SECTION 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.

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

REVIEW QUESTIONS

CRITICAL THINKING QUESTIONS