anatomy - upper limb - 3 muscles, innervation and compartments of the upper limb

8/16/2019 Anatomy - UPPER LIMB - 3 Muscles, Innervation and Compartments of the Upper Limb

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Muscles, Innervation and the Compartments of the Upper LimbOrganized in an Unintentionally Difficult M anner

Fascia and compartments of the shoulder

PECTORALIS FASCIA- The only contents is Pectoralis Major ;- Pectoralis fascia continue inferiorly as fascia of the anterior abdominal wall - It continues laterally-once it leaves the lateral edge of Pectoralis Major, it becomes AXILLARY FASCIA

AXILLARY FASCIA- Continuous with the CLAVIPECTORAL FASCIA - Forms the floor of the axilla

CLAVIPECTORAL FASCIA - Deep to the Pectoralis major muscle, the CLAVIPECTORAL FASCIA invests the subclavius muscle and pectoralis minor . - It forms the costocoracoid membrane above pectoralis minor, and the suspensory ligament of axilla below pector

minor. The suspensory ligament drags the axillary fascia upwards when the arm is raised, forming the actual “pit” of the armpit

Supraspinous, Infraspinous and Subscapular fascia- The supraspinatus , infraspinatus and subscapularis muscles are contained in their own little fascial compartments

Deltoid Fascia- The deltoid has its own fascia, continous with the pectoral fascia and infraspinatus fascia - It has numerous fascial septa which separate the fascicles of the deltoid

Clavicle

Subclavius

Axi ll ary fascia

Costocoracoid membrane

Axi ll ary fascia

Pectoralis minor

Suspensory li gament of axi ll a

Lateral pectoral nerve

Pectoral is major, wrapup in pectorali s fasci

Supraspinatusfascia

Subscapularisfascia

I nfr aspinatus fascia

Spine of scapul a

Clavicle

Pectoral is fas

Deltoid fascia

I nfr aspinatus fascia

F ascial septa

Pectoralis fascia, infraspinatus fascia and deltoid fascia all continue down the arm to form the brachial fascia

and Thoracoacromial artery


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Anterior Axioappendicular Muscles of the ShoulderThere are 3 distinct groups of shoulder muscles:

ANTERIOR AXIOAPPENDICULAR MUSCLES – 4 muscles which move the pectoral girdlePOSTERIOR AXIOAPPENDICULAR MUSCLES – 4 muscles which attach the upper lumb to the skeleton of the tSCAPULOHUMERAL MUSCLES – 6 muscles which act on the glenohumeral joint

Anterior Axioappendicular musclesAll supplied by stupidly different nerves.No pattern whatsoever.

Pectoralis Major Two heads:

- CLAVICULAR HEAD: lateral pectoral nerve o Originates from the medial half of the anterio

clavicle - STERNOCOSTAL HEAD: medial pectoral nerve

o Originates from the anterior surface of the sternumand the first 6 costoclavicular cartilages

o Also originates from the aponeurosis of the externaoblique muscle of the abdomen

- INSERTS INTO THE LATERAL LIP OF THE INTERTUBEGROOVE OF THE HUMERUS

- Its inferior border forms the anterior axillary fold o Abducts and medially rotates the humerus o Draws scapula anteriorly and inferiorly by

pulling on the humerus - The heads can act independently:

o Clavicular head alone acts to flex the humeruso When flexed, the sternocostal head extends it

from its flexed position.

Pectoralis Minor medial pectoral nerve - Originates at the 3 rd, 4th and 5 th ribs near the costal

cartilages - Inserts into the medial border and superior surface of th

coracoid process of scapula - Its job is to stabilize the scapula by pulling it anteriorlyand inferiorly against the chest wall

- It also assists in elevating the ribs when breathing - All the vessels and nerves to the arm travel under the

pectoralis minor.

Subclavius nerve to subclavius - Originates at the junction of the 1 st rib and its costal cartilage- Inserts into the “groove for subclavius” on the inferior surface

of the middle third of the clavicle- Depresses and anchors the clavicle- Protects the subclavian vessels when the clavicle is fractured

Serratus anterior long thoracic nerve - Originates from the lateral surfaces of the first 8 ribs- Inserts into the medial border of scapula- Protracts the scapula, holds it against the chest wall, and

rotates it superiorly (eg when reaching for something up high)THE MAIN PROTRACTOR OF THE SCAPULA

- One of the most powerful muscles in the pectoral girdle.- Its paralysis causes a winged scapula. Also, the arm cannot be

abducted past the horizontal position (the scapula doesn’trotate upwards anymore)

- If you insert your chest drain BELOW the mid-axillary line, ywill cause this sort of paralysis, which is embarrassing.

Innervation

Pectoralis M ajor :clavicular head

Pectorali s major:stern ocostal head

I ntertubercular grooveof the humerus

Pectoralis M inor Subclavius

Serr atus An terior

Long Th oracic Nerve:Off the roots of C5, 6 and 7Serratus Anterior

Nerve to Subclavius:Off the superior trunkSubclavius

M edial Pectoral nerve: Branch of the medial cordPectoralis Minor; sternocostal head of Pectoralis Ma or

Lateral Pectoral nerve: Branch of the lateral cordclavicular head ofPectoralis Major


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Posterior Axioappendicular Muscles of the Shoulder: the Extrinsic GroupThere are 2 layers, the superficial and the deep.The superficial group is trapezius and latissimus dorsiThe deep group is the levator scapulae and the rhomboids

Posterior Axioappendicular Extrinsic MusclesAlso supplied by confusingly different nerves.

Trapezius spinal accessory nerve - Originates from

o The external occipital protuberance o Nuchal ligament o Medial third of superior nuchal line o Spinous processes of C spine and T-spine o he medial half of the anterior clavicle

- Inserts into :o Lateral third of the clavicle o Acromion of scapula o Spine of scapula

- Has 3 distinct parts: SUPERIOR (descending)part which ele

the scapula MIDDLE part which retracts the scapul INFERIOR (ascending) part which

depresses the scapula All the parts together act to rotate the scapula superiorly, sothe glenoid fossa faces up.

Latissimus dorsi Thoracodorsal nerve - Originates from

o Inferior 6 thoracic vertebraeo Thoracolumbar fasciao Iliac cresto Inferior 3 or 4 ribs

- Inserts into the ANTERIOR surface of the humerus, at the floof the intertubrercular groove

- Extends, adducts, medially rotates the humerus - Lifts the body up too the arms when climbing

Levator scapulae dorsal scapular and cervical nerv- Originates at the posterior tubercles of the spinous processes

of the C1, 2, 3 and 4 vertebrae- Inserts into the medial border of scapula, superior to the spine- Elevates that corner of the scapula, rotating it so the glenoid

cavity faces down- Extends the neck (when acting bilaterally) or flexes it laterall

(when acting unilaterally)

Rhomboid Minor dorsal scapular nerve - Originates from the nuchal ligament and the spinous processe

of C7 and T1- Inserts into the medial border of the scapula, at the root of the

scapular spine- Retracts the scapula

- Rotates the scapula so the glenoid cavity faces down- Fixes the scapula to the thoracic wall

Rhomboid Major dorsal scapular nerve - Originates from the spinous processes of T2,3 4and 5- Inserts into the medial border of the scapula, from the root of

spine down.- Retracts the scapula- Rotates the scapula so the glenoid cavity faces down- Fixes the scapula to the thoracic wall

Viewed from above

Fl oor of the intertuberculargroove, anterior ly on th ehumerus

Superi or part ofTrapesius

M iddle part ofTrapesius

M iddle part ofTrapesius

T7

Lati ssimus dorsi

Innervation

Levator scapulae

Rhomboid Mi nor

Rhomboid M ajor

Dor sal scapular nerve:Off the roots of C5Rhomboid major and minorLevator sca ulae

Thor acodorsal Nerve:Off the posterior cordLatissimus dorsi


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Posterior Axioappendicular Muscles of the Shoulder: the Intrinsic Group with Rotator Cuff musclesThese are the deltoid and teres major; and the 4 rotator cuff muscles (teres minor, supraspinatus, infraspinatus and subscapularis)

Posterior Axioappendicular Intrinsic musclAgain, supplied by totally different nerves.

Deltoid axillary nerve - Originates from the lateral third of the clavicle, the

acromion, and the lateral spine of scapula . - Inserts into the deltoid tuberosity of humerus- THREE PARTS:

o Anterior part flexes and medially rotates thehumerus

o Middle part abducts the humeruso Posterior part extends and laterally rotates the

armo The middle part is multipennate; the others are

unipennate - It cannot initiate abduction on its own when the arm is fu

adducted- thus it needs supraspinatus to initiate the movebecomes effective after about 15 degrees of abduction.

- The deltoid’s anterior and posterior parts swing your armwalking.it also helps to keep the humeral head in the glen

fossa.

Teres major lower subscapular nerve - Originates from the posterior surface of the inferior

angle of scapula- Inserts into the medial lip of the intertubercular gro

of humerus- Adducts and medially rotates the arm- Also keeps the head of humerus in the socket

Rotator Cuff MusclesWhatever other actions they may have, they all helthe humeral head in the glenoid fossa Supraspinatus suprascapular nerve

- Originates in the supraspinous fossa of the scapula- Inserts into the superior facet of the greater tubercle of

humerus- Initiates abduction, and assists the deltoid with abduction

the arm; its the only one that doesn't rotate the arm.

Infraspinatus suprascapular nerve - Originates in the infraspinous fossa of the scapula- Inserts into the middle facet of the greater tubercle of

humerus- Laterally rotates the arm

Teres Minor axillary nerve - Originates from the middle of the lateral border of scapul- Inserts into the inferior facet of the greater tubercle of

humerus- Laterally rotates the arm

Subscapularis upper and lower subscapular ner- Originates in the subscapular fossa- Inserts into the lesser tubercle of humerus- Medially rotates and abducts the arm

Innervation

Deltoid

Supraspinatus

Subscapularis

Teres M ajor

I insertion of deltoid, at theDeltoid Tu berosity

I nfr aspinatus

Teres Mi nor

Deltoid

Supraspinatus

Subscapularis

Deltoid

I nfr aspinatus

Teres M ajor Teres M inor

Teres M ajor

Axil lary nerve:Off the posterior cordTeres MinorDeltoid

Upper Subscapul ar nerve

SubscapularisLower Subscapular nerve

SubscapularisTeres major

Suprascapular nerve

SupraspinatusInfraspinatus


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Muscles and Nerves involved in the movements of the shoulder jointflexion:

pectoralis major (clavicular head) – medial and lateral pectoral nervedeltoid (anterior part) – axillary nerve coracobrachialis – musculocutaneous nerve biceps femoris – musculocutaneous nerve

extension:deltoid (posterior part) – axillary nerve teres major – lower subscapular nerve

abduction:deltoid (central part) – axillary nerve supraspinatus – suprascapular nerve

adduction:pectoralis major – medial and lateral pectoral nerve latissimus dorsi – thoracodorsal nerve subscapularis - upper and lower subscapular nerve infraspinatus – suprascapular nerve teres minor – axillary nerve

medial rotation:subscapularispectoralis major –medial and lateral pectoral nerve deltoid (anterior part) – axillary nerve latissimus dorsi – thoracodorsal nerve

lateral rotation:infraspinatus – suprascapular nerve

long head of triceps – radial nerve coracobrachialis – musculocutaneous nerve short head of biceps – musculocutaneous nerve


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Fascia and compartments of the proximal arm

Posterior Compartment: EXTENSORS- Triceps Brachii- Anconeus- Radial nerve - Deep artery of the arm (profunda brachii)

(A branch of the brachial artery)- Superior ulnar collateral artery - Ulnar nerve as depicted here is in the posterior

compartment; it travels anteriorly to the medial intermuscularseptum, until it pierces it about half-way down the humerus,together with the superior ulnar collateral artery

Anterior Compartment: FLEXORS- Biceps Brachii - Brachialis - Coracobrachialis - Median nerve - Musculocutaneous nerve

The medial cutaneous nerve of forearm is not insidethe fascial sheath, but is still important enough to warrant a

brief mention.- The Basilic vein and the Cephalic vein areusually superficial to the fascial planes

.

Brachial Fascia- Encloses the upper arm like a sleeve - Superiorly, it is continuous with the deltoid fascia,

infraspinatus fascia and pectoralis fascia - Inferiorly, it is attached to the epicondyles of the

humerus and the olecranon of ulna - It is continuous with the antebrachial fascia – thefascia of the forearm

o It contains two SEPTA: the MEDIAL andLATERAL INTERMUSCULAR SEPTA.

o The septa are attached to the supracondylarridges and to the shaft of humerus

o They separate the arm into theANTERIOR COMPARTMENT and thePOSTERIOR COMPARTMENT

Section at a level just shor t of half -way along the humeri s

Anteri or compartment

Posterior compartment

M edial intermuscular septum

Lateral i ntermuscular septum

Deltoid: Not actually a part of the anteriorcompartment, as it has its ownascial compartment.

Lateralintermuscularseptum

Cephali c vein Bi ceps brachii

Tr iceps brachii

M usculocutaneous nerve

M edian nerve

Basil ic vein

Br achial artery

Coracobrachialis

Brachialis

Medialintermuscularseptum

Supplied by theMUSCULOCUTANEOUSNERVE

Ul nar nerve

Radial n erve

Superior ul nar collateral artery

Deep artery of th e armLateral in termuscular septum

Supplied by theRADIAL NERVE

M edial intermuscular septum

M edial cutan eousnerve of f orearm


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The innervation and mechanics of the flexor and extensor muscle compartments of the armAnterior Compartment: FLEXORSAll supplied by the MUSCULOCUTANEOUS N

Biceps Brachii Two heads:

- SHORT HEAD: o The medial head.o Originates from the tip of the coracoid process

- LONG HEAD: o The lateral head. o Originates from the supraglenoid tubercle of the

glenoid fossa - The biceps inserts into the tuberosity of radius; and it also in

into the antebrachial fascia by virtue of the bicipital aponeur- It does very different things depending on what position the

arm is in: o It supinates the forearm by pulling on the

aponeurosis, when the arm is pronated; it is theMOST POWERFUL SUPINATOR of the forearm

o when the forearm is supine if FLEXES the elbowby pulling on the attachment to the radial tuberosi

o It is useless as a flexor when the forearm is pronat

- The short head resists dislocation of the shoulder

Coracobrachialis - Originates at the tip of the coracoid process of scapula - Inserts into the middle third of the medial humerus - Helps flex and adduct the arm - Resists dislocation of the shoulder: it’s a SHUNT muscle, it

resists the downward dislocation of the humeral head - Stabilizes the glenohumeral goint - A landmark – it is pierced by the musculocutaneous nerve

Brachialis - Originates from the distal half of the anterior humerus - Inserts into the tuberosity of the ulna, and the coronoid proce

- Flexes the forearm in all positions – it’s the PRIMARY FL

Posterior Compartment: EXTENSORSAll supplied by the RADIAL NERVETriceps Brachii

- LONG HEAD: o Originates from the infraglenoid tubercle

- LATERAL HEAD: o Originates from the proximal humerus, more

proximal than the radial groove - MEDIAL HEAD:

o Originates from the posterior surface of the humedistal to the radial groove

The united triceps inserts into the olecranon of ulnaIt is the chief extensor of the arm.The long head resists dislocation of the head of humerus,especially during abduction

Anconeus- Originates from the posterior lateral epicondyle of humerus- Inserts into the lateral surface of olecranon - Assists the triceps in flexing the forearm, and stabilizes the

elbow joint. It also pulls the joint capsule out of the way of tholecranon upon extension; otherwise it would get pinched inthe olecranon fossa . Many anatomists believe it to be a vesand forgotten 4th head of the triceps.

CoracobrachialisTi p of the coracoidprocess

Transversehumeralligament

Supraglenoi d tubercl e

Bi ceps Br achii

Brachialis

Short head

L ong head

Bi cipital aponeurosis

Coronoid pr ocess andthe tuberosity of ul na

Tuberosity of radius

L ong head of tr iceps

M edial head of tr iceps

Lateral headof tr iceps

Anconeus

I nfr aglenoid tubercle

Some of the brachialis isinnervated by the radial nerve-the half that is posterior to theinsertion of deltoid


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Fascia and compartments of the distal armSection at the junction of di stal thi rd and proximal two thi rds of the humeru s

Section at the level of the humeral epicondylesSuperi or ul nar coll ateral ar tery

Ul nar nerve

Deep artery of th e arm

Radial n erve

Tr iceps brachii

Longhead

MedialheadLateral

head

Cephalic veinBiceps brachii

M usculocutaneous nerve

M edian nerve

Basil ic vein

Br achial arteryCoracobrachialis

M edial cutaneous nerveof forearm which arises

from the MEDIAL CORD o

brachial plexus

Posterior cutaneous nerve offorearm which has just branched off

from the RADIAL nerve

L ateral cutaneous nerve offorearm which has just branched off

from the MUSCULOCUTANEOUS nerve

Brachialis

Brachialis

Bi ceps brachii

Basil ic vein

Cephali c vein

Radial nerve which has pierced thelateral intermuscular septum a little whileago, and now travels between brachialisand brachioradialis

Br achial artery

M edian nerve

Ul nar nerve

Tr iceps Brachii tendonAnconeusWhich is unimportant, and arguably useless. In fact some anatomists believe it to a rudimentary 4thtriceps head. If it were missing, you would likely not notice.

Brachioradialiswhich is important for

a number of reasons:- Forms the lateral borderof the cubital fossa

- Innervated by the RADIAL NERVE - Flexes the forearm, unlike

the rest of the forearm extensorcompartment

- Together with the Supinator, theyare the only extensor compartmentmuscles which do not cross the wristand cause no movement there

PRONATOR TERES


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Fascia and compartments around the cubital fossa and distal forearm

Antebrachial Fascia- Extension of the brachial fascia - Also envelops the forearm like a sleeve - There are no “intermuscular” septa per se; the

muscles are all invested in their own fascia;however there are still two recogniseablecompartments: the FLEXOR compartment andthe EXTENSOR compartment.

Section at the level of the neck of radiusBasil ic vein

Cephali c vein

In 20% of people, the basilic vein branches off in“median basilic” vein, and when it joins the medicephalic vein they form a clear “M”.

M edian cubital vein

Cephali c veinM edian antebrachial vein

Basil ic vein

H ighl y variable tri butaries

Neck ofRadius

ULNA

COMPARTMENTS IN THIS SECTIONare not clear-cut or sensible.- This is an intersection of several compartments. The EXTENSOR compartment of the forearm is anterolateral, represented by

brachioradialis, extensor carpi radialis longus and brevis, and extensor digitorum. The FLEXOR compartment is posteromedial andrepresented by pronator teres, palmaris longus, flexor carpi ulnaris, and flexor digitorum profundus and superficialis. The ANTERIORcompartment of the arm is represented by the biceps tendon, and by brachialis.

- Anconeus is a lonely representative of the POSTERIOR compartment.

The BICEPS TEND ON: one part blends with the antebrachial fascia; The other part dives deep to attach to the radial tuberosity

Br achial artery which bifurcates at the levof the radial head in the cubital fossa

Pron ator teres which originates proximallthe medial epicondyle, and forms the medial borof the cubital fossa

The F lexors of the forearm which orat the Common Flexor origin, at the medialepicondyle of the humerus

BrachioradialisWhich forms the lateralborder of the cubital fossa

Brachialis

Brachialis

Bi ceps tendon

Extensor Car pi Radiali sL ongus and Brevis

Extensor Digitorum

Anconeus

Brachioradialis

Radial artery Uln ar artery

Daughters of the recentlybifurcated Brachial Artery

BrR

ECRL, B

ED

Superf icial branch of theradial nerve which travelsunder brachioradialis down thearm, where it supplies sensationto the dorsum of the hand

Deep branch of the Radial N erve whichwill pierce the Supinator, penetrate theinterosseous membrane and become the

Posterior Interosseous Nerve

The branches of the Radial Nerve

M edian nerve which travels between the heads of P. teresPron ator Teres

Palmaris Longus

Annul ar Li gament

Fl exor Carpi Ulnaris which is finn ervated by the ul nar nerve, unlirest of the flexors

Fl exor Digitorum Superf icialis(humeral head)

Fl exor Carpi Radialis

Fl exor Di gitorum Profu ndisH alf of w hich i s in nervated by the ulnar n erve, unlike the reof the flexors (which are all supplied by the Median nerve)

Ul nar n erve, which runs between the twoheads of flexor carpii ulnaris

THERE ARE 17 MUSCLES CROSSING THE ELBOW JOINT.


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Fascia and compartments of the middle forearm

Boun dari es of the compartments:

Section at the level of the mid-forearm

FL EXOR COM PARTM ENTTh is is the beefier compar tment; twi ce as fat as the extensor compartment

4 l ayers of muscles:

EXTENSOR COMPARTMENT

M edial border: subcutaneous ul na

I nterosseous membrane

L ateral border: radial ar tery

Fl exor carpi radialis

Flexordigitorumsuperficialis

M edian nerve

Palmaris Longus

Fl exor carpi uln aris( uln ar nerve)

Fl exor Polli cisLongus

Flexor

digitorumprofundus

AnteriorI nterosseousArter

Anterior I nterosseous Nerve Uln ar Nerve

Ulnar Ar tery M edial cutaneous nerve of f orearm

LA YER 1: pronator teres(not shown, too proximal) F lexor carpi radialisPalmari s longus

F lexor carpi ulnaris LA YER 2: Flexor digitorum

superficialis

LA YER 3:F lexor pollicis longusF lexor digitorumprofundis

LA YER 4: Pronator Quadratus(not shown, too distal)

Brachioradialis

Radial artery

Superf icial br anch of the radial nerve

Extensor poll icis Br evis

Extensor carpiradiali s brevis

L ateral cutaneousnerve of the forearm

Extensor carpiradiali s longus Supinator

Extensor digitoru m

Abductor poll icis longus

Extensor polli cis Longus

Extensor carpi u lnari s

Extensor indi ces

Posterior in terosseous nerve

Posterior in terosseous artery

Half of the Flexor Digitorum Profundus which isinn ervated by the ulnar nerve, unlike the rest of the

flexors (which are all supplied by the Median nerve

Muscles of a similar purpose are

grouped together in compartments.The EXTENSORS are posteromedial, anthe FLEXORS are anterolateral. Theyspiral round the arm and eventually theflexors become truly anterior and theextensors become truly posterior.

- Functionally, the forearm includes thedistal humerus because the muscles thatattach at the supracondylar ridges andthe epicondyles stretch along theforearm to move the wrist and fingers.

BOUNDARIES OF THE COMPARTME

POSTERIORLY (proximal forearm) andMEDIALLY (distal forearm), thesubcutaneous border of the ulna

ANTERIORLY (proximal forearm) athen LATERALLY (distal forearm),the radial artery

Because neither of these boundariesis crossed by motor nerves they areused for surgical incisions

The border between l ayers 1-2 and l ayers 3-4 is the pri maryneurovascular plane of the anterior compartment: theneurovascular bundles exclusive to this compartment travel within it


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The Flexor Compartment of the ForearmThe flexor compartmenthas 4 discrete layers:LAYER 1:All of these, except the ulnar head of pronator quadratus, attach to the medial humeral epicondyle at theCOMMON FLEXOR ORIGIN

- PRONATOR TERES o Forms the medial border of the cubital fossa; it’s the most lateral of the first layer of muscles o Has an ulnar head and a humeral heado The humeral head originates from the COMMON FLEXOR ORIGINo The ulnar head originates from the coronoid processo Pronates and flexes the elbow

- FLEXOR CARPI RADIALIS o Originates from the COMMON FLEXOR ORIGINo Inserts into the base of the 2nd metacarpalo Flexes and abducts the wristo About half-way down the forearm, its belly is replaced

by a flat tendon which becomes cord-like at the wristo It travels in the lateral carpal tunnel inside its own

synovial sheath (it doesn’t share) o The radial artery is just lateral to this tendon

- PALMARIS LONGUS o Originates from the COMMON FLEXOR ORIGINo Inserts into the distal flexor retinaculum, and palmar aponeurosis.o Flexes and abducts the wrist, tenses the palmar aponeurosiso Its actually absent in 14% of people (usually on the left side). Those people don’t miss it being gono The tendon of palmaris longus is a marker for where the median nerve is – the tendon passes med

to it, and then deep to it in the flexor retinaculum

- FLEXOR CARPI ULNARIS o Has an ulnar and a humeral heado Humeral head originates from the COMMON FLEXOR ORIGIN; Ulnar head originates from t

olecranon, and posterior border of ulnao Inserts into the pisiform, hook of hamate and the 5th metacarpal.o Flexes and abducts the wrist; has its own synovial sheatho The tendon of flexor carpi ulnaris is a marker for the ulnar artery, which passes laterally to it a

LAYER 2 - FLEXOR DIGITORUM SUPERFICIALIS

o The fast flexor of the fingers. Has two heads: humeroulnar head and radial heado The humeroulnar head originates from BOTH the COMMON FLEXOR ORIGIN and the coro

of ulna; the radial head originates the proximal half of the radiuso It inserts into shafts of the middle phalangeso It flexes the metacarpophalangeal joints and the proximal interphalangeal joints;it can flex each jo

independently of the others. o Its tendons are enclosed in the COMMON FLEXOR SHEATH together with the tendons of fle

digitorum profundus

LAYER 3- FLEXOR DIGITORUM PROFUNDUS

o The slow flexor of the fingerso Originates from the interosseous membrane, and from the proximal three quarters of the anteri

of the ulna. It has two parts: medial and lateral parts;o The medial part is innervated by the ulnar nerveo The medial part flexes the distal interphalangeal joints of the 4th and 5th digitso The lateral part flexes the distal interphalangeal joints of the 2nd and 3rd digitso All parts can flex the wrist joint as well as the fingerso The lateral part is innervated by the ANTERIOR INTEROSSEOUS NERVE (a branch of the m

nerve).o The tendon to the index finger tends to separate early; it’s the only one which can operate indepe

Unlike the flexor digitorum superficialis, the profundus flexes all the DIPs together.

- FLEXOR POLLICIS LONGUSo Originates from the anterior surface of the radius and the nearby interosseous membraneo Inserts into the base of the distal phalanx of thumb. It has its own synovial sheal in the carpal tuo Also innervated by the ANTERIOR INTEROSSEOUS NERVEo It flexes the phalanges of the thumb; mainly the distal interphalangeal joint (it’s the only muscle th

flexes the DIP of the thumb)

LAYER 4- PRONATOR QUADRATUS

o It originates from the distal quarter of the ulna, and inserts into the distal quarter of the radiuso It is innervated by the ANTERIOR INTEROSSEOUS NERVEo It pronates the forearm (it’s the PRIMARY PRONATOR of the forearm) and its fibers hold the r

ulna together. When speed is needed, it is assisted by the Pronator Teres.

All supplied by the MEDIAN NERVE,…except:Flexor Digitorum Profundis, ulnar halfFlexor Carpi Ulnaris, whole

Ulnar nerve

Ulnar nerve

Median nerve: mainly Layers 1 and 2 - Pronator teres- Flexor carpi radialis- Palmaris longus- Flexor digitorum superficialis

Anterior Interosseous nerve: mainly layer- Flexor digitorum profundus, l- Flexor pollicis longus- Pronator quadratus

Ulnar nerve:- flexor digitorum profundus, m- flexor carpi ulnaris

Pronator teres Humeral headUlnar head ishidden, but itoriginates fromthe coronoid

process

COMMON FLEXOR ORIGIN: Pronator teres, humeral head Flexor carpi radialis Palmaris longus Flexor carpi ulnaris, humeral head Flexor digitorum superficialis,

humeral head

Flexor carpiradialisThe belly isreplaced bya flat tendonwhichbecomescord- like atthe wrist

Palmaris Longus

Flexor carpi Ulnari sTwo heads, one originating

from the humerus, theother from the olecranon

Inserts into thePisiformHook of h amateBase of the 5 th metacarp al

Median nerve Lateral to the palmarislongus tendon

RadialArtery

Lateral to the flexor carpiradialistendon

Flexor digitorum superficialis Humeroulnar head(common flexor origin and thecoronoid process)Radial h ead

Fl exor polli cis longus

Flexor digitorumprofundus:

Supplied byMEDIAN NERVEULNAR NERVE

Pronator Quadratus

The flexors digi torum prof undus andsuperf icial is are WEA KE R when the

wrist is flexed, the tendons aren’t tense


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Extensor Compartment of the Forearm: Superficial layerSUPERFICIAL LAYER OF EXTENSORStwo originate from the supracondylar ridge as well as the adjaintermuscular septum:

Brachioradialiso radial nerve o Inserts at the lateral surface of the distal end of the radiuso Flexes the forearm, in a feeble way, and mostly when the

is pronated; it also acts as a shunt muscle to prevent subluof the head of radius. its most active in quick movements,movement against resistance.

o Forms the lateral border of the cubital fossao under it run the radial nerve and the radial arteryo Distally, its tendon is covered by the tendons of Abductor

Longus and Extensor Pollicis Brevis.

Extensor Carpi Radialis Longuso radial nerve o Inserts at the dorsum of the2nd metacarpal, at the baseo extends and abducts the hand at the wristo probably more involved in abduction than the ECRBo it is crucial in the clenching of the closed fist.

Four originate from the common extensor origin, at the lateepicondyle of the humerus

Extensor Carpi Radialis Breviso deep branch of radial nerve o

Inserts into the dorsum of the3rd metacarpal at the baseo extends and abducts the hand at the wristo it is covered by the Extensor Carpi Radialis Longuso They also share the same extensor tendon sheath at the wro the brevis is more involved in extension than the longus

Extensor Digitorumo posterior interosseous nerve which is really the continua

the deep branch of the radial nerve o inserts at the extensor expansions of the fingerso THE EXTENSOR EXPANSIONSare triangular aponeurose

which wrap around the metacarpal head, and the proximaphalanx. They are united with the insertions of the lumbrthe interosseous muscles.

o The tendons thus divide into a median band which passesbase of the middle phalanx, and two lateral bands which ithe base of the distal phalanx.

o

Extends the fingers, primarily at the metacarpophalangealsecondarily at the distal interphalangeal joint.o Occupies a lot of space in the extensor compartmento Shares an extensor tendon sheath with the Extensor Indicio Just proximally to the metacarpophalangeal joints, the

tendons are linked by intertendinous connections whichprevent the fingers from being independently extended; thyou can never fully extend a finger while the others remaiflexed. This is most true of the ring finger.

Extensor Digiti Minimio posterior interosseous nerveo Divides into two tendons- the lateral one joins the pinky t

the extensor digitorum, and then together with the medial three insert into theextensor expansion of the pinky fing

o extends the pinky, primarily at the metacarpophalangeal jsecondarily at the distal interphalangeal joint.

o this is really just a detached part of the extensor digitorumo However, it has its own tendon sheath

Extensor Carpi Ulnariso posterior interosseous nerveo yes it does originate at the common extensor origin; thats

humeral head. There is also an ulnar head, which originatulnar border posteriorly, via an aponeurosis. This origin isshared with the Flexor Digitorum profundis and the FlexoUlnaris.

o inserts at the dorsum of the base of 5th metacarpalo extends the hand at the wrist joint, and abducts ito It has its own tendinous sheath at the wristo It is also crucial to the formation of the closed fist

All extend the forearm, wrist or fingers – EXCEPT BRACHIORADIALISBr achioradiali s is the soli tary exception:it is in the extensor compartment, but it flexes the forearm.

It is the only fl exor innervated by the radial nerve.

All supplied by the RADIAL NERVE,or some branch thereoftwo la ers: the SUPERFICIAL and DEEP

Brachioradialis

Ext ensor CarpiRadiali s Longus

Extensor CarpiRadiali s Brevis whichlies under the ExtensorCarpi Radialis Longus

Br achioradial is tendonwhich lies underthe tendons of

Abductor Pollicis Longusand Extensor Pollicis Brevis

Common extensor origi n

The I nserti ons of the ExtensorsCarpi Radial is tendons:

Bases of the metacarpals Longus inserts into the 2 nd Brevis inserts into the 3rd

The common tendonsheath of th extensorscarpi radialis: both travelwithin the same sheath

Extensor Carpi Uln aris

Extensor Digiti Mi nimi

The Tendon of Ex tensorDigit Minimi divides intotwo tendons; the lateralone joins the extensordigitorum tendon to thelittle finger

Extensor D igitorumThe fattest muscle here

Tendon sheaths: Extensor carpi ulnarishas its own; and sodoes extensor digitiminimi. The extensordigitorum shares a

sheath with the tendonof Extensor I ndicis

I ntertendinous connections whichunite the extensor digitorumtendons and prevent the digits fromextending independently


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Extensor Compartment of the Forearm: Deep layer

DEEP LAYER OF EXTENSORS"true" deep layer

Supinatoro deep branch of radial nerve which pierces it on it

to transforming into the posterior interosseous nero originates from everywhere... the lateral humeral

epicondyle, the radial collateral ligament, the annuligament, the supinator fossa and the crest of ulna

o inserts into the lateral posterior and anterior surfacthe proximal third of radius

o it supinates the forearm, turning the arm to face anand superiorly when the forearm is flexed. It is thePRIME MOVER for slow unopposed suination

o The supinator forms the floor of the cubital fossa twith brachialis. It is a sheet-like muscle, and it envthe radius.

Extensor Indiciso Posterior interosseous nerve o originates from the posterior surface of the distal t

the ulna, and the interosseous membraneo inserts into the extensor expansion of the index fino extends the index finger, enabling independent exto helps extend the hand at the wrist

"outcropping" deep layerthese originate from the proximal, middle and distal thirds of the ulna (as ageneralization). They emerge in the surface in the furrow that forms in theextensor compartment

Abductor Pollicis Longuso Posterior interosseous nerve o originates from the posterior surface of theproxima

radius and ulna, as well as the interosseous membo inserts into the base of the 1st metacarpal, and

occasionally also the trapezium.o abducts and extends the thumb at the carpometaca

jointo shares a common tendon sheath with the extensor

pollicis brevis at the wrist

Extensor Pollicis Breviso Posterior interosseous nerve o

originates from the posterior surface of thedistal ththe ulna, and the interosseous membraneo inserts into the dorsum of the base of the proximal

phalanx of the thumbo extends the proximal phalanx of the thumb at the

metacarpophalangeal joint; also extends thecarpometacarpal joints of the thumb.

o partly covered by the abductor pollicis longuso its tendon is immediately medial to the APLo these two tendons form the anterior boundary of th

anatomical snuffbox.

Extensor Pollicis Longuso Posterior interosseous nerve o originates from the posterior surface of themiddle t

of the ulna, and the interosseous membraneo inserts into the dorsum of the base of the distal pha

of the thumbo extends the distal phalanx of the thumb; also exte

the metacarpophalangeal and the carpometacarpalof the thumb. It also rotates the thumb laterally.

o It enjoys its own tendon sheath at the wrist; it passmedially over the dorsal tubercle of radius, using ipulley.

o the EPL forms the posterior border of the anatomicsnuffbox

Supinator

Attachments of the Supinator t o the Epicondyle of humerus Radial collateral ligament Annular ligament of radiusUlnar Supinator crest and fossaUlnar posterior surface

Abductor polli cis longus

Extensor Pollici s Longus

Extensor Polli cis Brevis

I nterosseous membr ane

Ext ensor I ndicesWhich shares an extensor

tendon sheath with theExt ensor Digi torum tendon

Common sheath for thetendons of the extensor

pollicis brevis and abductor pollicis longus

APL in ser ts into th e base of 1 st metacarpalEPB in sert s in to the base of proximal phalanxEPL in ser ts in to the base of di stal phal anx

the Supinator wraps around theradius to insert into the anterior surface of it. Together with thebrachialis it forms the floor ofthe cubital fossa

Extensor di gitorum tendon Extensor expansion

M edial band attaches to the base ofthe middle phalanx

L ateral bands attach to thebase of the distal phalanx

The hood which attaches to the palmar tendon


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Flexor and Extensor Tendons at the Wrist: level of the Distal Radioulnar Joint

- attaches

Palmari s Longu s Ready to merge with the palmar aponeurosis

M edian N erveUln ar Artery

Ulnar nerve

Fl exor Carpi Ulnari s can cover the ulnarartery and obscure its pulsation


Fl exor Poll icis Longus

Radial Ar tery

Abductor Polli cis Longus

Extensor Polli cis Brevis

Extensor Carpi Radiali s Longus

Extensor Carpi Radiali s Br evis

Ext ensor Poll icis Longus

Extensor I ndices

Extensor D igitorum

Extensor Digiti M inimi

Extensor Carpi Ulnar is

Fl exor Di gitorum Superfi cialisFl exor Digitorum Profu ndus

R R AAD D I I U U S S

U U LL N N AA

The Extensor Retinaculum- Attaches to the lateral border of the radius - Does NOT attach to the border of the ulna, because the ulna moves too much. - Instead, attaches to the pisiform and the triquetrum - Also attaches to the ridges of the radius, thus forming osseofibrous tunnels for the above tendons to run

through - There are 6 tunnels in total:

1. One for abductor pollicis longus and extensor pollicis brevis 2. One for extensor carpi radialis longus and extensor carpi radialis brevis 3. One for extensor pollicis longus

4. One for extensor digitorum and extensor indices 5. One for extensor digiti minimi 6. One for extensor carpi ulnaris


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The Flexor retinaculum is stretched between foubony posts:

1) Hook of hamate2) Pisiform bone3) Tuberosity of scaphoid4) Tuberosity of trapezium

The Carpal Tunnel and its Contents

Radial ArteryCrossing over to thedorsum of the hand

Abductor Polli cis Longus

Ext ensor Poll icis Br evis

Extensor Carpi Radiali s Longu s

Extensor Carpi Radiali s Br evis

Ext ensor Poll icis Longus

Extensor Digiti mini mi

Palmari s Longus

Thenar musclesH ypothenar muscles

Extensor D igitorumExt ensor I ndices

Extensor Carpi Uln aris

TRAPEZIUM

TRAPEZOID

CAPITATE

HAMATE

Uln ar Artery

Uln ar Nerve

Fl exor retinaculumM edian N erve

Fl exor Digitorum Pr ofundus

Fl exor Digitoru mSuperficialis


Fl exor Poll icis Longus

Hook of HamateTuberosity ofTrapezium

Tuberosityof Scaphoid

Pisifo

This is a narrow enclosed space. Needless to say, if anything in here swells, the median nerve will getcompressed. It is the most sensitive structure in the carpal tunnel.

- The lateral three and a half digits will get diminished sensation- Sensation on the thenar eminence will be spared because the palmar cutaneous branch splits

from the median nerve long before the flexor retinaculum- The movement of the thenar muscles is controlled by a terminal motor branch of the median nerve,

and so the thenar muscles will atrophy in carpal tunnel syndrome


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A Summary of the Innervation of the Extensors and Flexors of the Forearm

xtensors All innervated by branches of the RADIAL NERVERadial nerve itself: innervates muscles with attachments proximal tothe cubital fossa

- Brachioradialis- Extensor Carpi Radialis Longus - Both of these originate at the supracondylar ridge

Deep branch of the radial nerve: a branch which splits off fromthe radial nerve at the level of the humeral condyle in the cubital fossa; itpierces the supinator muscle, and becomes the posterior interosseous nerve

- Extensor Carpi Radialis Brevis- Supinator

Posterior interosseous nerve: travels along the posterior aspectof the interosseous membrane; innervates most of the extensor muscles

- Extensor digitorum- Extensor Indicis- Extensor Digiti minimi- Extensor Carpi Ulnaris- Extensor Pollicis Longus- Extensor Pollicis Brevis- Abductor Pollicis Longus

FlexorsInnervated by either the ULNAR or the MEDIAN nervesMedian nerve itself:

- Pronator Teres- Palmaris Longus- Flexor carpi Radialis- Flexor Digitorum Superficialis

Anterior interosseous nerve , a branch of the median nerve: - Flexor Digitorum Profundus - lateral half- Flexor Pollicis Longus- Pronator Quadratus

Ulnar nerve:- Flexor Digitorum profundus, only the medial half - Flexor Carpi Ulnaris

Deep branch ofthe radial n erveis in pink

Radial nerve is in r ed

Posteri or i nterosseous nerve is in gr een

Uln ar nerve : Innervates the musclesdirectly adjacent to it alongits course down the arm

M edian nerve: Innervates mainly the 1 st and 2 nd layer of flexors

Ant erior I nerosseousnerve: innervates the 3deepest muscles


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Fascia, Septa, Tendon Sheaths and the Potential Spaces of the Hand These fascial layers are continuous withthe fascial sleeve of the forearm.Centrally the fascia of the palm thickensin the centre, where the palmarislongs tendon attaches to it, which isalso where it merges with the flexorretinaculum. This whole thickened

area is called the palmar aponeurosis.Distally, the palmar aponeurosis dividesinto four bands which attach to thebases of the proximal phalanges, andthere it becomes a part of thedigital sheaths

Palmari s Longu s tendon

Ant ebrachial F ascia

Fl exor retinaculum

Al l merge int o thePalmar A poneur osis

Palmar Aponeur osis so thick and tough that any infectionin the palmar spaces will actuallycause the weaker DORSAL fascia tobulge out.

In Dupuytren’s contracture, the palmar aponeurosis becomes nodula

ibrosed, and thickened Thenar f ascia

H ypothenar f ascia

Palmar A poneur osis

Lateral f ibrou s septum of the palmwhich stretches from the palmaraponeurosis to the 3 rd metacarpal

M edial f ibr ous septum ofthe palm which stretches from the palmaraponeurosis to the 5 th metacarpal

The Thenar Space

Of the two septa, the LAT ERA L is the strongest

The M idpalmar SpaceUnlike the thenar

space, this one iscontinuous with thanterior compartmof the forearm- itcommunicates witvia the carpal tunn

Common f lexor sheath: F DS and FD P

The common f lexor sheath continu es to the

5 th

digit. T he other digits have their ownDi gital Synovial Sheaths

Di gital Synovial Sheat

Synovial sheath for F lexorPolli cis Longu s

Synovial sheath for F lexorCarpi Radialis


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Compartments of the palm and their contents

Thenar compartmentContains the thenar muscles

Central compartmentContains the flexor tendons and theirsheaths, the lumbricals, the superficialarterial palmar arch, and the digitalvessels and nerves

Hypothenar compartmentContains the hypothenar muscles

Adductor compartmentContains only Adductor Pollicis

Interosseous compartmentsContains the interossei muscles

Fl exor Pollicis Br evis: Superf icial headwhich is innervated by the MEDIAN NERVE

Deep Head which is innervated by the DEEP BRANCH OF THE ULNAR NERVE

Abductor Pollicis Br evis

Opponens Polli cis

1 st

Dor sal I nteroissei

2 nd Dor sal Int eroissei

3 rd Dor sal I nteroissei

4 th Dor sal I nteroissei

1 st Palmar I nteroissei 2 nd Palmar I nteroissei

3 rd Palmar I nteroissei

Abductor Digiti M inimi

Flexor Digiti M inimi Br evis

Opponens Digiti M inimi

1 st and 2 nd Lu mbricals which are unipennate and which areinnervated b the MEDIAN NERVE3 rd and 4 th Lu mbricals which are bipennate and which areinnervated by the DEEP BRANCH OF THE ULNAR NERVE

Adductor Polli cis

Thenar Compartment

Adductor compartment

I nterosseous compartment

HypothenarCompartment

CentralCompartment


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Thenar and Hypothenar muscles There are 3 Thenar muscles, 3 Hypothenar muscles, 1 Adductor muscle, 4 Lumbricals, 4 dorsal interossei and 3 palmar inteross

Hypothenar MusclesIn the HYPOTHENAR compartment

Opponens Digiti Minimio deep branch of ULNAR NERVE o

originates from hook of hamate and the flexor retinaculumo inserts into the medial border of the 5th metacarpalo pulls the 5 th metacarpal anteriorly, and rotates the 5 th digit so

it can participate in opposition with the thumbo acts exclusively at the MCP joint

Flexor Digiti Minimi Breviso deep branch of ULNAR NERVE o originates from hook of hamate and the flexor retinaculumo inserts into the medial side of the base of the 5th proximal

phalanxo flexes the proximal phalanx of the 5 th digit

Abductor digiti Minimio deep branch of ULNAR NERVE o originates from the pisiformo inserts into the medial surface of the bae of the 5th proximal

phalanxo Abducts the 5

th digit and assists in its flexion

o It is the most superficial of the three hypothenar muscles

Thenar MusclesIn the ADDUCTOR compartment

Adductor Polliciso deep branch of the Ulnar nerve

- TRANSVERSE HEAD originates from the anterior surface of thmetacarpal- OBLIQUE HEADoriginates from the bases of the 2nd and 3rd

metacarpals, from the capitate bone, and from any carpals aroucapitate.

- Inserts into the medial side of the base of proximal phalanx of There tends to be a sesamoid bone at the site of insertion.

- Adducts the thumb towards the lateral border of the palm (presit against the palm)

In the THENAR compartment Flexor Pollicis Brevis

o DEEP HEAD: deep branch of ULNAR NERVE o SUPERFICIAL HEAD:Recurrent branch of MEDIAN NEo originates from the flexor retinaculum and the tubercles

scaphoid and trapezium.o Inserts into the lateral aspect of the base of the proximal

of the thumbo Flexes the thumb: brings its tip towards the base of pinky

Abductor Pollicis Brevis: Recurrent branch of MEDIAN No originates from the flexor retinaculum and the tubercles

scaphoid and trapezium.o Inserts into the lateral aspect of the base of the proximal

of the thumbo Abducts and helps oppose the thumb

Opponens Pollicis Brevis: Recurrent b. of MEDIAN NERo originates from the flexor retinaculum and the tubercles

scaphoid and trapezium; Inserts into the lateral side of thmetacarpal.

o Opposes the thumb: medially rotates and the pulls media1st metacarpal. Acts exclusively at the MCP joint

ADDU CTOR POLLI CIS, which has2 heads, between the origi ns of whi ch theRADIAL ARTERY emerges to form thedeep palmar arch

Tran sverse head of A dductor Poll icics,which originates from the 3 rd me

Obliqu e head of Adductor Pol li cics,

which originates from the 3rd

meas well as from the 2 nd metacarpacapitate bone, and all adjacent carpabones

Adductor pollicis inserts into the latepart of the 1 st proximal phalanx

Fl exor poll icis brevis with two heads superficial and the deep. The deep headinnervated by the deep branch of the ulnnerve

Opponens Poll icis

Abductor Pollicis Br evis

Both of these muscles ori ginate fr om thefl exor retinaculu m and the tubercl es of

scaphoid and trapezium ; they both i nsertin to the lat eral aspect of the base of theproximal phalanx of the thumb.

Al so or igin ates fr om the fl exorretinacul um and th e tubercl es of scaphoid and trapezium ;however it inserts into the lateral border of th e 1 st metacar

Fl exor retinaculum

Abductor Digiti M inimiWhich originates at the

pisiform and inserts into themedial side of the base ofbase of 5 th proximal phalanx

Flexor D igiti M inimi BrevisWhich originates from the flexorretinaculum and the hook ofhamate, and inserts into the

medial side of the base of the 5th

proximal phalanx

Opponens Digiti M inimiWhich originates from thelexor retinaculum and the

hook of hamate, and insertsinto the medial border ofthe 5 th metacarpal

Th ere is also Palmar is Brevis; a useless little muscle which wrinklesthe skin of the palm; it originates at the flexor retinaculum and inserts

into the skin. The ulnar nerve innervates it.IT I S NOT PART OF TH E HYPOTHENAR COMPARTMENT


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Short muscles of the Hand o there are 4 lumbricals, 4 dorsal interossei, and 3 palmar interossei; you count them starting at the THUMB

The LUMBRICALS- Originate from the tendons of theFLEXOR DIGITORUM PROFU- Sit in the central compartment of the palm- From the palm, cross over to the dorsum of the hand - Insert into the extensor expansions on the dorsum of the proximal

phalanges

- The FIRST and SECOND lumbricals are innervated by the mediannerve. All other short muscles are innervated by the deep branch oulnar nerve

- The THIRD and FOURTH lumbricals are bipennate; the other twounipennate

- FLEX the metacarpophalangeal joints - EXTEND the proximal interphalangeal joints

The DORSAL INTEROSSEI - Originate from the sides of two metacarpals (ALL of them are bipennate) - Sit in their own INTEROSSEOUS compartment of the hand- Insert into the bases of the proximal phalanges and into the extensor

expansions - ABDUCT the hand away from the axis of the middle finger (the axis as

shown)-hence “DAB” (“Dorsal Interosei ABduct”) - Also help the lumbricals flex the MCPs and extend the PIPs - When the thumb is flexed, the first dorsal interossei can be seen as the

lump that appears on the dorsum of the hand.

The PALMAR INTEROSSEI - Originate from the palmar surfaces of the metacarpals - Sit in the anterior part of the INTEROSSEOUS compartment of the hand- Inset into the bases of the proximal phalanxes and into the extensor

expansions- ADDUCT the fingers towards the middle finger,

hence “PAD”- Palmar Interossei Adduct- There are only 3 palmar interossei; the deep part of the Flexor Pollicis

Brevis can be described as the 4th, because it does much the samething as the rest, and is innervated by the same nerve

The I nterossei all li ve inside the I NT EROSSEOUS compartment. The Palmarin terossei occupy the anterior (palmar )part of it, and th e dorsal in terossei ar emore pr oper ly between the metacarpals.

Together the shor t muscles all produc e the “Z” movement of the fingers; the MCPs aref lexed, and the PIPs extended. Th is is the opposite of wh at happens in ul nar nerve palsy(“claw hand”) when the MCPs are extended and the PIPs are flexed.

References : Moore’s Clinically Oriented Anatomy 5 th

e d i t i o n

anatomy - upper limb - 3 muscles, innervation and compartments of the upper limb

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