forarm muscles

1. Forearm muscles

2. Compartments
• Forearm is divided into
• Anterior and posterior compartments by
• Lateral intermuscular septum
• Aninterosseousmembrane
• Attachment of deepfasciaalongtheposterior border of the
ulna

3. Anterior (flexor) compartment of forearm
• Muscles are in threelayers
• Superficial
• Intermediate
• Deep
• Thesemusclesassociatedwith
• Movements of wristjoint
• Flexionof fingers
• Pronation
• All muscles in anterior compartment of
forearm
• Innervated by median nerve
• Except for Flexor carpi ulnaris muscle and
medial half of Flexor digitorum profundus
muscle
• Innervated byulnarnerve

4. Anterior compartment of forearm
• Superficial group
• Five muscles cross the elbow joint
• Three musclesdonot
• Flexor compartment is much more
bulky
• Than extensor compartment
• Necessary power of grip

5. Pronator Teres
• Origin
• Humeral head
• Medial epicondyle of humerus
• Ulnar head
• Medial border of coronoid process of ulna
• Action
• Lateral aspect of shaft of radius
• Nerve supply
• Median nerve
• Action
• Pronation and flexion of forearm

6. Flexor carpi radialis
• Origin
• Medial epicondyle of humerus
• Insertion
• Bases of second and third metacarpal bones
• Nerve supply
• Median nerve
• Action
• Flexes and abducts hand at wrist joint

7. Palmaris longus
• Origin
• Medial epicondyle of humerus
• Insertion
• Flexor retinaculum and palmar aponeurosis
• Nerve supply
• Median nerve
• Action
• Flexes hand

8. Flexor Carpi Ulnaris
• Origin
• Humeral head
• Medial epicondyle of humerus
• Ulnar head
• Medial aspect of olecranon process and posterior border of ulna
• Insertion
• Pisiform bone, hook of the hamate, base at fifth metacarpal
bone
• Nerve supply
• Ulnar nerve
• Action
• Flexes and adducts hand at wrist joint

9. Flexor Digitorum Superficialis
• Origin
• Humeroulnar head
• Medial epicondyle of humerus; medial border of coronoid process of
ulna
• Radial head
• Oblique line on anterior surface of shaft of radius
• Insertion
• Middle phalanx of medial four fingers
• Nerve supply
• Median nerve
• Action
• Flexes middle phalanx of fingers and assists in flexing proximal
phalanx and hand

10. Deep group
• 3 muscles
• Flexor digitorum profundus
• Flexor pollicis longus
• Pronator quadratus

11. Flexor digitorum profundus
• Origin
• Anteromedial surface of shaft of ulna
• Insertion
• Distal phalanges of medial four fingers
• Action
• Flexes distal phalanx of fingers; then assists in
flexion of middle and proximal phalanges and
wrist
• Nerve supply
• Ulnar (medial half) and median (lateral half)
nerves

12. Flexor pollicis longus
• Origin
• Anterior surface of shaft of radius
• Insertion
• Distal phalanx of thumb
• Action
• Flexes distal phalanx of thumb
• Nerve supply
• Anterior interosseous branch of median nerve

13. Pronator quadratus
• Origin
• Anterior surface of shaft of ulna
• Insertion
• Anterior surface of shaft of radius
• Action
• Pronates forearm
• Nerve Supply
• Anterior interosseous
• Branch of median nerve

14. Space of Parona
• Space in front of pronator quadratus
• Deep to long flexor tendons of fingers
and their synovial sheaths
• Limited proximally by
• Oblique origin of flexor digitorum
superficialis
• Space involved in proximal extensions
of synovial sheath infections
• Can be drained through radial and
ulnar incisions to the side of the flexor
tendons

15. Posterior compartment of forearm
• Muscles are arranged in 2 layers
• Superficial
• Deep
• Muscles are associated with
• Movement of the wristjoint
• Extension of the fingers and thumb
• Supination
• All the muscles of posterior compartment
are supplied by
• Radial nerve

16. Arrangement of posterior compartment muscles
• Upper part
• Anconeus (superficial)
• Supinator (deep)
• Lateral part of humerus
• Pass along the radial side
• Brachioradialis
• Extensors carpi radialis longus
• Extensors carpi radialis brevis
• Passing along posterior surface of the
forearm
• Extensor digitorum
• Extensor digiti minimi and
• Extensor carpi ulnaris
• At lower end of forearm
• These two groups are separated by
three muscles
• They emerge from deeply in between
them and go to the thumb
• Abductor pollicis longus
• Extensors pollicis longus and
• Extensors pollicis longus brevis
• One muscle for the forefinger runs
deeply to reach the back of the hand
• Extensor indicis

17. Superficial muscles of the back of forearm
• There are 7 muscles
• Common extensor origin
• Four of the superficialmuscles
• Arisefromthetipoflateralepicondyleof thehumerus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor digiti minimi, and
• Extensor carpi ulnaris
• All seven muscles cross elbow joint

18. Superficial muscles of back of forearm
• Categorized into two groups
• Lateral and posterior
• Each group consists of three muscles
• Lateral group
• Brachioradialis
• Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Posterior group
• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris
• In the upper end
• Anconeus

19. Brachioradialis
• Origin
• Upper 2/3rd of lateral supracondylar ridge of
humerus
• Insertion
• Into base of styloid process of radius
• Nerve Supply
• Radial nerve
• Action
• Flexion of the forearm (specially in midprone
position)

20. Extensor carpi radialis longus
• Origin
• From the lower 1/3rd of the lateral
supracondylar ridge of the humerus
• Insertion
• Into the posterior surface of the base of the
2nd metacarpal bone
• Nerve Supply
• Radial nerve
• Action
• Extension of the hand at wrist joint
Abduction of the hand at wrist joint

21. Extensor carpi radialis brevis
• Origin
• Lateral epicondyle of humerus (common extensor
origin)
• Insertion:
• Posterior surface of base of 3rd metacarpal bone
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension & abduction of the hand at wrist joint

22. Extensor digitorum
• Origin
• Lateral epicondyle of humerus (common extensor
origin)
• Insertion
• Extensor expansion of the medial 4 fingers
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension of metacarpophalangeal and
interphalangeal joints of the medial 4 fingers
• Extension of the hand at wrist joint

23. Extensor digiti minimi
• Origin
• Lateral epicondyle of the humerus (common
extensor origin)
• Insertion
• Extensor expansion of the little finger
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension of metacarpophalangeal and
interphalangeal joints of the little finger

24. Extensor carpi ulnaris
• Origin
• Lateral epicondyle of the humerus (common
extensor origin)
• Insertion
• Posterior surface of the base of the 5 th
metacarpal bone
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension & Adduction of the hand at
wrist joint

25. Anconeus
• Origin
• Posterior aspect of the lateral epicondyle of the
humerus
• Insertion
• Lateral surface of olecranon process of ulna
• Nerve Supply
• Posterior interosseous nerve
• Action
• Helps the triceps in extension of the elbow joint

26. Deep Layer
• There are five deep muscles
• Three deepextensorsof the forearm
• Function on thumb
• Abductor pollicis longus(APL)
• Extensor pollicis brevis (EPB)
• Extensor pollicis longus (EPL)
• To acquire insertion on the three bones of
thumb ‘crop out’
• From furrow in lateralelementof forearmbetweenlateral
andposterior groupsof superficial extensor
• One muscle
• Function onindex finger
• Extensor indicis
• In the upper part
• Supinator

27. Supinator
• Origin
• Lateral epicondyle of the humerus
• Annular ligament of the superior radio-ulnar joint
• Supinator fossa and crest of the ulna
• Insertion
• Upper 1/3rd of the lateral surface of shaft of radius
• Nerve Supply
• Posterior interosseous nerve
• Action
• Supination of the forearm
• At radio-ulnar joint

28. Abductor pollicis longus
• Origin
• Middle of the posterior surface of radius and ulna
• Interosseus membrane
• Insertion
• Posterior surface of the base of the 1st metacarpal
bone
• Nerve Supply
• Posterior interosseous nerve
• Action
• Abduction and extension of the thumb at
the carpo-metacarpal joint

29. Extensor pollicis brevis
• Origin
• Posterior surface of the shaft of radius
• Insertion
• Posterior surface of the base of the proximal
phalanx of the thumb
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension of the metacarpophalangeal joint of
the thumb

30. Extensor pollicis longus
• Origin
• Posterior surface of ulna
• Insertion
• Posterior surface of the base of the distal
phalanx of the thumb
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension of the interphalangeal joints of
the thumb

31. Extensor indicis
• Origin
• Posterior surface of ulna (below extensor
pollicis longus)
• Insertion
• Extensor expansion of the index finger.
• Nerve Supply
• Posterior interosseous nerve
• Action
• Extension of the interphalangeal joints of the
thumb

32. Wrist Drop
• Sign of radial nerve injury
• There are two common characteristic sites
of damage
• Axilla
• Injured viahumeral dislocationsor fractures of the
proximal humerus
• Radial groove of the humerus
• Injured via a humeral shaft fracture
• Radial nerve innervates
• All muscles in extensor compartment of
forearm
• In radial nerve lesion
• These muscles are paralysed
• Muscles that flex the wrist
• Innervated by median nerve
• Flexor muscles produces unopposed flexion at
the wrist joint – wrist drop