Muscles of the Pectoral Girdle and Upper Limbs

Layci Harrison

14 Muscles of the Pectoral Girdle and Upper Limbs

Learning Objectives

By the end of this section, you will be able to:

Identify the muscles of the pectoral girdle and upper limbs
Identify the movement and function of the pectoral girdle and upper limbs

Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the pectoral girdle, muscles that move the arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers. The pectoral girdle, or shoulder girdle, consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions.

Muscles That Position the Pectoral Girdle

Muscles that position the pectoral girdle are located either on the anterior thorax or on the posterior thorax (Figure 1 and Table 8). The anterior muscles include the subclavius, pectoralis minor, and serratus anterior. The posterior muscles include the trapezius, rhomboid major, and rhomboid minor. When the rhomboids are contracted, your scapula moves medially, which can pull the shoulder and upper limb posteriorly.

The left panel shows the anterior lateral view of the pectoral girdle muscle, and the right panel shows the posterior view of the pectoral girdle muscle.

Muscles that Position the Pectoral Girdle (Table 8)
Position in the thorax	Movement	Target	Target motion direction	Prime mover	Origin	Insertion
Anterior thorax	Stabilizes clavicle during movement by depressing it	Clavicle	Depression	Subclavius	First rib	Inferior surface of clavicle
Anterior thorax	Rotates shoulder anteriorly (throwing motion); assists with inhalation	Scapula; ribs	Scapula: depresses; ribs: elevates	Pectoralis minor	Anterior surfaces of certain ribs (2–4 or 3–5)	Coracoid process of scapula
Anterior thorax	Moves arm from side of body to front of body; assists with inhalation	Scapula; ribs	Scapula: protracts; ribs: elevates	Serratus anterior	Muscle slips from certain ribs (1–8 or 1–9)	Anterior surface of vertebral border of scapula
Posterior thorax	Elevates shoulders (shrugging); pulls shoulder blades together; tilts head backwards	Scapula; cervical spine	Scapula: rotests inferiorly, retracts, elevates, and depresses; spine: extends	Trapezius	Skull; vertebral column	Acromion and spine of scapula; clavicle
Posterior thorax	Stabilizes scapula during pectoral girdle movement	Scapula	Retracts; rotates inferiorly	Rhomboid major	Thoracic vertebrae (T2–T5)	Medial border of scapula
Posterior thorax	Stabilizes scapula during pectoral girdle movement	Scapula	Retracts; rotates inferiorly	Rhomboid minor	Cervical and thoracic vertebrae (C7 and T1)	Medial border of scapula

Muscles That Move the Humerus

Similar to the muscles that position the pectoral girdle, muscles that cross the shoulder joint and move the humerus bone of the arm include both axial and scapular muscles (Figure 2 and Figure 3). The two axial muscles are the pectoralis major and the latissimus dorsi. The pectoralis major is thick and fan-shaped, covering much of the superior portion of the anterior thorax. The broad, triangular latissimus dorsi is located on the inferior part of the back, where it inserts into a thick connective tissue shealth called an aponeurosis.

The top left panel shows the lateral view of the pectoral and back muscles. The top right panel shows the posterior view of the right deltoid and the left back muscle. The bottom left panel shows the anterior view of the deep muscles of the left shoulder, and the bottom right panel shows the deep muscles of the left shoulder.

This table describes the muscles that move the humerus. The pectoralis major is an axial muscle that brings the elbows together and moves the elbows up (as during an uppercut punch). It originates in the clavicle, sternum, cartilage of ribs 1 through 6 or 1 through 7, and the aponeurosis of the external oblique muscle. The latissimus dorsi is an axial muscle that moves the elbow back (as in elbowing someone standing behind you) or spreads the elbows apart. It originates in the thoracic vertebrae (T7 through T12), the lower vertebrae, ribs 9 through 12, and the iliac crest. The deltoid is a scapular muscle that lifts arms at the shoulder. It originates in the trapezius, clavicle, acromion, and spine of scapula. The subscapularis is a scapular muscle that assists the pectoralis major in bringing the elbows together and stabilizes the shoulder joint during movement of the pectoral girdle. It originates in the subscapular fossa of the scapula. The supraspinatus is a scapular muscle that rotates the elbow outwards, as during a tennis swing. It originates in the supraspinous fossa of the scapula. The infraspinatus is a scapular muscle that rotates the elbow outwards, as during a tennis swing. It originates in the infraspinous fossa of the scapula. The teres major is a scapular muscle that assists the infraspinatus in rotating the elbow outwards. It originates in the posterior surface of the scapula. The teres minor is a scapular muscle that assists the infraspinatus in rotating the elbow outwards. It originates in the lateral border of the dorsal scapular surface. The coracobra chialis is a scapular muscle that moves the elbow up and across the body, as when putting a hand on the chest. It originates in the coracoid process of the scapula. — Figure 3. Muscles That Move the Humerus

The rest of the shoulder muscles originate on the scapula. The anatomical and ligamental structure of the shoulder joint and the arrangements of the muscles covering it, allows the arm to carry out different types of movements. The deltoid, the thick muscle that creates the rounded lines of the shoulder is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation. The subscapularis originates on the anterior scapula and medially rotates the arm. Named for their locations, the supraspinatus (superior to the spine of the scapula) and the infraspinatus (inferior to the spine of the scapula) abduct the arm, and laterally rotate the arm, respectively. The thick and flat teres major is inferior to the teres minor and extends the arm, and assists in adduction and medial rotation of it. The long teres minor laterally rotates and extends the arm. Finally, the coracobrachialis flexes and adducts the arm.

The tendons of the deep subscapularis, supraspinatus, infraspinatus, and teres minor connect the scapula to the humerus, forming the rotator cuff (musculotendinous cuff), the circle of tendons around the shoulder joint. When baseball pitchers undergo shoulder surgery it is usually on the rotator cuff, which becomes pinched and inflamed, and may tear away from the bone due to the repetitive motion of bring the arm overhead to throw a fast pitch.

Muscles That Move the Forearm

The forearm, made of the radius and ulna bones, has four main types of action at the hinge of the elbow joint: flexion, extension, pronation, and supination. The forearm flexors include the biceps brachii, brachialis, and brachioradialis. The extensors are the triceps brachii and anconeus. The pronators are the pronator teres and the pronator quadratus, and the supinator is the only one that turns the forearm anteriorly. When the forearm faces anteriorly, it is supinated. When the forearm faces posteriorly, it is pronated.

The biceps brachii, brachialis, and brachioradialis flex the forearm. The two-headed biceps brachii crosses the shoulder and elbow joints to flex the forearm, also taking part in supinating the forearm at the radioulnar joints and flexing the arm at the shoulder joint. Deep to the biceps brachii, the brachialis provides additional power in flexing the forearm. Finally, the brachioradialis can flex the forearm quickly or help lift a load slowly. These muscles and their associated blood vessels and nerves form the anterior compartment of the arm (anterior flexor compartment of the arm) (Figure 4 and Figure 5).

This multipart figure shows the different muscles that move the forearm. The major muscle groups are labeled.

This table describes the muscles that move the forearm. The biceps brachii are anterior muscles that perform a bicep curl; they also allow the palm of the hand to point toward the body while flexing. They originate in the coracoid process and the tubercle above the glenoid cavity. The brachialis originates in the front of the distal humerus. The brachioradialis is an anterior muscle that assists and stablizes the elbow during bicep-curl motion. It originates in the lateral supracondylar ridge at the distal end of the humerus. The triceps brachii are posterior muscles that extend the forearm, as during a punch. They originate in the infraglenoid tubercle of the scapula, the posterior shaft of the humerus, and the posterior humeral shaft distal to the radial groove. The aconeus is a posterior muscle that assists in extending the forearm; it also allows the forearm to extend away from the body. It originates in the lateral epicondyle of the humerus. The pronator teres is an anterior muscle that turns the hand palm-down. It originates in the medial epicondyle of the humerus and the coronoid process of the ulna. The pronator quadratus is an anterior muscle that assists in turning the hand palm-down. It originates in the distal portion of the anterior ulnar shaft. The supinator is a posterior muscle that turns the hand palm-down. It originates in the lateral epicondyle of the humerus and the proximal ulna. — Figure 5. Muscles That Move the Forearm

Muscles That Move the Wrist, Hand, and Fingers

Wrist, hand, and finger movements are facilitated by two groups of muscles. The forearm is the origin of the extrinsic muscles of the hand. The palm is the origin of the intrinsic muscles of the hand.

Muscles of the Arm That Move the Wrists, Hands, and Fingers

The muscles in the anterior compartment of the forearm (anterior flexor compartment of the forearm) originate on the humerus and insert onto different parts of the hand. These make up the bulk of the forearm. From lateral to medial, the superficial anterior compartment of the forearm includes the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis. The flexor digitorum superficialis flexes the hand as well as the digits at the knuckles, which allows for rapid finger movements, as in typing or playing a musical instrument (see Figure 6 and Table 9). However, poor ergonomics can irritate the tendons of these muscles as they slide back and forth with the carpal tunnel of the anterior wrist and pinch the median nerve, which also travels through the tunnel, causing Carpal Tunnel Syndrome. The deep anterior compartment produces flexion and bends fingers to make a fist. These are the flexor pollicis longus and the flexor digitorum profundus.

The muscles in the superficial posterior compartment of the forearm (superficial posterior extensor compartment of the forearm) originate on the humerus. These are the extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and the extensor carpi ulnaris.

The muscles of the deep posterior compartment of the forearm (deep posterior extensor compartment of the forearm) originate on the radius and ulna. These include the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis (see Figure 6).

This table describes the muscles that move the wrist, hands, and forearm. These muscles make up the superficial anterior compartment of the forearm. The flexor carpi radialis bends the wrist toward the body; it also tilts the hand to the side away from the body. It originates in the medial epicondyle of the humerus. The palmaris longus assists in bending the hand up toward the shoulder. It originates in the medial epicondyle of the humerus. The flexor carpi ulnaris assists in bending the hand up toward the shoulder; it also tilts the hand to the side away from the body and stabilizes the wrist. It originates in the medial epicondyle of the humerus, the olecranon process, and the posterior surface of the ulna. The flexor digitorum superficialis bends the fingers to make a fist. It originates in the medial epicondyle of the humerus, the coronoid process of the ulna, and the shaft of the radius. These muscles make up the deep anterior compartment of the forearm. The flexor pollicis longus bends the tip of the thumb. It originates in the anterior surface of the radius and the interosseous membrane. The flexor digitorum profundus bends the fingers to make a fist; it also bends the wrist toward the body. It originates in the coronoid process, the anteromedial surface of the ulna, and the interosseous membrane. These muscles make up the superficial posterior compartment of the forearm. The extensor radialis longus straightens the wrist away from the body; it also tilts the hand to the side away from the body. It originates in the lateral supracondylar ridge of the humerus. The extensor carpi radialis brevis assists the extensor radialis longus in extending and abducting the wrist; it also stabilizes the hand during finger flexion. It originates in the lateral epicondyle of the humerus. The extensor digitorum opens the fingers and moves them sideways away from the body. It originates in the lateral epicondyle of the humerus. The extensor digiti minimi extends the little finger. It originates in the lateral epicondyle of the humerus. The extensor carpi ulnaris straightens the wrist away from the body; it also tilts the hand to the side toward the body. It originates in the lateral epicondyle of the humerus and the posterior of the ulna. These muscles make up the deep posterior compartment of the forearm. The abductor pollicis longus moves the thumb sideways toward the body; it also extends the thumb and moves the hand sideways toward the body. It originates in the posterior surface of the radius and ulna and in the interosseous membrane. The extensor pollicis brevis extends the thumb. It originates in the dorsal shaft of the radius and ulna and in the interosseous membrane. The extensor pollicis longus extends the thumb. It originates in the dorsal shaft of the radius and ulna and in the interosseous membrane. The extensor indicis extends the index finger; it also straightens the wrist away from the body. It originates in the posterior surface of the distal ulna and in the interosseous membrane. — Figure 6. Muscles That Move the Wrist, Hands, and Forearm

The tendons of the forearm muscles attach to the wrist and extend into the hand. Fibrous bands called retinacula sheath the tendons at the wrist. The flexor retinaculum extends over the palmar surface of the hand while the extensor retinaculum extends over the dorsal surface of the hand.

Intrinsic Muscles of the Hand

The intrinsic muscles of the hand both originate and insert within it (Figure 7). These muscles allow your fingers to also make precise movements for actions, such as typing or writing. These muscles are divided into three groups. The thenar muscles are on the radial aspect of the palm. The hypothenar muscles are on the medial aspect of the palm, and the intermediate muscles are midpalmar.

The thenar muscles include the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, and the adductor pollicis. These muscles form the thenar eminence, the rounded contour of the base of the thumb, and all act on the thumb. The movements of the thumb play an integral role in most precise movements of the hand.

The hypothenar muscles include the abductor digiti minimi, flexor digiti minimi brevis, and the opponens digiti minimi. These muscles form the hypothenar eminence, the rounded contour of the little finger, and as such, they all act on the little finger. Finally, the intermediate muscles act on all the fingers and include the lumbrical, the palmar interossei, and the dorsal interossei.

This multipart figure shows the intrinsic muscles of the hand with the major muscle groups labeled.

Intrinsic Muscles of the Hand (Table 9)
Muscle	Movement	Target	Target motion direction	Prime mover	Origin	Insertion
Thenar muscles	Moves thumb toward body	Thumb	Abduction	Abductor pollicis brevis	Flexor retinaculum; and nearby carpals	Lateral base of proximal phalanx of thumb
Thenar muscles	Moves thumb across palm to touch other fingers	Thumb	Opposition	Opponens pollicis	Flexor retinaculum; trapezium	Anterior of first metacarpal
Thenar muscles	Flexes thumb	Thumb	Flexion	Flexor pollicis brevis	Flexor retinaculum; trapezium	Lateral base of proximal phalanx of thumb
Thenar muscles	Moves thumb away from body	Thumb	Adduction	Adductor pollicis	Capitate bone; bases of metacarpals 2–4; front of metacarpal 3	Medial base of proximal phalanx of thumb
Hypothenar muscles	Moves little finger toward body	Little finger	Abduction	Abductor digiti minimi	Pisiform bone	Medial side of proximal phalanx of little finger
Hypothenar muscles	Flexes little finger	Little finger	Flexion	Flexor digiti minimi brevis	Hamate bone; flexor retinaculum	Medial side of proximal phalanx of little finger
Hypothenar muscles	Moves little finger across palm to touch thumb	Little finger	Opposition	Opponens digiti minimi	Hamate bone; flexor retinaculum	Medial side of fifth metacarpal
Intermediate muscles	Flexes each finger at metacarpo-phalangeal joints; extends each finger at interphalangeal joints	Fingers	Flexion	Lumbricals	Palm (lateral sides of tendons in flexor digitorum profundus)	Fingers 2–5 (lateral edges of extensional expansions on first phalanges)
Intermediate muscles	Adducts and flexes each finger at metacarpo-phalangeal joints; extends each finger at interphalangeal joints	Fingers	Adduction; flexion; extension	Palmar interossei	Side of each metacarpal that faces metacarpal 3 (absent from metacarpal 3)	Extensor expansion on first phalanx of each finger (except finger 3) on side facing finger 3
Intermediate muscles	Abducts and flexes the three middle fingers at metacarpo-phalangeal joints; extends the three middle fingers at interphalangeal joints	Fingers	Abduction; flexion; extension	Dorsal interossei	Sides of metacarpals	Both sides of finger 3; for each other finger, extensor expansion over first phalanx on side opposite finger 3

Chapter Review

The clavicle and scapula make up the pectoral girdle, which provides a stable origin for the muscles that move the humerus. The muscles that position and stabilize the pectoral girdle are located on the thorax. The anterior thoracic muscles are the subclavius, pectoralis minor, and the serratus anterior. The posterior thoracic muscles are the trapezius, levator scapulae, rhomboid major, and rhomboid minor. Nine muscles cross the shoulder joint to move the humerus. The ones that originate on the axial skeleton are the pectoralis major and the latissimus dorsi. The deltoid, subscapularis, supraspinatus, infraspinatus, teres major, teres minor, and coracobrachialis originate on the scapula.

The forearm flexors include the biceps brachii, brachialis, and brachioradialis. The extensors are the triceps brachii and anconeus. The pronators are the pronator teres and the pronator quadratus. The supinator is the only one that turns the forearm anteriorly.

The extrinsic muscles of the hands originate along the forearm and insert into the hand in order to facilitate crude movements of the wrists, hands, and fingers. The superficial anterior compartment of the forearm produces flexion. These muscles are the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexor digitorum superficialis. The deep anterior compartment produces flexion as well. These are the flexor pollicis longus and the flexor digitorum profundus. The rest of the compartments produce extension. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris are the muscles found in the superficial posterior compartment. The deep posterior compartment includes the abductor longus, extensor pollicis brevis, extensor pollicis longus, and the extensor indicis.

Finally, the intrinsic muscles of the hands allow our fingers to make precise movements, such as typing and writing. They both originate and insert within the hand. The thenar muscles, which are located on the lateral part of the palm, are the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, and adductor pollicis. The hypothenar muscles, which are located on the medial part of the palm, are the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi. The intermediate muscles, located in the middle of the palm, are the lumbricals, palmar interossei, and dorsal interossei.

Review Questions

1. The rhomboid major and minor muscles are deep to the ________.

rectus abdominis
scalene muscles
trapezius
ligamentum nuchae

2. Which muscle extends the forearm?

biceps brachii
triceps brachii
brachialis
deltoid

3. What is the origin of the wrist flexors?

the lateral epicondyle of the humerus
the medial epicondyle of the humerus
the carpal bones of the wrist
the deltoid tuberosity of the humerus

4. Which muscles stabilize the pectoral girdle?

axial and scapular
axial
appendicular
axial and appendicular

Critical Thinking Questions

1. The tendons of which muscles form the rotator cuff? Why is the rotator cuff important?

2. List the general muscle groups of the shoulders and upper limbs as well as their subgroups.

Glossary

abductor digiti minimi: muscle that abducts the little finger

adductor pollicis: muscle that adducts the thumb

abductor pollicis brevis: muscle that abducts the thumb

abductor pollicis longus: muscle that inserts into the first metacarpal

anconeus: small muscle on the lateral posterior elbow that extends the forearm

anterior compartment of the arm: (anterior flexor compartment of the arm) the biceps brachii, brachialis, brachioradialis, and their associated blood vessels and nerves

anterior compartment of the forearm: (anterior flexor compartment of the forearm) deep and superficial muscles that originate on the humerus and insert into the hand

biceps brachii: two-headed muscle that crosses the shoulder and elbow joints to flex the forearm while assisting in supinating it and flexing the arm at the shoulder

brachialis: muscle deep to the biceps brachii that provides power in flexing the forearm.

brachioradialis: muscle that can flex the forearm quickly or help lift a load slowly

coracobrachialis: muscle that flexes and adducts the arm

deep anterior compartment: flexor pollicis longus, flexor digitorum profundus, and their associated blood vessels and nerves

deep posterior compartment of the forearm: (deep posterior extensor compartment of the forearm) the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis, and their associated blood vessels and nerves

deltoid: shoulder muscle that abducts the arm as well as flexes and medially rotates it, and extends and laterally rotates it

dorsal interossei: muscles that abduct and flex the three middle fingers at the metacarpophalangeal joints and extend them at the interphalangeal joints

extensor carpi radialis brevis: muscle that extends and abducts the hand at the wrist

extensor carpi ulnaris: muscle that extends and adducts the hand

extensor digiti minimi: muscle that extends the little finger

extensor digitorum: muscle that extends the hand at the wrist and the phalanges

extensor indicis: muscle that inserts onto the tendon of the extensor digitorum of the index finger

extensor pollicis brevis: muscle that inserts onto the base of the proximal phalanx of the thumb

extensor pollicis longus: muscle that inserts onto the base of the distal phalanx of the thumb

extensor radialis longus: muscle that extends and abducts the hand at the wrist

extensor retinaculum: band of connective tissue that extends over the dorsal surface of the hand

extrinsic muscles of the hand: muscles that move the wrists, hands, and fingers and originate on the arm

flexor carpi radialis: muscle that flexes and abducts the hand at the wrist

flexor carpi ulnaris: muscle that flexes and adducts the hand at the wrist

flexor digiti minimi brevis: muscle that flexes the little finger

flexor digitorum profundus: muscle that flexes the phalanges of the fingers and the hand at the wrist

flexor digitorum superficialis: muscle that flexes the hand and the digits

flexor pollicis brevis: muscle that flexes the thumb

flexor pollicis longus: muscle that flexes the distal phalanx of the thumb

flexor retinaculum: band of connective tissue that extends over the palmar surface of the hand

hypothenar: group of muscles on the medial aspect of the palm

hypothenar eminence: rounded contour of muscle at the base of the little finger

infraspinatus: muscle that laterally rotates the arm

intermediate: group of midpalmar muscles

intrinsic muscles of the hand: muscles that move the wrists, hands, and fingers and originate in the palm

latissimus dorsi: broad, triangular axial muscle located on the inferior part of the back

lumbrical: muscle that flexes each finger at the metacarpophalangeal joints and extend each finger at the interphalangeal joints

opponens digiti minimi: muscle that brings the little finger across the palm to meet the thumb

opponens pollicis: muscle that moves the thumb across the palm to meet another finger

palmar interossei: muscles that abduct and flex each finger at the metacarpophalangeal joints and extend each finger at the interphalangeal joints

palmaris longus: muscle that provides weak flexion of the hand at the wrist

pectoral girdle: shoulder girdle, made up of the clavicle and scapula

pectoralis major: thick, fan-shaped axial muscle that covers much of the superior thorax

pectoralis minor: muscle that moves the scapula and assists in inhalation

pronator quadratus: pronator that originates on the ulna and inserts on the radius

pronator teres: pronator that originates on the humerus and inserts on the radius

retinacula: fibrous bands that sheath the tendons at the wrist

rhomboid major: muscle that attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae

rhomboid minor: muscle that attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae

rotator cuff: (also, musculotendinous cuff) the circle of tendons around the shoulder joint

serratus anterior: large and flat muscle that originates on the ribs and inserts onto the scapula

subclavius: muscle that stabilizes the clavicle during movement

subscapularis: muscle that originates on the anterior scapula and medially rotates the arm

superficial anterior compartment of the forearm: flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, and their associated blood vessels and nerves

superficial posterior compartment of the forearm: extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and their associated blood vessels and nerves

supinator: muscle that moves the palm and forearm anteriorly

supraspinatus: muscle that abducts the arm

teres major: muscle that extends the arm and assists in adduction and medial rotation of it

teres minor: muscle that laterally rotates and extends the arm

thenar: group of muscles on the lateral aspect of the palm

thenar eminence: rounded contour of muscle at the base of the thumb

trapezius: muscle that stabilizes the upper part of the back

triceps brachii: three-headed muscle that extends the forearm

Solutions

Answers for Review Questions

C
B
B
A

Answers for Critical Thinking Questions

Tendons of the infraspinatus, supraspinatus, teres minor, and the subscapularis form the rotator cuff, which forms a foundation on which the arms and shoulders can be stabilized and move.
The muscles that make up the shoulders and upper limbs include the muscles that position the pelvic girdle, the muscles that move the humerus, the muscles that move the forearm, and the muscles that move the wrists, hands, and fingers.

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