Download MBBS Anatomy PPT 10 Extensor Forearm Bs Output Notes

Learning objectives

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? At end of this session, students should be able to:
? DESCRIBE
? Attachments, actions & innervations of ? groups of

muscles of posterior compartment of forearm

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? Contents of post compartment of forearm , their

anatomical Relations and clinical importance

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? Nerve of post compartment and applied anatomy.

Forearm
In general, muscles in the anterior
compartment of the forearm perform

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flexion at the wrist and fingers, and
pronation of forearm.
?anterior compartment, muscles are split

into three categories ?

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?superficial,
?intemediate &
?deep.

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Forearm
?Muscles of the forearm are mainly extrinsic

muscles of hand

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? are principle flexors and extensors of hand
? as well as pronators and supinators of

forearm.

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?Forearm is divided into two muscular

compartments;

?Anterior or flexor/pronator &

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?Posterior or extensor/supinator

compartments.

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? A crross-section of the forearm to show the muscular

compartments

Forearm Extensors - 3 functional groups

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Muscles - extend & abduct /adduct hand at wrist

extensor carpi radialis longus, extensor carpi radialis brevis

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& extensor carpi ulnaris

Muscles- extend medial four digits ? Ext

digitorum, ext indices & extensor digiti minimi

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Muscles - extend or abduct thumb

Abductor pollicis longus / brevis &

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extensor pollicis longus/brevis

Anconeus Supinator & Brachioradialis

Posterior facial compartment

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Superficial group
1. extensor carpi radialis brevis
2. extensor digitorum

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Common Extensor

3. extensor digiti minimi

Tendon

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4. extensor carpi ulnaris
5. anconeus

Deep group

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Supinator,

Lateral facial

abductor pollicis longus

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compartment

extensor pollicis brevis

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Brachioradialis

extensor pollicis longus

Exten. Carpi radialis

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extensor indices

longus
Posterior Compartment of Forearm

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? commonly known as extensor & supinator group

of muscles.

? general action - is extension at wrist & fingers

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? and supination of forearm.

? innervated by radial nerve.

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?Anatomically, muscles can be divided into two

layers;

?deep and superficial.

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?These two layers are separated by a layer of fascia.

Posterior compartment: 3 groups

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Superficial group 5
?

Extensor carpi radialis brevis Origin: Common Extensor

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?

Extensor digitorum

Origin , front of lateral

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?

Extensor digiti minimi

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epicondyle of Humerus.).

?

Extensor carpi ulnaris

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? Anconeus (posterior of lateral

epicondyle).

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Deep group 5 (3 to thumb+ 1

? Lateral group 2

to index + supinator).

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? Brachioradialis

? Supinator.

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? Extensor carpi radialis

? Abductor pollicis longus.

longus - (2 muscles

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? Extensor pollicis brevis.

originate from lateral

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? Extensor pollicis longus.

supracondylar ridge).

? Extensor indices.

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?Superficial

The superficial muscles in the anterior compartment are
the flexor carpi ulnaris, palmaris longus, flexor carpi

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radialis and pronator teres. They all originate from a
common tendon called the common flexor origin. This
arises from the medial epicondyle of the humerus.

?Intermediate

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The flexor digitorum superficialis is the only muscle of
the intermediate compartment. It can sometimes be
classed as a superficial muscle, but in most cadavers it
lies between the deep and superficial muscle layers.

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?Deep

There are three muscles in the deep anterior forearm;
flexor digitorum profundus, flexor pollicis longus, and

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pronator quadratus.

Superficial layer:
?contains seven muscles.

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?Four of these muscles ?

?extensor carpi radialis brevis ECRB,

?extensor digitorum ED,

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?extensor carpi ulnaris ECU

?extensor digiti minimi EDM

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? common tendinous origin fromlateral

epicondyle. common extensor origin

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? Muscles of the

Posterior/extensor

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Compartment of
the
forearm

Superficial group

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Common

Anconeus

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Extensor
Tendon

5

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1

4

2

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3

Superficial : 7 muscles

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lateral to medial -

? Brachioradialis.
? Extensor carpi radialis

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longus, (ECRL).

? Extensor carpi radialis

brevis, (ECRB).

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? Extensor digitorum.
? Extensor digiti minimi .
? Extensor carpi ulnaris.
? Anconeus (An).

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Superficial extensor
? Arises - common extensor

origin, front of lateral

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epicondyle of humerus,
Except, 2 (BR & ECRL).

? All cross wrist Except, 1

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brachioradialis.

? All supplied - deep branch

of radial nerve, Except ABE

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? Anconeus
? Brachioradialis
? Extensor carpi radialis

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longus

? These 3 by radial nerve .

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? Brachioradialis
? Origin:

? Lateral supracondylar

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ridge of humerus

? Insertion:

? Base of styloid process

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of radius

? Action:

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? Flexes forearm;

(elbow).

? Rotates forearm to

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midprone position

? Extensor Carpi

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radialis longus

? Origin: Lateral

supracondylar

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ridge of humerus

? Insertion:

? Posterior surface

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of base of
second
metacarpal bone

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? Action:

?

Extends and

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abducts hand at
wrist joint

Extensor carpi radialis

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brevis: base of 3rd
metacarpal bone.
Extensor digitorum:
Extensor expansion of
medial 4 fingers.

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Extensor digiti minimi:
Extensor expansion of
little finger.
Extensor carpi ulnaris:
Base of 5th metacarpal

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bone.

?Brachioradialis is a paradoxical

muscle.

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?Origin and innervation are

characteristic of a extensor muscle,

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?But it is actually a flexor at elbow.

?Muscle is most visible when forearm

is half pronated, and flexing at the

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elbow against resistance.


Deep Muscles ? five muscles
? supinator,

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?abductor pollicis longus,

?extensor pollicis brevis,

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?extensor pollicis longus

?extensor indicis.

?all these muscles act on thumb and the index

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finger.

?exception of supinator.

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II- Deep group: 5 muscles

? Abductor pollicis longus,

(APL).

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? Extensor pollicis brevis,

(EPB).

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? Extensor pollicis longus,

(EPL).

? Extensor indicis (EI).

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? Supinator.
All back muscles of forearm
are supplied by posterior
interosseous nerve except ,

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ABE by Radial nerve.

Dorsal Extensor Expansion

It is formed by union of tendons :

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Extensor digitorum, Extensor indicis, Extensor
digiti minimi, palmar, dorsal interossei &
lumbricals muscles.
? All these tendons unite to form one

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tendon which divides into 3 slips,

? median one attached to middle phalanges

&

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? 2 lateral attached to terminal phalanges.

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Dorsal Extensor Expansion

Deep group

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extensor indices

Lateral Compartment

Arteries of Posterior Compartment

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Nerves of Posterior

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Compartment

Synovial tendon

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sheath

5

2

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6

4

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3

1

Extensor retinaculum

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Extensor retinaculum

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Posterior interosseous nerve syndrome
weakness or paralysis of the wrist and digital extensors.
Pain may be present, but it usually is not a primary
symptom. Attempts at active wrist extension often result
in weak dorsoradial deviation as a consequence of

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preservation of the radial wrist extensors but
involvement of the extensor carpi ulnaris and extensor
digitorum communis.
These patients do not have a sensory deficit.
Rarely, compression of the posterior interosseous nerve

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may occur after bifurcation into medial and lateral
branches.
?Clinical correlates

1. Brachial Pulse and Blood Pressure: The brachial

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pulse palpation and measuring blood pressure can be
done immediately medial to the biceps tendon in the
cubital fossa. The stethoscope must be placed there,
to hear the korotkoff sounds.

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2. Venipuncture

The median cubital vein is located superficially within
the roof of the cubital fossa. It connects the basilic
and cephalic veins, and can be accessed easily ? this

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makes it a common site for venipuncture.