity of humerus)

group: anterior and lateral group
innervation: Axillary nerve
blood supply:
drain into:
position: most superficial proximal humerus and shoulder region; divided in three sections - clavicular (anterior; superior, next to pectoralis major), acromial (middle) and spinal (posterior, on top of infraspinatus) part. Cephalic vein in deltopectoral groove

Function:
1) anterior (clavicular): flexes and medially rotates arm (glenohumeral joint)
2) middle ( acromial): abducts arm (away from midline)
3) posterior (spinal): extends and laterally rotates arm

Back 11

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Front 12

Pectoralis Major

origin: sternum, rib cartilages, clavicle
insertion: greater tubercle of humerus

Group: superficial anterior and lateral group
innervation:
blood supply:
drain into:
position: most superficial anterior muscle, inferior to clavicle and deltoid muscle. Cephalic vein in deltopectoral groove.

function: adducts and medially rotates humerus, draws scapula anteriorly and inferiorly

Back 12

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Front 13

Coracobrachialis

origin: coracoid process of scapula
insertion: medial margins of the humerus shaft

group: flexor (anterior) arm group
innervation: musculocutaneous nerve
blood supply: brachial artery
drain into:
position: under biceps brachii, exposed at medial humerus close to armpit region

Function: flex and adduct arm (glenohumeral joint), stabilise glenohumeral joint (shunt muscle)

Back 13

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Front 14

Triceps Brachii (lateral head, long head, medial head)

origin:
insertion:

group: extensor arm
innervation: radial nerve
blood supply: deep brachial artery
drain into:
location:

Function:

Back 14

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Front 15

Supinator

origin:
insertion:

group: deep extensor (posteriolateral) forearm
innervation: radial nerve
blood supply:
drain into:
location:

Function:

Back 15

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