Lecture 15: Muscles of the Appendicular Skeleton I

I. Muscles Stabilizing and Moving the Shoulder Girdle

A. General characteristics

1. Muscles closely associated with those of the upper arm

2. Insertions

a. All insert on scapulae

b. One (trapezius) also inserts on clavicle

3. Types of scapular movement

a. Elevation

b. Depression

c. Protraction (abduction)

d. Retraction (adduction)

e. Upward rotation

f. Downward rotation

B. Trapezius


a. Characteristics

i. Large triangular muscle of the superficial back

b. Origin

i. Occipital bone

ii. Ligamentum nuchae

iii. Spines of thoracic (1-12) and 7th cervical vertebrae

c. Insertion

i. Clavicle

ii. Scapular spine

iii. Acromion process

d. Function

i. Clavicular portion: raises scapula, clavicle and shoulder

ii. Scapular spine and acromion portion

iia. Middle fibers: retracts (adducts) scapula towards vertebral column

iib. Lower fibers: depresses and pulls scapula downward

e. Synergists

i. Levator scapulae

ii. Rhomboideus

C. Serratus anterior

a. Origin

i. Outer surface of ribs 1-8

b. Insertion

i. Vertebral border of scapula

c. Function

i. Protraction (abduction); upward rotation

D. Pectoralis minor


a. Origin

i. Sternal ends of ribs 2-5

b. Insertion

i. Coracoid process

c. Function

i. Pulls scapula anteriorly


II. Muscles Stabilizing Scapulohumeral Joint and Moving Upper Arm

A. Flexors

1. Pectoralis major


a. Characteristics

i. Large breast muscle over pectoralis minpr

b. Origin

i. Sternal manubrum

ii. Ribs 1-6

iii. Clavicle

c. Insertion

i. Lateral lip of humeral intertubercular groove

d. Function

i. Primary flexor and adductor

ii. Medial rotation

e. Synergists

i. Coracobrachialis

ii. Deltoid


B. Abductors

1. Deltoid (see prior figure)

a. Characterisctics

i. Large, thick, triangular muscle responsible for the roundness of shoulders

b. Origin (same as insertion of trapezius)

i. Clavicle

ii. Scapular spine

iii. Acromion process

c. Insertion

i. Deltoid tuberosity of humerus

d. Function

i. Adduction*

ii. Flexor

iii. Extensor

2. Supraspinatus (C below)

a. Origin

i. Supraspinator fossa of scapula

b. Insertion

i. Greater tubercle of humerus

c. Function

i. Assistant abductor

ii. Superior border of musculotendinous cuff


C. Extensors

1. Latissimus dorsi


a. Characterisctics

i. Wide triangular muscle of the lower back

b. Origin

i. Lower thoracic vertebrae

c. Insertion

i. Floor and medial wall of intertubercular groove of humerus

d. Function

i. Extension (e.g., swimming, rowing, climbing)

2. Teres major (assistant extensor)

a. Origin

i. Scapular lateral border

b. Insertion

i. Medial lip of intertubecular groove of humerus


D. Rotators (B above)

1. Subscapularis

a. Origin

i. Scapular subscapular fossa I (scapula)

b. Insertion

i. Lesser tubercle of humerus

c. Function

i. Chief internal and medial rotator

ii. Anterior border of musculotendinous cuff

2. Infraspinatus

a. Origin

i. Scapular infraspinator fossa

b. Insertion

i. Greater tubercle of humerus

c. Function

i. External or lateral rotator

ii. Upper posterior border of musculotendinous cuff

3. Teres minor

a. Origin

i. Lateral border of scapula

b. Insertion

i. Greater tubercle of humerus

c. Function

i. External or lateral rotator

ii. Lower posterior border of musculotendinous cuff


III. Muscles on Upper Arm and Moving Forearm at Elbow Joint

A. General characteristics

1. Originate on pectoral girdle and humerus

2. Insert on humerus, radius and ulna

3. Compartments

a. Anterior compartment: flexors

b. Posterior compartment: extensors

B. Anterior compartment: flexors

1. Biceps brachii


a. Origin

i. Long head: supraglenoid tubercle

ii. Short head: Scapular coracoid process

b. Insertion

i. Radial tuberosity (radius)

c. Function

i. Chief flexor of the arm at the elbow

2. Brachialis

a. Origin

i. Anterior, lower 2/3 of humerus

b. Insertion

i. Coracoid process of ulna


C. Posterior compartment: extensors

1. Triceps brachii


a. Origin

i. Long head: infraglenoid tubercle of scapula

ii. Lateral head: posterior lateral surface of humerus

iii. Medial head: entire posterior surface of humerus

b. Insertion

i. Ulnar olecranon process

ii. Olecranon bursa

c. Function

i. Chief extensor of arm at elbow joint


IV. Muscles of Forearm

A. General characteristics

1. Muscles originate on distal humerus and proximal radius and ulna

2. Muscles insert on carpals, metacarpals and phalanges

3. Bulk of muscle located in proximal forearm

4. Tendons start in distal forearm

5. Compartments

a. Anterior compartment

i. Flexors

b. Posterior compartment

i. Extensors

6. Tendons are held in place at the wrist by the flexor retinaculum

B. Anterior compartment: organized based on position relative to surface

1. Superficial: flexors at wrist


a. Origin: epicondyle of humerus

b. Insertions

i. Flexor carpi radialis: base of the 2nd metacarpal

ii. Palmaris longus: palm aponeurosis (deep fascia)

iii. Flexor carpi ulnaris: carpals and 5th matacarpal

2. Intermediate: flexor of digits

a. Origin

i. Epicondyle of humerus

ii. Ulnar and radial heads

b. Insertion

i. Flexor digitorum superficialis: middle phalanx, 2nd 5th finger (see B)

3. Deep: flexors of digits


a. Origin

i. Anterior shaft of ulna and radius

b. Insertions

i. Flexor digitorum profundus: distal phalanx, 2nd 5th finger

ii. Flexor pollicis longus: distal phalanx of pollex


C. Posterior compartment (see D)

1. Superficial: extensors of wrist joint and digits

a. Origin: common tendon that attaches to lateral humeral epicondyle

b. Insertions (extensors of wrist joint)

i. Extensor carpi radialis longus: base of 2nd metacarpal

ii. Extensor carpi radialis brevis: base of 3rd metacarpal

iii. Extensor carpi ulnaris: base of 5th metacarpal

c. Insertions (extensors of digits)

i. Extensor digitorum: middle, distal phalanx, 2nd 5th finger

ii. Extensor digitorum minimi: middle, distal phalanx, 5th finger

2. Deep

a. Origin: posterior surface of ulna and radius

b. Insertions

i. Abductor pollicis longus (and brevis): base of 1st metacarpal

ii. Extensor pollicis longus (and brevis): distal (and proximal) phalanx of polis

iii. Extensor indicis: proximal phalanx of index finger


D. Supinator and pronators

1. Supinator: deep, posterior compartment

a. Origin

i. Lateral humeral eipcondyle

ii. Proximal lateral ulna

b. Insertion

i. Proximal lateral radius

2. Pronator teres: anterior compartment, superficial

a. Origin

i. Medial humeral epicondyle

ii. Ulnar coronoid process

b. Insertion

i. Lateral radius

3. Pronator quadratus: intermediate, anterior compartment

a. Origin

i. Anterior, distal ulna

b. Insertion

i. Anterior distal radius


V. Muscles of the Hand (Not responsible for these muscles)

A. Thenar muscles of thumb (4)

1. Abductor pollicis brevis

2. Flexor pollicis brevis

3. Opponens pollicis

4. Abductor pollicis

B. Hypothenar muscles of little finger (3)

1. Abductor digiti minimi

2. Flexor digiti minimi brevis

3. Opponens digiti minimi

C. Midpalmar muscles (3)

1. Lumbricals

2. Palmar interossei

3. Dorsal interossei