ANATCELL: Muscles of Forearm & Hand

Muscles of Forearm: Extensors

Superficial

• Anconeus

• Extensor carpi ulnaris

• Extensor carpi radialis brevis & longus

• Extensor digitorum

• Extensor digit minimi

Deep

• Supinator

• Extensor Indicis

• Extensor pollicis brevis & longus

• Abductor pollicis longus

Flexors

Superficial

• Pronator teres

• Flexor carpi radialis

• Flexor Carpi ulnaris

• Palmaris longus

• brachioradialis (posterior compartment)

Middle

• flexer digitorum superficialis

Deep

• Pronator quadratus

• Flexor digitorum profundus

• Flexor pollicis longus

Supinator

small triangular muscle → deep across back of elbow

• Origin: humerus (lateral epicondyle); proximal ulna

• Insertion: radius

• Action: assists triceps brachii in forcible supination of forearm

• Innervation: radial nerve (posteror interosseus nerve, C6 & C7)

Extensor Indicis

thin muscle deep in the posterior forearm

• Origin: Ulna (posterior surface of distal end)

• Insertion: head of 2nd metacarpal (index finger)

• Action: extends index finger & assist in hand extension

• Innervation: radial nerve (posteror interosseus nerve, C6 & C7)

Extensor pollicis longus

thin muscle of posterior forearm & thumb

• Origin: ulna

• Insertion: 1st distal phalanx

• Action: abducts & extends the thumb

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Extensor pollicis brevis

thin muscle of posterior forearm & thumb

• Origin: dorsal shaft of radius & ulna

• Insertion: base of proximal phalanx of thumb

• Action: extends the thumb

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Abductor pollicis longus

thin muscle of posterior forearm & thumb

• Origin: posterior surface of radius & ulna

• Insertion: base of 1st metacarpal & trapezium

• Action: abducts & extends the thumb

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Anconeus

small triangular muscle on lateral side of elbow

• Origin: humerus (lateral epicondyle)

• Insertion: olecranon on ulna

• Action: abducts ulna during forearm pronation; synergist of triceps brachii in elbow extension

• Innervation: radial nerve

Extensor carpi ulnaris

thin muscle that lies superficially in posterior forearm

• Origin: lateral epicondyle & posterior border of ulna

• Insertion: base of 5th metacarpal

• Action: extends & adducts wrists

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Extensor carpi radialis longus

parallels brachioradialis on lateral forearm

• Origin: lateral supracondylar ridge

• Insertion: base of 2nd metacarpal

• Action: extends & abducts hand w/ extensor/flexor carpi ulnaris

• Innervation: radial nerve (C5 & C6)

Extensor carpi radialis brevis

shorter than extensor carpi radialis longus & lies deep to it

• Origin: lateral epicondyle of humerus

• Insertion: base of 3rd metacarpal

• Action: extends & abducts hand; acts synergistically w/ extensor carpi radialis longus to steady wrist during finger flexion

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Extensor digitorum

thin muscle of the posterior forearm; divides into 4 tendons distally

• Origin: lateral epicondyle of humerus

• Insertion: by four tendons into extensor expansions & distal phalanges of (fingers 2-5)

• Action: prime mover of finger extension; can abduct/flare fingers 2-5

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Extensor digiti minimi

thin muscle of posterior forearm & little finger

• Origin: lateral epicondyle of humerus

• Insertion: little finger

• Action: extends little finger

• Innervation: radial nerve (posterior interosseus nerve, C7& C8 )

Brachioradialis

thin muscle on front of forearm

• Origin: proximal 23 lateral supracondylar ridge

• Insertion: radius (styloid process)

• Action: synergist in forearm flexion (at elbow)

• Innervation: radial nerve

Pronator quadratus

small square muscle that lies on anterior distal forearm

• Origin: distal portion of anterior ulna

• Insertion: distal surface of radius

• Action: prime mover of forearm pronation; acts w/ pronator teres, stabilizes distal ends of radius & ulna

• Innervation: medial nerve (C7& C8)

Flexor digitorum profundus

thin muscle of anterior forearm; divides into 4 thin tendons distally

• Origin: medial & anterior surface of ulna & interosseus membrane

• Insertion: bases of distal phalanges 2-5

• Action: flexes distal phalanxes (2-5), assists with flexion of hand

• Innervation:

  • medial part: ulnar nerve;

  • lateral part: median nerve (C7-C8)

Flexor pollicis longus

thin muscle of anterior forearm & thumb

• Origin: anterior surface of radius & interosseus membrane

• Insertion: base of 1st distal phalanx

• Action: flexes phalanges of digit 1 at interphalangeal

• Innervation: branch of median nerve (C7 & C8)

Pronator Teres

thin muscle that crosses front elbow

• Origin: medial epicondyle & coronoid process (ulna)

• Insertion: lateral end of radius

• Action: flexes elbow & pronates forearm

  • pronation occurs at radioulnar joint

• Innervation: median nerve (C6 & C7)

Flexor carpi radialis

thin muscle of anterior forearm

• Origin: medial epicondyle

• Insertion: base of 2nd metacarpal

• Action: powerful flexor of wrist/hand; abducts hand

• Innervation: median nerve (C7 & C8)

Flexor carpi ulnaris

thin muscle of anterior forearm & thumb

• Origin: medial epicondyle; olecranon & posterior border of ulna

• Insertion: 5th metacarpal, pisiform, hamate

• Action: flexes & adducts wrist

• Innervation: ulnar nerve (C8 & T1)

Flexor digitorum superficialis

thin muscle of the anterior forearm; divides into 4 tendons (middle layer)

• Origin: medial epicondyle; cornoid process;

  • radial head (superior ½ of anterior border of radius)

• Insertion: middle phalanges (2-5)

• Action: flexes hand & middle fingers 2-5

• Innervation: median nerve (C7, C8 & T1)

Palmaris longus

muscle of forearm

• Origin: medial epicondyle

• Insertion: palmar aponeurosis

• Action: weakly flexes wrist

• Innervation: ulnar nerve (C8 & T1)

Muscles of Hand: Thenar Group

controls movement of thumb in all directions (abduct, adduct, extend, flex & oppose)

• Adductor pollicis

• Abductor pollicis brevis

• Opponens pollicis

• Flexor pollicis brevis

Adductor pollicis

triangular muscle w/ 2 heads that lie in palm

• Origin: proximal phalanx & 3rd metacarpal

• Insertion: 1st proximal phalanx & 1st metacarpal

• Action: helps to adduct & oppose thumb

• Innervation: ulnar nerve (C8 & T1)

Abductor Pollicis Brevis (superficial)

short muscle on the superficial part of thenar eminence

• Origin: flexor retinaculum & nearby carpals (trapezium & scaphoid)

• Insertion: 1st proximal phalanx (base)

• Action: abducts the thumb

• Innervation: median nerve (C8 & T1)

Opponens Pollicis (deep)

short muscle that forms deep part of thenar eminence

• Origin: flexor retinaculum & nearby carpals (trapezium & scaphoid)

• Insertion: lateral side of 1st metacarpal

• Action: opposition: moves thumb to touch little finger

• Innervation: median nerve

Flexor Pollicis Brevis

thin muscle; forms part of the thenar eminence

• Origin: flexor retinaculum (trapezium, trapezoid, capitate)

• Insertion: proximal phalanx (lateral side of its base)

• Action: flexes thumb

• Innervation: median nerve (occassionaly ulnar nerve)

Hypothenar Group

• Flexi digiti minimi brevis

• Abductor digiti minimi

• Opponens digit minimi

Flexor Digiti Minimi Brevis (superficial)

thin muscle that forms superficial part of hypothenar eminene

• Origin: flexor retinaculum & hamate

• Insertion: 5th proximal phalanx (medial side)

• Action: flexes little finger

• Innervation: ulnar nerve

Abductor digiti minimi

thin muscle in superficial part of hypothenar eminence

• Origin: pisiform bone

• Insertion: 5th proximal phalanx (medial side of base)

• Action: abduct little finger

• Innervation: ulnar nerve (C8 & T1)

Opponens digit minimi (deep)

thin muscle that forms deep part of hypothenar eminence

• Origin: flexor retinaculum & hamate

• Insertion: 5th metacarpal

• Action: helps to oppose little finger to thumb

• Innervation: ulnar nerve (C8 & T1)

Mid Palmer Group

• Palmer Interossei

• Dorsal Interossei

• Lumbricals

Palmer Interossei

three muscles that lie between metacarpals in palm of hand (absent from middle finger)

• Origin: metacarpals 2-5

• Insertion: proximal phalanges 2-5 (medial aspect)

• Action: assists in adduction & flexion of metacarpophalangeal joints of fingers 2-5; extension at interphalangeal joints

• Innervation: ulnar nerve

Dorsal Interossei

four muscles that lie between metacarpals in dorsum of hand

• Origin: metacarpals 2-5

• Insertion: proximal phalanges 2-5

• Action: abduction & flexion at metacarpophalangeal joints; extension at interphalangeal joints

• Innervation: ulnar nerve

Lumbricals

four thin muscles that lie in palm of hand

• Origin: flexor digitorum profundus

• Insertion: proximal phalanges 2-5

• Action: flex metacarpohalangeal joints of digits 2-5 & extend at interphalangeal joints of fingers 2-5

• Innervation: median nerve (lateral 1& 2); ulnar nerve (medial 3& 4)