Faculty Of Medicine

Anatomy Department 1

Good morning

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• deep group of muscles of the back of forearm

a) Attachment

b) Action

c) N. supply

• Posterior interosseous nerve.

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radius ulna

Inter-osseous membrane

Olecranon

coronoid

Trochlear notch

Styloid process

head

neck tuberosity

Styloid process

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12 muscles

1. Supinator 2. Abductor pollicis

longus 3. Extensor pollicis

brevis 4. Extensor pollicis

longus 5. Extensor indices

1. Anconeus 2. Brachioradialis 3. Extensor carpi radialis

longus 4. Extensor carpi radialis

brevis 5. Extensor digitorum 6. Extensor digiti minimi 7. Extensor carpi ulnaris

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Muscles of back of forearm

Superficial

group (7)

Deep group

(5)

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4

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1. Brachioradialis

2. Extensor carpi radialis longus

3. Extensor carpi radialis brevis

4. Extensor digitorum

5. Extensor digiti minimi

6. Extensor carpi ulnaris

7. anconeus

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Abductor pollicis longus

Extensor pollicis brevis

supinator

Extensor pollicis longus

Extensor indices

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- 3 of the deep muscles:- 1. abductor pollicis longus, 2. extensor pollicis brevis, and 3. extensor pollicis longus- - Emerge from between tendons of : extensor digitorum & extensor carpi radialis brevis

- And pass into the thumb.

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All superficial muscles cross the elbow joint (arising from: Tip of lat. Epicondyle)

Deep muscles (except supinator) don’t cross the elbow Arise from: 2 bones of forearm & interosseous membrane & pass to: thumb and index

While

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o Anconeus o Brachioradialis o Extensor carpi radialis longus

Radial n.

• ECRB

• ED

• EDM

• ECU

• Supinator

• APL

• EPB

• EPL

• EI

Post. Interosseous n.

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For any muscle

origin

insertion

action

n. supply

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Ant. view Post. view

Lat. view

supinator

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Superficial head

1.lat. Epicondyle 2.Radial collateral lig. 3.Annular lig.

trochlea capitulum

ulna

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Supinator crest & fossa wide shallow depression at the lateral surface of ulna, distal to the tuberosity of ulna.

Deep head

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lateral surface of the radius (superior to: anterior oblique line & to insertion of pronator teres muscle)

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Supinator action:

Supinate extended forearm & hand

Supination

• Supination

(lat. Rotation forearm)

1- Thumb directed lateraly

2- palm faces anteriorly

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Muscles of supination

•In flexed forearm Biceps brachii

•In extended forearm

supinator

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Pronation

1-Thumb directed medially

2-Palm faces backwards

3- body of radius lies obliquely across ulna

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Med. Rotation forearm

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supination pronation

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pollicis longus

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1)Ulna (post. S.) 2)Radius (post. S.) 3)Interosseous membrane.

1st metacarpal bone (lat. Side of base)

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1)Abduct & 2)Extend thumb

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pollicis brevis

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1) Radius (post. S.) 2) Interosseous membrane

(post. S.)

proximal phalanx thumb (base, post. S.)

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Extension proximal phalanx thumb

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pollicis longus

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1) Ulna (post. S.) 2) Interosseous membrane

(post. S.)

Distal phalanx thumb (base, post. S.)

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Extension distal phalanx thumb

4. Extensor

indices

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1) Ulna (post. S.) 2) Interosseous membrane

(post. S.)

Extensor expansion Of index finger

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Assit extension all joints of index finger

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Tendon Extensor indices

Tendon of extensor digitorum

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radius ulna

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Radial nerve (C5,6,7,8 and T1) largest branch of the

brachial plexus. It is continuation of the posterior cord of the plexus

C 5

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8

T1

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Leave the axilla by passing in lower Triangular space to back of forearm

Run in spiral groove with brofunda brachii a.

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Pierce lat. Intermuscular septum To reach ant. Compartment again

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Run in groove bet. brachialis & brachioradialis , extensor carpi radialis longus

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TERMINATION: divides in front of the lateral epicondyle into superficial & deep terminal branches

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descends in the upper 2/3 of forearm under cover of the brachioradialis.

In the lower 1/3 of the forearm it passes posteriorly deep to tendon of brachioradialis to reach the dorsum of the hand .

Superficial terminal branch of radial n.

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Supply skin of the lateral 2/3 of the dorsum of the hand and the dorsal s. of the lateral 3 ½ fingers as far as the second phalanges.

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Deep terminal branch Posterior interosseous nerve

One of 2 terminal br. Of radial n.

Infront of lat. Epicondyle humerus

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● winds backwards passing between superficial and deep fibers of the supinator (piercing it) to reach the back of the forearm.

● In the back descends between the superficial and deep m. accompanied by: 1) the post. interosseous a. in the upper part. 2)terminal part of ant. interosseous a. in the lower 1/3 of the forearm

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BRANCHES OF THE POSTERIOR INTEROSSEOUS NERVE

Before piercing supinator

Inside supinator

After emerging From supinator

1.Extensor carpi radialis brevis

2.Supinaor

supinator

1.Extensor digitorum . 2.Extensor digiti minimi. 3.Extensor carpi ulnaris. 4.Abductor pollicis longus. 5. Extensor pollicis brevis. 6. Extensor pollicis longus. 7. Extensor indicis.

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N.B. Post. Interoseous n. supplies all muscles on Lat. side & dorsal S. of the forearm. except anconeus brachioradialis & extensor carpi radialis longus.

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The deep terminal branch with anterior interosseous a.

Passes deep to extensor retinaculum (in the 4th compartment) to the back of the carpus to supply joints .

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radius ulna

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1

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o Anconeus o Brachioradialis o Extensor carpi radialis longus

Radial n.

• ECRB • ED • EDM • ECU • Supinator • APL • EPB • EPL • EI

Post. Interosseous n.

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Test the radial nerve

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Thank you

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