Muscles Of The Forearm

Front 1

Bony Landmarks - distal forearm

Radius

Back 1

1) lateral side of forearm
a) distal end of radius: styloid process, ulnar notch, dorsal tubercle
1) styloid process of radius extends 1 cm more distally than ulnar styloid process - limits abduction of hand at wrist
2) ulnar notch of radius articulates with distal end of ulna - provides for pronation-supination motions
3) distal radius articulates with proximal carpal bones at radiocarpal joint (wrist)

Front 2

Bony Landmarks - distal forearm

Ulna

Back 2

1) medial side of forearm
a) distal end of ulna: styloid process
b) note: ulna does not articulate with carpal bones of wrist
2) shaft of radius and ulna joined together by interosseous membrane - dense fascia layer that also serves as area of origin for deep muscles of anterior & posterior forearm

Front 3

Bones of the wrist & hand

Wrist

Back 3

a) 8 carpal bones, in two rows of 4 bones ("Tiny toads can hop, so let them play")
1) distal row - (lateral to medial) - trapezium, trapezoid, capitate, hamate
2) proximal row - scaphoid, lunate, triquetral (triquetrum), pisiform
b) scaphoid & lunate carpal bones articulate with distal radius at radiocarpal joint
c) motions of wrist: flexion-extension, abduction-adduction, circumduction

Front 4

Bones of the wrist & hand

Hand

Back 4

a) metacarpal bones
1) first metacarpal (thumb) - free to move independent of other metacarpal bones
2) metacarpals 2-5 joined together by fascia, tendons, & muscles - form single unit
a) 2nd & 3rd metacarpals almost immobile
b) 4th metacarpal has limited anterior - posterior movement
c) 5th metacarpal has greatest degree of anterior - posterior movement
b) phalanges (phalanx bone) - 2 in thumb, 3 each in other digits (proximal, middle, distal phalanx bones)

Front 5

Forearm

Back 5

- divided into anterior (flexor) & posterior (extensor) compartments
1) covered by antebrachial fascia - 2 specializations distally:
a) extensor retinaculum - on dorsal side; restrains & compartmentalizes tendons of extensor muscles
b) flexor retinaculum - on ventral side; over tendons of flexor muscles
1) attached to styloid processes of distal radius and ulna
2) more distally, spans across carpal bones - forms carpal tunnel
3) continuation into palm as palmar aponeurosis (deep fascia of palmar hand)
2) movements:
a) contraction of lateral & medial muscles of flexor compartment - flexion of wrist
b) contraction of lateral & medial muscles of extensor compartment - extension of wrist
c) contraction of medial flexor & extensor muscles - adduction of wrist
d) contraction of lateral flexor & extensor muscles - abduction of wrist
e) contraction of central flexor muscles - flexion of digits
f) contraction of central extensor muscle - extension of digits

Front 6

Flexor Forearm Muscles

Back 6

1) flexor muscles used for grasping - more powerful than extensor muscles
2) originate from medial epicondyle of humerus (common flexor tendon) and anterior surfaces of radius, ulna & interosseous membrane
3) muscles of flexor (anterior) compartment found in 2 layers:
a) superficial - 5 muscles
b) deep - 3 muscles

Front 7

Superficial Muscles of Flexor Forearm:
x 5
1) Pronator Teres Muscle

Back 7

Origin - medial epicondyle of humerus (common flexor tendon)
Insert - lateral side of middle radius
Innerv - Median nerve
Action - assists pronator quadratus in pronation of forearm

Front 8

Superficial Muscles of Flexor Forearm:
x 5
2) Flexor Carpi Radialis muscle

Back 8

Origin - medial epicondyle of humerus (common flexor tendon)
Insert - metacarpal bone of lateral hand (radial side of hand)
Innerv - median nerve
Action - flexion, abduction of hand at wrist

Front 9

Superficial Muscles of Flexor Forearm:
x 5
3) Palmaris Longus Muscle

Back 9

- small muscle absent in 15% of population
Origin - medial epicondyle of humerus (common flexor tendon)
Insert - palmar aponeurosis
Innerv - median nerve
Action - flexion of hand at wrist

Front 10

Superficial Muscles of Flexor Forearm:
x 5
4) Flexor Digitorum Superficialis Muscle

Back 10

Origin - Medial epicondyle of humerus (common flexor tendon), proximal ends of anterior ulna & radius
Insert - via 4 tendons to middle phalynx bones of digits 2-5; tendons bifurcate just prior to insertion for passage of underlying flexor digitorum profundus tendons
Innerv - Median nerve
Action - flexion of digits 2-5

Front 11

Superficial Muscles of Flexor Forearm:
x 5
5) Flexor Carpi Ulnaris Muscle

Back 11

Origin - medial epicondyle of humerus (common flexor tendon) and proximal ulna
Insert - metacarpal bone of medial hand (ulnar side of hand)
- pisiform bone of wrist is sesamoid bone with tendon of flexor carpi ulnaris muscle
Innerv - Ulnar nerve
Action - flexion, adduction of hand at wrist

Front 12

Deep Muscles of Flexor Forearm:
x 3
1) Pronator Quatratus Muscle

Back 12

Origin - anterior side of distal ulna
Insert - anterior side of distal radius
Innerv - median Nerve
Action - primary (strongest) pronator of forearm (assisted by Pronator teres)

Front 13

Deep Muscles of Flexor Forearm:
x 3
2) Flexor Digitorum Profundus Muscle

Back 13

Origin - anterior ulna & interosseous membrane
Insert - via 4 tendons to distal phalynx bones, digits 2-5
- tendons pass through split in tendons of Flexor Digitorum Superficialis
Innerv - a) median nerve - to lateral 1/2 of muscle (for digits 2 & 3)
b) ulnar nerve - to medial 1/2 of muscle (for digits 4 & 5)
Action - flexion of digits 2-5

Front 14

Deep Muscles of Flexor Forearm:
x 3
3) Flexor Pollicis Longus Muscle

Back 14

Origin - anterior radius & interosseous membrane
Insert - distal phalynx bone & thumb
Innerv - Median Nerve
Action - flexion of thumb

Front 15

Golfer's Elbow

Back 15

1) from repetitive use f flexor muscles of forearm
2) pain felt in medial elbow - inflammation (tendonitis) of common flexor tendon

Front 16

Extensor Forearm & Dorsum of Hand

Back 16

1) 4 general types of extensor (posterior) compartment muscles (11 muscles total):
a) 3 muscles that extend teh wrist
b) 3 muscles that extend digits 2-5
c) 3 muscles that abduct or extend thumb (digit 1)
d) 2 muscles that do not act on wrist or digits (Brachioradialis & Supinator)
2) most extensor compartment muscles arise via common extensor tendon from lateral epicondyle of humerus, or from posterior interosseous membrane
3) extensor compartment muscles divided into:
a) superficial muscles - six
b) deep muscles - five

Front 17

Superficial Muscles of Extensor Compartment:
x 6
1) Extensor Carpi Radialis Longus Muscle

Back 17

Origin - lateral epicondyle of humerus (common extensor tendon)
Insert - metacarpal bone of lateral hand (radial side of hand)
Innerv - Radial nerve
Action - extend, abduct hand at wrist

Front 18

Superficial Muscles of Extensor Compartment:
x 6
2) Extensor Carpi Radialis Brevis Muscle

Back 18

Origin - lateral epicondyle of humerus (common extensor tendon)
Insert - metacarpal bone of central hand
Innerv - radial nerve
Action - extend hand at wrist

Front 19

Superficial Muscles of Extensor Compartment:
x 6
3) Extensor Digitorum Muscle

Back 19

Origin - lateral epicondyle of humerus (common extensor tendon)
Insert - via 4 tendons to phalynx bones of digits 2-5; forms Extensor Expansion
Innerv - Radial Nerve
Action - extension of digits 2-5
- tendons interconnected on dorsum of hand by tendinous bands - prevent completely independent extension of digits
- Extensor Expansion - dense connective tissue sheath that covers dorsum of digits 2-5
- receives tendons of: extensor digitorum, extensor indicis, extensor digiti minimi, & lumbrical muscles (from central palm of hand)

Front 20

Superficial Muscles of Extensor Compartment:
x 6
4) Extensor Digiti Minimi Muscle

Back 20

Origin - lateral epicondyle of humerus (common extensor tendon)
Insert - extensor expansion of digit 5
Innerv - Radial Nerve
Action - extends 5th digit

Front 21

Superficial Muscles of Extensor Compartment:
x 6
5) Extensor Carpi Ulnaris Muscle

Back 21

origin - lateral epicondyle of humerus (common extensor tendon) and posterior ulna
Insert - metacarpal bone of medial hand (ulonar side of hand)
innerv - radial nerve
Action 0 extend, adduct hand at wrist

Front 22

Superficial Muscles of Extensor Compartment:
x 6
6) Brachioradialis Muscle

Back 22

Origin - lateral epicondyle of humerus (common extensor tendon)
Insert - lateral side, distal radius
- passes anterior to elbow joint
Innerv - Radial nerve
Action - flexes forearm at elbow
- despit it's action, brachioradialis is included witht eh extensor muscles because it arises from teh common extensor tendon & is innervated by the radial nerve

Front 23

Deep Muscles of Extensor Forearm Compartment
x 5
1) Supinator Muscle

Back 23

Origin - lateral epicondyle (common extensor tendon) and posterior ulna
Insert - proximal 1/3 of radius
Innerv - radial nerve
Action - supinates forearm
- primary supinator of forearm, but is weak muscle; biceps brachii muscle recruited when greater force is required

Front 24

Deep Muscles of Extensor Forearm Compartment
x 5
2) Extensor Indicis Muscle

Back 24

origin - posterior ulna & interosseous membrane
Insert - extensor expansion of digit 2 (index finger)
Innerv - radial nerve
Action - independent extension of digit 2

Front 25

Deep Muscles of Extensor Forearm Compartment
x 5
3) Abductor Pollicis Longus Muscle

Back 25

Origin - posterior radius, ulna & interosseous membrane
Insert - 1st (thumb) metacarpal bone (lateral side)
Innerv - Radial nerve
Action - abducts thumb

Front 26

Deep Muscles of Extensor Forearm Compartment
x 5
4) Extensor Pollicic Longus Muscle

Back 26

Origin - posterior ulna & interosseous membrane
Insert - distal phalynx of thumb
Innerv - radial nerve
Action - extension of thumb

Front 27

Deep Muscles of Extensor Forearm Compartment
x 5
5) Extensor Pollicis Brevis Muscle

Back 27

Origin - posterior radius & interosseous membrane
Insert - proximal phalynx of thumb
Innerv - radial nerve
Action - extension of the thumb - extrinsic thumbs muscle (abductor pollicis longus, extensor pollicis longus & brevis) emerge from deep forearm along lateral side of extensor digitorum muscle

Front 28

Anatomical Snuff Box

Back 28

- tendons of extrinsic thumb muscles form Anatomical Snuff Box at lateral wrist - tendons of abductor pollicis longus & extensor pollicis brevis run together along lateral side of wrist; tendon of extensor pollicis longus crosses posterior side of wrist in groove medial to dorsal radial tubercle of radius, then bends sharply to run down posterior thumb

Front 29

Arrangement of extensor (posterior) forearm muscles

Back 29

3 - muscles act on wrist
3 - muscles act on fingers 2-5
3 - muscles oct on thumb
2 - do not act on hand/wrist (pronator/supinator)

Front 30

Tennis Elbow

Back 30

1) from repettive forceful supination & extension of forearm & hand (backhand tennis stroke)
2) pain felt in lateral elbow - inflammation (tendonitis) of common extensor tendon

Front 31

Cubital Fossa

Back 31

- on anterior side of elbow joint; boundaries:
a) lateral - brachioradialis muscle (origin = lateral epicondyle of humerus)
b) medial - pronator teres muscle (origin = medial epicondyle of humerus)
c) roof - bicipital aponeurosis of biceps brachii muscle (to medial antebrachial fascia)

Front 32

Wrist

Back 32

1) formed by carpal bones articulations with distal radius (radiocarpal joint)
2) 15 forearm muscles (9 extensors, 6 flexors) send a total of 24 tendons across the wrist
a) tendons are held within compartments formed by the Extensor & Flexor Retinacula
b) these maintain tendons in precise relationship to each other & prevent "bowstringing"
c) the posterior surfaces of distal radius & ulna are grooved for passage of the extensor tendons

Front 33

Flexor Retinaculum

Back 33

a) continues distally to span medial-lateral across the carpal bones - forms Carpal Tunnel
1) 9 tendons and one major nerve pass through carpal tunnel to enter palm of hand:
- tendons of Flexor Digitorum Superficialis muscle (4), Flexor Digitorum Profundus muscle (4), & Flexor Pollicis Longus Muscle (1), plus the median nerve