Muscles of the pectoral girdle

What muscles make up the anterior axio-appendicular region?

-pectoralis major

-pectoralis minor

-subclavius

-serratus anterior

Pectoralis major: general action and innervation

A: humeral ADD and IR

N: medial and lateral pectoral nerves

Pectoralis major upper fibers: action and innervation

A: shoulder flexion and internal rotation

I: lateral pectoral nerve; C5, C6, C7

Pectoralis major lower fibers: action and innervation

A: shoulder extension (from already flexed position)

I: medial and lateral pectoral nerves; C6-8, T1

Pectoralis minor: action and innervation

A:

• fixed origin: tilt scapula anteriorly

• fixed insertion: elevate ribs to assist inhalation

N: medial pectoral nerve; C7, C8

What can cause thoracic outlet syndrome or radiating nerve symptoms down the upper extremity?

Overcontraction of the pectoralis minor.

(Causes impingement on cords of brachial plexus and axillary blood vessels as they travel b/w coracoid process and rib cage)

Subclavius: action and innervation

A: anchor and depress clavicle

N: nerve to subclavius; C5, C6

Serratus anterior: action and innervation

A: scapular protraction, upward rotation of scap, and contracts to hold medial border of scap firmly against the rib cage

N: long thoracic nerve; C5-7

What makes up the anterior axillary fold?

inferior angle of pec major

What are the superficial muscles of posterior axio-appendicular?

- trapezius

- latissimus dorsi

Trapezius: action and innervation

A:

• fixed origin: elevation (upper fibers) and depression (lower fibers). retraction (mostly mid fibers), upward rotation of glenoid cavity (upper and lower fibers)

• fixed insertion: extension, lateral flexion, contralateral rotation of head and cervical spine

N: spinal accessory nerve: C3, C4

Latissimus dorsi: origin + insertion

O:

• spinous processes of T6-T12, thoracolumbar fascia, lumbosacral fascia, posterior lip of of iliac crest, ribs 8-12

I:

• floor of intertubercular sulcus on humerus

Latissimus dorsi: action and innervation

A: shoulder adduction, IR, and EXT; Also depress scap and laterally flex trunk

N: thoracodorsal nerve; C6-8

What makes up the posterior axillary fold?

Teres major

What are the deep muscles of the posterior axio-appendicular region?

-levator scapulae

-rhomboid minor

-rhomboid major

levator scapulae: origin + insertion

O:

• posterior tubercles of transverse processes of C1-C4

I:

• medial border of scapula between superior angle and root of scapula

Levator scapulae: action and innervation

A:

• fixed origin: elevation and downward rotation of scap

• fixed insertion unilateral: lateral flexion, ipsilateral rotation of C/S

• fixed insertion bilateral: extension of C/S

N: dorsal scapular nerve; C5

rhomboid major origin + insertion

O:

• spinous processes of T2-T5 vertebrae

I:

• medial border of scapula between scapular spine and inferior angle

rhomboid major: action and innervation

A: scapular retraction, elevation, and downward rotation

N: dorsal scapular nerve; C5

rhomboid minor origin + insertion

O:

• nuchal ligament

• spinous processes of C7,T1 vertebrae

I:

• medial border at root of scapular spine

rhomboid minor: action and innervation

A: scapular retraction and downward rotation

N: dorsal scapular nerve; C5

what muscles make up the scapulo-humeral region?

-deltoid

-teres major

-supraspinatus

-infraspinatus

-teres minor

-subscapularis

deltoid: action and innervation

A: all fibers are active during shoulder abduction

• anterior fibers: shoulder flexion and IR

• middle fibers: shoulder abduction

• posterior fibers: shoulder extension, ER

N: axillary nerve; C5, C6

deloid origin + insertion

O:

• anterior fibers: anterior border, superior surface, lateral 1/3 of clavicle

• middle fibers: lateral margin and superior surface of acromion of scapula

• posterior fibers: inferior lip of posterior border of spine of scapula

I:

• all fibers insert onto deltoid tuberosity of humerus

teres major origin + insertion

O:

• dorsal surface of inferior angle and lower 1/3 of lateral border of scapula

I:

• crest of lesser tubercle of humerus

teres major: action and innervation

A: glenohumeral adduction, IR, and EXT

N: lower subscapular nerve; C5, C6

Acronym for rotator cuff muscles

SITS

• supraspinatus

• infraspinatus

• teres minor

• subscapularis

supraspinatus origin + insertion

O:

• medial 2/3 of supraspinatus fossa on the scapula

I:

• superior facet of greater tubercle of humerus and shoulder capsule

Supraspinatus: action and innervation

A: initiates 1st 15 degrees of shoulder ABD; stabilizes head of humerus

N: suprascapular nerve; C5

infraspinatus origin + insertion

O:

• medial 2/3 of infraspinous fossa of scapula

I:

• middle facet of greater tubercle of humerus and shoulder joint capsule

Infraspinatus: action and innervation

A: glenohumeral ER and stabilizes head of humerus

N: suprascapular nerve; C5, C6

teres minor origin + insertion

O:

• upper 2/3 dorsal surface of lateral border of scapula

I:

• inferior facet of greater tubercle on humerus and shoulder joint capsule

Teres minor: action and innervation

A: glenohumeral ER and stabilizes head of humerus

N: axillary nerve C5, C6

subscapularis origin + insertion

O:

• subcapular fossa of scapula

I:

• lesser tubercle of humerus and shoulder joint capsule

Subscapularis: action and innervation

A: glenohumeral IR and stabilizes head of humerus

N: upper and lower subscapular nerves; C5, C6

what tendon is usually torn in a rotator cuff tear? what population is this most common in?

supraspinatus tendon; older adults

pec major origin + insertion

O:

• upper fibers - anterior surface of medial 1/3 of clavicle

• lower fibers - anterior surface of sternum, superior 6 costal cartilages and aponeurosis of external abdominal oblique

I:

• crest of greater tubercle

• upper fibers are more anterior and caudal

• lower fibers twist on themselves + more posterior and cranial

pec minor origin + insertion

O:

• superior margin, outer surface of ribs 3-5

I:

• medial border and superior surface of coracoid process on scapula

subclavius origin + insertion

O:

• junction of 1st rib and its costal cartilage

I:

• inferior surface of middle 1/3 of clavicle

serratus anterior origin + insertion

O:

• outer surfaces and superior borders of ribs 1-8

I:

• costal surface of the medial border of scapula

trapezius origin + insertion

O:

• upper fibers: external occipital protuberance, spinal processes of C1-C7 vertebrae

• middle fibers: spinous processes of T1-T5 vertebrae

• lower fibers: spinous proesses of T6-T12 vertebrae

I:

• upper fibers: lateral 1/3 of clavicle and acromion process of scapula

• middle fibers: medial margin of acromion and superior lip of spine of scapula

• lower fibers: tubercle at root of spine of scapula